1988 300ce fan clutch

[hotrodder]

If you're certain the gauge is trustworthy* then yeah, pump makes most sense

* A while back the gauge on mine started misbehaving randomly creeping up or sometimes (more usually) jumping about in a way that's obvious it's the gauge. In either case tapping the thing results in it going to back to normal for a while. Not likely to be the case if your gauge is reliably following a set pattern of hotter at low speed/idle and normal at higher speeds rpm... if locking the box out of 4th, or even restricting it to 1st & 2nd, when pootling around town results in lower temps (when moving) that'd pretty much confirm the pump isn't flowing enough at lower rpm for whatever reason (impeller corroded, erosion of the ally casting messing up clearances etc as you've ruled out wobbly/rough bearings)? Can just about make out the impeller with the 'stat removed and coolant drained but not enough access to check clearances etc, only enough to tell if it's a properly rusty mess

 

[WDB124066]

I haven't read all of this but you are aware the listed thermo is now an 87 where-as the factory fit one was 85. I put in an 83 and it copes much better in the heat than 87, 85 is NLA here..

If it wasn't I was going to look to put one in off a 129, 140 or 210 - they cut in at 92 instead of 96 Deg C.

 

[merc85]

Could it be a Partially blocked heater matrix? do the pipes to and from the matrix get hot?

Impellor on the water my be corroded too.

 

[anfieldassasin]

If you're certain the gauge is trustworthy* then yeah, pump makes most sense

* A while back the gauge on mine started misbehaving randomly creeping up or sometimes (more usually) jumping about in a way that's obvious it's the gauge. In either case tapping the thing results in it going to back to normal for a while. Not likely to be the case if your gauge is reliably following a set pattern of hotter at low speed/idle and normal at higher speeds rpm... if locking the box out of 4th, or even restricting it to 1st & 2nd, when pootling around town results in lower temps (when moving) that'd pretty much confirm the pump isn't flowing enough at lower rpm for whatever reason (impeller corroded, erosion of the ally casting messing up clearances etc as you've ruled out wobbly/rough bearings)? Can just about make out the impeller with the 'stat removed and coolant drained but not enough access to check clearances etc, only enough to tell if it's a properly rusty mess

Pretty sure the guage is good have tested with 2 seperate guages both same behviour. Locking out 4th and higher rpm would be good test will try that. Noticed today temp got a little. Over 100 In standstill and then suddenly came. Down to 85 rapidly by self so that would probably be new fan clutch although oddly it roars for 10 secs from cold but at just over hundred no roaring.

 

[anfieldassasin]

I haven't read all of this but you are aware the listed thermo is now an 87 where-as the factory fit one was 85. I put in an 83 and it copes much better in the heat than 87, 85 is NLA here..

If it wasn't I was going to look to put one in off a 129, 140 or 210 - they cut in at 92 instead of 96 Deg C.

Hi yes, asked mercedes but they could only supply me an 87 thermo. Couldn't find anything lower anywhere else. I had an 87 on my 230ce but it never behaved this way. Maybe M102 to m103 isn't a fair comparison and this is how they run? Just worried if it's doing this in winter what's umber would be like!

 

[anfieldassasin]

Could it be a Partially blocked heater matrix? do the pipes to and from the matrix get hot?

Impellor on the water my be corroded too.

The heater matrix blows out really hot air, at times too much and I have to turn it down. The pipes also get hot evenly all round.

 

[WDB124066]

MB also sell a flushing kit so you can flush your car the way MB recommends. Could be a backflow situation to flush out the big bits...

I have the kit somewhere here.

 

[brucemillar]

I am wondering if you have an air lock now?

You have replaced all the "obvious" suspects.

Can you get the front of the car up higher than the rear (as if on ramps).

> Remove the rad cap.
> Turn the heater and blowers up to the hottest temp.
> Start the car and let it run for an hour with the rad cap off.

That should burp it if there is any air locked.

My thinking here: If it the heater gets hot, then coolant is being pushed into it. If it is getting "too hot" then it is not getting out again in an even flow.

It's a sealed system, so the coolant should flow evenly round in a loop, pushed by the water pump (when the heater is up to max and the stat is open). Any blockage will cause hot spots (as you describe). Air in the matrix will cause an issue.

The other thing, is get a coolant pipe off the matrix and run the engine to see that coolant is flowing (I don' know your car so have no idea how easy/not) that may be.

On my Pajero (issues similar to what you have) I removed the pipes to the matrix and discovered a long piece of old head gasket flapping about in the inlet pipe. Pulled it out and BINGO.

You could also (with the engine running and the rad cap off) look into the rad when the stat is open. You should see coolant being pushed across the rad? That would give you a good indication if the water pump is good. No movement would suggest the pump is goosed.

If looking into the rad? be careful please. If you have an air lock and it burps when you have your eye peering in, that would not be funny for you.

 

[anfieldassasin]

Thanks guys I wondered about air also. Capacity for car is 9.5 litres but it only took 8.5ish going back in. I will see if I can get any air out this weekend.

Another odd thing I noticed was that if I turn the heater to full on it sits at 80ish if I turn everything off including turning the dials to cold the car sat at idle at 85 degrees for 30mins where as before it would have gone to 100 in a few mins. You might be onto something Bruce. Will report back in due course

 

[brucemillar]

It is very difficult to diagnose by checking temps. As stated earlier there are just so many variables. Accuracy of the gauge being just one. Thermostat opening point is another.

From cold and at idle the viscous will normally lock up for a few seconds and that is usually audible as a roar if you blip the throttle. This is normal. After a few minutes the viscous should settle and then not lock up again until it reaches it' designated temp (usually about 98c).

Again from cold you should see the temp gauge rise at idle then fall to "normal" running temp - AFTER - the stat opens. So if the stat opens at 82? The gauge will normally climb to around 90 before dropping back to around 87. These numbers are not exact as your engine may run slightly hotter or cooler, but you get the idea.

The engine then cools dependent on air flow when moving and viscous when standing with the gauge rising and falling slightly. Dash gauges are usually pants and are just to give a clue that things are OK or NOT. The better test is to fit a calibrated gauge or use an infrared thermometer. This allows you to point it a various bits of the system whilst it is in operation and will show hot or cool spots.

With what you have already replaced and air lock is very probable. It only needs a tiny lock to block the flow in the same way a switch or stat would. Getting the front of the car up as high as you can gives the air the best chance to burp with the rad cap off.

 

[WDB124066]

I haven't read all of this but you are aware the listed thermo is now an 87 where-as the factory fit one was 85. I put in an 83 and it copes much better in the heat than 87, 85 is NLA here..

If it wasn't I was going to look to put A FAN CLUTCH in off a 129, 140 or 210 - they cut in at 92 instead of 96 Deg C.

You may want to look at another fan clutch as above if you have no luck elsewhere. I clarified the earlier post.

That with a Mele 83 thermo will make the system behave but won't find the root cause.

Did you ever look at the duo valve, bits of stuff will tend to collect there...

If you have AC you might find with the overheating you have lost a bit of gas - maybe get that refreshed.

 

[hotrodder]

The 'stat sets the min running temp and, as long as there's airflow through the rad, maintains things around that temp by varying the amount of coolant shunted through the rad. One that opens 2 or 5° sooner shouldn't make a significant difference, or if it does it's doing so by fixing symptoms
Same deal with a fan that cuts in at a lower temp and really shouldn't be needed in the UK

You'll never get all of the coolant out when changing it, how much gets left in depends some on the angle the car's sat at when draining it but there'll always be some left in both the rad and various places in the block etc

Air lock is a good glass 1/2 full call, to get the obvious one out of the way the new 'stat was installed correctly (vent hole/jiggle pin/ball valve at the highest point) right? I've got a vague recollection the m103 also has a bleed point on the head somewhere and/or maybe one in the top of the 'stat housing?

If the temp drops at higher speeds then (as it's got a new rad) it's likely related to coolant flow rate. Either a restriction that gets overcome by pressure when the pump is spinning faster (cooling system has already been flushed back on pg1) or the pump isn't as efficient as it should be. To supply enough flow at idle an engine driven pump typically flows more than necessary at higher rpm most of the time...

Cranking the heater up is always gonna lower the coolant temp, albeit limited by the 'stat somewhat because once that's closed there'll be virtually no flow through the main rad. If there was a blockage to/from the heater restricting flow the heater won't be as efficient i.e. the coolant in it is giving up heat to the interior and to keep doing that it needs a constant supply of hot coolant

 

[WDB124066]

An 83 over an 87 makes quite a bit of difference, it doesn't tend to go over 100 ever where as with an 87 it stays above 100 most of the time in traffic and I've replaced everything except for the heater, head and block.

 

[brucemillar]

The other thing to check, is the rad cap itself. It needs to be the correct pressure and preferably OEM. Any tiny blow-by at the cap and you will see odd temp fluctuations. The best way to check this is to replace it as it may not be obvious that it is failing due to the pressure spring and type of seal.

On my Pajero (I know it' not a Merc, but the same principles apply). The hoses to and from the heater matrix are 20m, whereas all other hoses are big radiator sized jobs. As the coolant flows directly from the engine to the heater, then back again this always makes them a weak point for any blockage on the entire system. Either by them collapsing or leaking, or, as in my case getting obstructed by lumps of old head gasket. This led to all sorts of strange cooling/heating behaviours but mainly showed up issues when under load or stuck in traffic. That pointed to the viscous, which I replaced without curing the issue. I also replaced the stat and the rad core, fitted a new aftermarket temp gauge and sender and bought an infra-red thermometer.

 

[anfieldassasin]

Thanks guys, lots of useful info!!

Our landlord is selling our house so money wise all is on pause and I have to work with what I got for now. Bruce expansion tank cap is new and from merc directly, it's the correct pressure also.

The thermo ball valve is pointed at highest point (I checked with a mini spirit level before installing so I knew where to orientate it).

I've flushes the system a few times now including with hose. The interior heat is very good which tells me Duo valve and matrix are good with no blockages.

I took out the new sachs fan clutch yesterday for inspection, since I put it back I noticed it locks up first thing from cold 15 secs or so later unlocks and stops roaring, never hear it roar again after that as engine temp only ever gets whisker above the 100 degree line, when it does it comes down by it self if I don't accelerate or I can induce the temp drop by reving, of course it drops when I drive off.

I bled the head by unscrewing the temp guage sender untill only coolant ran out and re-tightened it. Car was always from draining to filling pointed nose up with Jack and jacks stands.

So thinking logically (correct me if wrong):

No leaks and new reservoir cap so pressure in system. Should be good so don't think it's that

New rad and driving at speeds above 35mph temp holds nicely at 85, if I engage kick down and rev to 4k plus temp drops to 80 or whisker above 80. Fan clutch engages when cold then disengages, So air flow doesn't seem to be an issue (unless fan clutch isn't engaging gradually according to temp rises?)

So that leaves me with circulation? (pump, air lock or debris in system causing blockage). Or alternatively head gasket? ( no mayo anywhere or coolant loss, or bulging pressurised hoses to indicated exhaust gases leaking into cooling system). During all this work I found an oil leak at front of head drivers side above tensioner but can't tell if from CHG or timing cover? (pic attached)

Apologies for the long post

 

[WDB124066]

Did you take an 85 thermo out and replace it with an 87, if so what you are describing above is very consistent with what I get here when I did this. The changes you are seeing between how your system was and how it is now could be due to a 2 - 3 Deg C later fully open temp. Put in an 83 and it will behave better maybe won't go over 100 ever unless you are in very hot weather going up hill slowly in traffic etc.

Fan clutch shouldn't lock up at start, maybe it is not unlocking from the end of the journey before....? Maybe put it away cold to see...

 

[anfieldassasin]

Did you take an 85 thermo out and replace it with an 87, if so what you are describing above is very consistent with what I get here when I did this. The changes you are seeing between how your system was and how it is now could be due to a 2 - 3 Deg C later fully open temp. Put in an 83 and it will behave better maybe won't go over 100 ever unless you are in very hot weather going up hill slowly in traffic etc.

No both stats old and new were 87degrees. Only change since all the work on cooling is that now rather than the car staying at close 100 degrees no matter the speed, it now sits at 85ish above 35/40mph.

Where did you buy the lower temp stat from? Mercedes here in Southend have never even heard of a tropical version, it doesn't come up in thier catalogue and I can't find one online

 

[WDB124066]

home | 4mercs

What exactly is your concern again, I've lost the plot!

 

[anfieldassasin]

home | 4mercs

What exactly is your concern again, I've lost the plot!

Haha, to be honest so have I mate.

Concern I had before was temp reaching 100 degrees at all speeds, and now its that at slow speed below 30-35 the car is reaching 100 degrees and I can feel a miss or slight roughness to the idle.

To be honest if you guys told me I'm worrying about nothing at this point then i'de probably pack it in and see what happens come summer time and worse comes to. Worse swap out water pump then and/or add an electric fan as Bruce suggested.

 

[WDB124066]

Sounds like you are almost there. Hot & Pop idle can be running too lean, get your mixture checked...