Largest 124 radiator.

[WDB124066]

Car was set for hot air intake straight off the fan tips!!

Now has the correct shroud for ambient air intake around the back of the headlight. Will need a hot day in slow traffic to see what difference that makes. !!

Might need to adjust the fuel mix too...

 

[brucemillar]

OK. Not a thread hi-jack here. My smugness with my Pajero temps was short lived. Last week I hit traffic on a very steep hill. Temp started to increase fairly rapidly after being stood for around 5 minutes. It hit 115c This is not good.

I had had my AC re-gassed a few days before. So now the AC was working correctly. Checks revealed the AC electric fan was not working at all. A volt meter showed that the fan was being energised (it switches on an earth). But the fan was dead. Bought a 14"electric motorsport fan which is fully reversible for push or pull. Fitted it yesterday using the existing wiring harness and some solder. Job done.

My AC Rad sits over the front of the engine rad. I guess in cooler temps this is not an issue. Or if not using the AC. But with both in play it causes a hefty temp gain.

The fan was £22 on ebay: Universal Slim Electric Radiator Fan 8 9 10 12 14 Inch Kit Project Track Car | eBay

 

[WDB124066]

Just measured 77 Deg C intake air temp at filter box inlet with engine temp only at 95 Deg C.

It's been sucking in a lot of hot air! Runs much better now.

 

[hotrodder]

Didn't know a hot air/winter air pick up existed for them or is that done by just leaving the headlamp duct off? Fuelling etc will take care of itself

 

[WDB124066]

That is indeed how it's done. Notice just how close the inlet is to the fan tips - placed perfectly for hot air in very cold conditions.

It is a very easy piece of plastic to leave off.

I don't have cats or sensors, I need to set my fuel manually from time to time....

 

[WDB124066]

I'd have thought things like valve timing or compression ratio from skimming too much would have other effects beyond running hot when idling only? Partially blocked/gumed up water passages fit though

Only thermostat and coolant 'cause it'd be mad not to at the same time. Oh, and maybe the aux belt tensioner/some idlers
Bought the old barge with ~178k on it, hit properly massive delays driving it home down the M1 (the really annoying sort where traffic is constant stop/start crawling so can't just switch off and chill) and the viscous fan kept the thing cycling between mid-high nineties and just over 100° the entire time. Heater wasn't really on and it's fan was dead so wouldn't do much to lower temps anyway

About a year later the temp would start climbing pretty quickly when stopped at lights etc after leaving a motorway. This was accompanied by a small and (initially) tricky to spot coolant leak as the pump was weeping. By the time i got around to changing the pump the leak was a chunk worse and the car would mark it's territory when parked up with a steady drip from the pump pulley. You could charge up and down motorways at *cough* mph with it sitting at a steady 85ish °, it was only in stop/start traffic it struggled to stay cool and relied heavily on its fans

New pump and the running temp was waaaaay more stable in traffic. Couple of years after that the origional rad started weeping and with a new rad in it temps were even more stable... can't remember the last time the viscous fan has cut in, with the 20 - 22°C ambient temps we currently have 15 - 20mins of stop/start crawling along the A20 would get the temp upto maybe 95ish°

No doubt it's possible to get air locks (managing to fit the 'stat the wrong way so it's bleed hole isn't at the top?) but IME the m104 self bleeds really quickly as long as the heater is set to max... no bleed points to play with, just run the engine and top the coolant up as the level drops

Nicked a couple of pics from the internet and overlayed them to show how the gasket meters/restricts flow from the block to the head in most areas other than the back of the engine

View attachment 58728

Blockages/corrosion around the waterways circled in green would be bad as would enlarging the small vent holes to match the passages in the block and head

I can't see temp surveys telling much about the waterpump... if it's to blame it'll be something that messes with its efficiency like wobbly bearings, a mickey mouse impeller etc. 'Cause it's simpler/faster than pulling the head off again i'd probably slip the belt off to see if there's any play in the pump and if that checks out dump the coolant and have a poke around with a bore scope after removing the 'stat

Apart from the 2 and 3 mm holes are those green circled holes in the CHG the only way water is supposed to get to the head - the rest of the holes being head studs or oil drain holes...?

I think this picture answers the question. Looks like the tiny holes are selected carefully to control flow of water to the head as they progressively get very slightly larger toward the rear - the whiter areas being the coolant whetted areas. If the hole sizes are that critical that 1 mm step increments are made I'd suspect a blockage around a few of them may be the cause of my problem.
Car is better since I got cold air in but it still overheats above 23 DegC ambient.

There are approx 33 holes in that CHG that are 3 mm or less in diameter, looking at that it's clearly important to keep the system scrupulously clean, especially keeping old CHG material out of the system.

I've got a feeling rorf may have been correct in that the head really does need to come off to be sure.

 

[hotrodder]

Apart from the 2 and 3 mm holes are those green circled holes in the CHG the only way water is supposed to get to the head - the rest of the holes being head studs or oil drain holes...?

I didn't circle them all in that pic, just highlighted the main ones at the back of the engine. Like you say

I think this picture answers the question. Looks like the tiny holes are selected carefully to control flow of water to the head as they progressively get very slightly larger toward the rear - the whiter areas being the coolant whetted areas. If the hole sizes are that critical that 1 mm step increments are made I'd suspect a blockage around a few of them may be the cause of my problem.
Car is better since I got cold air in but it still overheats above 23 DegC ambient.

There are approx 33 holes in that CHG that are 3 mm or less in diameter, looking at that it's clearly important to keep the system scrupulously clean, especially keeping old CHG material out of the system.

I've got a feeling rorf may have been correct in that the head really does need to come off to be sure.

many of them are tiny by design to control flow... waterpump shoves coolant from the front to the back of the block, if the gasket matched the 'as cast' shape of the water passages much of the coolant would take a short cut over cooling the front cylinders while the back of the engine cooked. Small holes in the gasket are mostly for bleeding any air out, some of them get bigger towards the back with 3 larger ones right at the back so that the bulk of the flow comes up into the head from the back and then forwards to the 'stat and so on. The holes that most noticably get larger are near the exhaust ports, i'm guessing they only bother enlarging the rear hole for each cylinder because the bulk coolant flow wants to be front to back of block, up and then forwards through the head

Still not done them all but highlighted more coolant holes as your gasket pic is better/larger...



and nicked another block pic (this time with rust stains in the water passages) as it makes it easier to see which are bolt holes, oil passages etc



The small holes in the head gasket thing is pretty much universal, i'm currently part way through drawing a copper gasket for some old Renault Alpine (A110 i think) and it's even more noticable as the engine is an 'open deck' design (cheaper, not as stiff/strong) so mostly open space when looking at the block deck

While pulling the head is about the only way to really see what's going personally i'd flush the thing with citric acid (or vinegar, weak acetic acid) first... yeah i know that some claim not for an m104 as they have a magical anti corrosion coating but any coatings were done at least 20 years ago and if the coating has survived that long i can't see a quick spin with a weak citric or acetic acid solution instantly stripping it. Either will be very good at eating any scale or rust though including any bits that are blocking smaller gasket holes

 

[WDB124066]

Thank you most kindly hotrodder, my thoughts below, comments most welcome...


I won't use acid in the system, have read up corrosion mechanisms and can understand precisely why it can help corrosion significantly.

I need to get the old CHG material out that I feel is most likely sitting in the block passages beneath those holes. Much of it won't get past the small holes and the bits that do will find their way round the system till they eventually get stuck there again. I have a feeling those holes are the smallest passage in the system, smaller than the rad and heater exchanger passages.

Does the CHG material float or sink?

If it sinks how best to get it out, can you vacuum with a small tube down the galleries and reach it all? I don't trust using just the drain. Otherwise you'd have to back flush the system i.e. reverse the flow and force the bits out of the drain, is this even possible?

I think those holes have a duel purpose, not only do they bleed air but they control flow, like you say more flow at the back. There are so many of them that if only a few become blocked you'd only expect a very small increase in temp as the flow drops [possibly not even noticeable on the temp gauge], as more and more become blocked that's when you'd notice a significant increase in coolant temp and hot spotting that you may not notice on the gauge at all.

If the pump or lack of flotation shifts the debris around a bit this could explain why sometimes the system behaves normally for short periods before it reverts to being a problem - again.

Wonder if I can get a filter in the system between the pump and the head to block connection similar to what the oil system has, seems to me with lots of 1.5 mm holes the coolant system is just as likely to block as the oil system would be if it didn't have a filter. For many reasons particle sizes in the coolant system are going to be much larger than the oil system.

 

[hotrodder]

If you use genuine MB coolant (or generic g48 stuff) then the cooling system already contains acid salts as ethylhexanoic acid is one of the corrosion inhibitors used, MSDS for MB G48 coolant... http://www.worldpac.com/tagged/MBZ_ANTIFREEZE_G48.pdf

Google 'ammoniated citric acid boilers' and you'll get a bunch of hits related to the cleaning, descaling and passivating industrial boilers. Even without ammonia to raise the pH citric doesn't noticably attack 'good' iron or steel even if parts are left soaking in the stuff for days after it's stopped actively reacting (fizzing away as it reacts with iron oxides and turns into soluble iron citrate). The only time i've ever heard of it 'helping corrosion' is when people have then scrubbed the part shiny, rinsed it and then wondered why it flash rusted when left to dry naturally

I haven't got a before pic as i only took this one when someone was claiming that citric would etch steels but FWIW



is a Dickson lathe tool holder that was properly rusty when i aquired it so got dumped in a bucket of citric overnight. Resized pic doesn't help but can still see origional machining marks on it along with the (now clean) pitting from when it was covered in rust. If i'd attacked it with wire brushes and gotten it properly shiny after it's citric bath it'd have rusted again hence just wiping it over with an oily rag. Obviously with a cooling system you just flush it out again with copius amounts of clean water and then immediately fill it with fresh coolant

This is why citric acid is the main active ingredient in lots of rust removers along with many other cleaners, especially those aimed at descaling stuff, cleaning up hard water stains

Dunno whether bits of h/gasket float or sink but i'd have thought if bits of gasket are the problem, or at least part of it, it'd be pieces stuck in coolant passages rather than small bits floating about blocking the smaller vent/bleed holes in the gasket?
I'd have thought blockage of some or even most of the small holes in the gasket would have a minor, if any, noticable effect on running temp? Partial blockage of the larger passages is more likely to effect overall running temp IMO, the smaller vent holes might locally increase temps* but not the average water temp which is what the gauge displays

Flushing (either with chemicals or pressure/reversing flow) usually deals with most small stuff/sludge/scale. If there is larger chunks of gasket or sealant partially blocking things from sloppy workmanship when the gasket was changed and it's wedged in somewhere then it's probably down to luck... flushing backwards (disconnect hoses, knock up fittings so water and/or air can be forced through the wrong way) with some decent pressure might help dislodge things If a bit of gasket etc is properly wedged in somewhere might need lots of luck to find it and fish it out like Bruce had... http://www.mbclub.co.uk/forums/engine/212136-coolant-temps-what-should-they-2.html#post2331077

Personally i don't see much advantage to filtering the cooling system, the oil system needs it because bearing clearances are miniscule compared to small water passages/gasket holes and tiny bits of metal can score bearing surfaces etc. I'd have thougt small bits floating about in the cooling systen are rarely gonna block things up permantly due to vibration etc? Scale/corrosion messing with heat transfer is usually a bigger deal for the cooling system and one that's only really fixable with chemical flushes if/when scale build up etc happens

* the sort of thing that might be picked up by checking temps of the manifold primarys/head by the exhaust ports or by reading plugs if one or two pots are running hot?

 

[WDB124066]

There is a column of water below those small holes that can't flow upwards due to the hole being blocked, I imagine the column is roughly the length of the cylinder. Clearly by stepping the size of the very small holes at the top of the column up by 0.5 or 1.0 mm at a time towards the rear, they are supposed to enable flow, which, is controlled very closely by the fact that the holes are adjusted for size very precisely. If you block enough of them you get no flow around the cylinders except for through the three large holes at the right rear. That will lead to trouble. I feel those holes are the smallest aperture in the system and as such it makes a whole lot of sense to me that that is where you could expect debris to collect.

The car is not displaying normal temps at all. There was a huge step change in performance after the CHG job, didn't get 30 kms without having to park up on the side of the road sitting at 118. And I'm not the only one from the shop who has experienced a problem after a CHG job. They tell me three others all display exactly the same symptoms.

Reducing the inlet temps through proper ducting has helped. But over approx 23 Deg C ambient and the heat transfer [through delta T] means you need to progress beyond 120 Deg C to balance the system. Simply it can’t cope with the amount of heat it has to dissipate.

The cooling system has next to no rust or scale inside, it is clean. I will not use acid unless MB says so. Just to confirm this, I tried discussing the problem with a new Dealership just in case the Tech I normally use had it wrong. The VERY first question I was asked by their Workshop Forman was "did you use any acid in the system". I said "no" he said "well done don't use it". That's two very senior old school been in the Dealership network for years types that have said the same thing. They also said in their experience from the information I gave them that it is most likely a circulation problem. So I started looking at the circuit and saw the tiny holes at the top of a column of water.....

Heat transfer out of the metal doesn't seem to be a problem because my coolant temp is high - too high [although I have no idea what the oil temps are]. The problem is getting the heat out of the coolant.
I am familiar with the electrochemical phase diagrams first discovered by Pourbaix, and boiler feed water treatment. You only need to descale if the system is not looked after and results in corrosion. MB have no descale method for the M104 because if you look after it the way they say there will be no appreciable corrosion. Do something else and you are on your own.

I'd be really interested in your thoughts about the column of water without the hole in the top and what effect that would have. I have no block here to see what those galleries look like unfortunately.

 

[rorf]

As I said awhile back it is now time to remove the cylinder head again. Before you did the HG you had no problems, now you do.

Bigger radiators etc etc will not solve the problem.

Take it to a decent workshop who must have the head crack tested etc and to use the correct head gasket with no sealants etc.

Continual overheating will just do more and more damage to the engine - good luck.

 

[LvR]

As Bruce said. Bulk coolant flow through the rad is like



and you're just looking for hot or cold spots really. Temp drop across the rad should be somewhere in the ballpark of 15 - 20° once the engine is upto operating temp i'd have thought off the top of my head*.

My first post here, but imo that info/suggested measurement by Bruce/hotrodder is still lacking (maybe I just missed it?) despite the age of the thread/problem

During one of your "overheating" episodes, - What is the exact temp of the inlet end outlet pipes on the radiator - say 10mm or so from rad?

If you are not close to about that differential range across the whole of the radiator in Celcius AT AROUND THE NORMAL ENGINE RUNNING TEMP you have a problem with getting heat out of the coolant in the radiator and and into the surrounding air.

Before yanking the head again I would suggest you maybe do this particular measurement first.

 

[WDB124066]

As I said awhile back it is now time to remove the cylinder head again. Before you did the HG you had no problems, now you do.

Bigger radiators etc etc will not solve the problem.

Take it to a decent workshop who must have the head crack tested etc and to use the correct head gasket with no sealants etc.

Continual overheating will just do more and more damage to the engine - good luck.

I think so too to be frank.

Agreed.

It is not loosing coolant, cracked head would loose coolant. But, I will look to have it measured for flatness. Actually just thinking about this it may pay to have it examined for cracks and loss of compression before it comes off. What is the difference between a leak down test and a compression test - and what would be best for this situation...?

Agreed.

 

[WDB124066]

My first post here, but imo that info/suggested measurement by Bruce/hotrodder is still lacking (maybe I just missed it?) despite the age of the thread/problem

During one of your "overheating" episodes, - What is the exact temp of the inlet end outlet pipes on the radiator - say 10mm or so from rad?

If you are not close to about that differential range across the whole of the radiator in Celcius AT AROUND THE NORMAL ENGINE RUNNING TEMP you have a problem with getting heat out of the coolant in the radiator and and into the surrounding air.

Before yanking the head again I would suggest you maybe do this particular measurement first.

Agreed. Car is back at my winter home now, I will look to gather this data in the next few days and report back accordingly.

Just done 400 plus Kms at night on the open road, the gauge never went above 100 DegC, there is no water in the oil and no loss of coolant, but I do have an oil leak from the engine that is new today. Will look to find the source of this in the next wee while.

Many thanks to all for your input, it is very much appreciated.

W.

 

[WDB124066]

Got it.

How to do Cylinder Leak Down Testing - Hot Rod Network

 

[LvR]

Have not seen this asked either ....................

AT or manual?

If AT, then AT normally has an AT tank added onto the radiator ........... perhaps in town driving (when eg the torque converter isn’t locking up) the box, due to age, is generating so much additional heat load the radiator is simply unable to get rid of that too?


And....

With an ambient of say 15 to 20C - how long before your temp gauge register about 5C from the thermostat rating temp from first cold start-up? IMO if all is working as it should you should have a normal operating temp indication within about 3 to 5 km. I am thinking that some thermostats not only open certain passages to allow water to circulate through the radiator but also keeps other passages closed/restricted so as to prevent coolant circulation when engine is cold....................and depending on the mechanical tolerances of items used in the construction of the thermostat even a new but wonky thermostat (or incorrectly fitted) could prevent some of the coolant from actually circulating through the engine.

Tangent thought - some person didn’t perhaps bypass the in-car heater core when the HG was done? ................. depending on how such things are done it could screw the pooch on the liquid circulation properties through the engine

 

[hotrodder]

W124s predate lock up torque converters. The transcooler in the rad should really be called a heat exchanger [/pedantic] as a large part of it's job is to help warm up atf (sitting in traffic, low speed driving etc) as well as cool it when the 'box is working hard (towing, driving up mountains etc). Same deal with the engine oil cooler on these engines, it's a water to oil heat exchanger that helps warm the oil a lot of the time and cools it other times. In both cases the aim is to keep the oil within a narrower operating temp range than is commonly achieved with seperate air-oil coolers

It's a dual valve / bypass type 'stat on these i.e. 'stat closed and the coolant is shunted directly into the pump (they're part of the same casting) and sent back around the engine. As the stat begins to open to send coolant through the rad the bypass port is gradually closed at the same time. When the stat is partially open (most of the time when everything is working properly) the waterpump is giving the engine a mix of coolant that's bypassed the rad and coolant that's been shunted through the rad. If/when the stat is fully open the bypass is closed to divert all the coolant through the rad
The waterpump chucks most of the coolant into the block but also has a bleed that sends some through the engine oil heat exchanger by/built into the oil filter before it joins the bulk flow at the back of the block
IIRC the heater outlet dumps coolant back into the pump inlet. There's a small leccy booster pump between the head and heater with the 'duo valve' (or monovalve with automatic climate) used to control flow through the heater according to heater settings & cabin temp

There is a column of water below those small holes that can't flow upwards due to the hole being blocked, I imagine the column is roughly the length of the cylinder. Clearly by stepping the size of the very small holes at the top of the column up by 0.5 or 1.0 mm at a time towards the rear, they are supposed to enable flow, which, is controlled very closely by the fact that the holes are adjusted for size very precisely. If you block enough of them you get no flow around the cylinders except for through the three large holes at the right rear. That will lead to trouble. I feel those holes are the smallest aperture in the system and as such it makes a whole lot of sense to me that that is where you could expect debris to collect.

I'd be really interested in your thoughts about the column of water without the hole in the top and what effect that would have. I have no block here to see what those galleries look like unfortunately.

They aren't individual columns of water / small water jackets linked by small passages. Under the deck it's one open space around the cylinders. Open, semi open and closed deck block differences are shown here Supporting Your Cylinders - Open, Semi-Closed, Or Closed Deck? The closed deck example in that link was done by pressing material into place to add some more support to the top of the cylinders. CI blocks like the m104 are cast this way, can get rough idea of how thick (not very) the deck is from this pic as the angle is just right to see how the water jacket opens up a bit below the surface



The holes in the deck need to be left relatively large to get casting sand/mold cores out after the block is cast. The smallest coolant holes in the gasket are mostly for venting any air pockets/bubbles. Bleeding a small amount of cooler coolant obviously helps even out temps because if all of it was pushed to the back of the block and then forwards through the head the front few combustion chambers are likely to run a bit hotter than the rears.

Personally i can't see a few 1.5mm ish holes being able to flow enough coolant to account for the temps you're seeing... the rad has a small bleed hose that vents any air back to the header tank and helps the system self bleed, this is about 5 or 6mm ID and not much coolant flows through this i.e. at this time of year (single digit temps in the UK) the header tank in mine will be cool to touch for quite some time after the engine is upto running temp and the top rad hose is hot. Blocking a bunch of them can't directly mess up overall coolant flow rates significantly IMO. In theory could result in air locks and localised overheating but between engine vibration and uphill/downhill/cornering any air should still find it's way out due to the layout of the block waterjacket below the deck i'd have thought

We're obviously never gonna agree about flushing chemicals so my last comments about that... the MB guys that are totally against it, they're the same ones that changed the gasket last time which is what started the overheating problems? It was changed because of the usual external oil leaks this engine is infamous for? You've not had a close look at the block to see how the coolant passages are layed out but are certain that there's no scale or corrosion to speak of?

Missed it last time around but re reading the thread this

I don't have cats or sensors, I need to set my fuel manually from time to time....

jumped out at me. An e320 w124 with an m104 should be Bosch Motronic / HFM-SFI engine management. Regardless of local environmental rules about cats an O2 sensor in the exhaust is a fundemental part of the system and most aftermarket management whether MAP, MAF or alpha N based. I can't get my head around why you'd need to set the fuel manually from time to time (what about ign timing?) and if there's no closed loop adaption how do you know the overheating isn't related to excessive combustion chamber temps?

 

[LvR]

cheers for the stat and AT detail hotrodder

 

[LvR]

Problem is the needle is not stable, it is up and down all the time relying on the VC cutting in to bring it down or the over pressure electric fan to do the same. It has gotten to the point where it is spitting out refrigerant because it gets too hot, that drops the refrig pressure which then removes the overpressure triggered fan and we rely on the over temp electric fans - what a noise they make @ 107! They do the job nicely but that needle on the dash just goes up and down up and down all day. It does not want to stabilise and sit steady in traffic at all.

I obviously don’t know these particular motors so please excuse me demonstrating the fact - anybody able to set me straight if my engine cooling 101 classes are failing me? ..................

What is an " over pressure electric fan" as found/mentioned here and why would that be a desirable method of controlling temperatures of engine cooling?. IMO one cannot have an overpressure (in the cooling system anyway) situation as long as your radiator/expansion tank cap pressure has been properly chosen (the assumption has to be made that the general about 0.9 to 1.1 Bar rated pressure caps as used on other cars all over the world is also used on this model)

Perhaps I am assuming the wrong location for the animal and its perhaps located on the AC high pressure line? .................... in which case, if you ever end up spitting "refrigerant" from THAT system as mentioned, the technician recharging the AC needs a swift kick up his backside?

 

[LvR]

Thinking about this " over pressure electric fan" thing.............

Most all modern (1985+?) vehicles have electric AC cooling fans on the radiator running permanently as soon as AC is switched on (either dedicated AC fans or activating some slow speed setting of the actual electric engine cooling fans installed on the radiator) ............. is the W124 not doing something similar?

Is the "overheating or engine temp gauge fluctuation" situation fixed or better if you run without the AC?

IMO the AC high pressure line should never ever reach a point where its spitting refrigerant - AT ALL or EVER!. There is supposed to be a safety pressure cut-out switch that disables the compressor clutch completely if an overpressure condition occurs so this whole thing sounds very strange to me