260e 124 series, overheating

[optimusprime]

did you have the ingnition on.

 

[emimec]

Yes, and engine running. Also tried all sorts of combinations with heater controls and air con. Pump didn't run at all.

 

[hotrodder]

The more I think about this, I think the problem is basically water loss from the auxiliary pump, this then let's the engine overheat in traffic is insufficient coolant, don't recall any warning lights though.

Obviously if the aux pump is leaking it needs fixing but loss of a little coolant won't result in overheating unless the leak is bad enough/ignored for long enough for the header tank to end up empty. If there's coolant in the header tank (even if the level is low) there's enough coolant in the system for things to work properly i.e. the header tank is sited higher than the top of the radiator and there's a small hose that bleeds a little coolant (and any air) from the top of the rad (or thermostat housing) while the bottom of the header tank feeds into the bottom of rad via a larger diameter hose

As said the viscous fan won't lock up until 96-104°C. http://www.w124performance.com/service/w124CD1/Program/Engine/104/20-0020.pdf covers other switching points in the cooling system.
Rather than sticking things into the fan to see if it's locking up personally i prefer just feeling it's resistance with the engine switched off- the difference in resistance to turning by hand between 'freewheeling' and 'engaged' is very obvious when it's working properly as is the noise the thing makes due to the amount of air it shifts

After a proper drive to get the thing properly upto temp how quickly does the coolant temp rise when left idling/stuck in traffic? With the ambient temps we currently have it'd take one hell of a traffic jam (beyond normal sarf London rush hour) for mine to get hot enough for the fan to cut in. 20+ mins queuing for lights on the A20 and the temp gauge would've risen from it's usual 85ish to 95ish, maybe closer to the line that represents 100°C. Similar conditions on a hot summers day and the gauge might nudge past 100 and the fan cut in and stabilise things until traffic starts moving again
Before i changed the waterpump some years back temps would rise quickly when stuck in traffic, even a short stop at traffic lights after say leaving a motorway would see the gauge start climbing pretty much immediately. This is because the tired* waterpump simply wasn't working efficiently at idle. Normal running temps when hammering along a motorway because in order for the waterpump to have sufficient flow for idle/low rpm with heavy loads it flows more coolant than needed at higher rpm...

* in my case it was the pump bearings giving up after 20 odd years and 180k odd miles. The extra play messed with the impellers efficiency and also resulted in a coolant leak from the pump. While the engine was much more reliant on it's fans (including the leccy ones in front of the rad) it still didn't overheat despite me not getting around to changing the pump until the leak was properly noticable i.e. getting a low coolant warning lamp fairly regularly

 

[emimec]

Your right, mine will take a long time at idle to get past 80, however, im convinced now my problem is water loss. The obvious fear is heater rad, been there before, cost a fortune on previous 260e. Checked under drivers carpet, all ok, not done passenger side yet as full of junk in that area.
Drips from auxiliary pump are steady when engine cold, and rad cap off, nothing when hot.
There are no obvious leaks anywhere that I can see. Again, however, after about two weeks, bubbling sounds and overflow from header tank become apparent. Takes about 3 pints to top up, header empty. Temperature will go nearly to red. After top up, on a run, car is under 80

 

[optimusprime]

Water

As i dont know if this as been mentioned before .Look to the rear of engine rh/side , here you can see a pipe coming out of the head , with a hose on it .Now put your hand around the back of the engine in the area that cylinder head is fixed to the block .Now do you see ,or do you feel any water in that area...Another thing i found is that the auxiliary water pump as power from the duo valve ,so check conections on there also.

 

[djf01]

I noticed water loss, and bubbling noises near the brake master cylinder, then on another occasion, Brown water marks over the expansion tank. Also, water coming out the overflow by front wheel.

On my E280 w124 there is the expansion tank in the engine bay linked by a pipe from the top near the cap to an overflow tank in the drivers side wheel well. If you have the same set up it sounds like that pipe is where you have the leak from your earlier description.

See this thread...

Over flow tank - Mercedes-Benz Forum

 

[emimec]

Oh dear, major problem now.
Sat in traffic this afternoon for half hour due to accident at the lights. My car went to the red, then a bang, engine stopped, water loss from car. Seems radiator has now split, so waiting for breakdown truck to arrive

 

[trapperjohn]

Hope they get to you quick before you over heat too.

 

[carat 3.6]

Sorry to say it, but reading through the post's in this thread you have confirmed a leaking head gasket in my opinion.

 

[emimec]

Head gasket was done professionally a few years back. Genuine mercedes gaskets, I bought them.
What I don't understand, is why rad blew and not the filler cap. Car starts and runs seemingly ok now it's cooled down, only ran it enough to park in place from delivery by breakdown truck.

 

[emimec]

I will look tomorrow at the oil condition.
Ironically, I have 2 spare radiators, both came from the same model car, but have a feeling they are different to the one on my car, look smaller, maybe because this car has air con ?

 

[hotrodder]

Yeah, rad core sizes differ with or without aircon. With A/C the rad core is longer and taller but also a bit thinner as space is at a premium due to the condensor. Look up any aftermarket sources and you usually get drawings and core dimensions. IIRC the same two rads are used on the 260, 300, 300-24 and 280/320

What I don't understand, is why rad blew and not the filler cap.

Because the rad was knackered and finally gave up? Water expands by a factor of around 1600 when it changes state into steam...
Dunno about mass produced ally/plastic rads with crimped tanks but FWIW like many others when i fabricate or repair a radiator etc i hydraulically test it at 1.5 - 2 x it's max working pressure

 

[emimec]

Thanks, on that basis, subject to measuring, sounds like I will be having my spare two rads up for grabs !

 

[carat 3.6]

Head gasket was done professionally a few years back. Genuine mercedes gaskets, I bought them.
What I don't understand, is why rad blew and not the filler cap. Car starts and runs seemingly ok now it's cooled down, only ran it enough to park in place from delivery by breakdown truck.

Genuine gasket or not you still need to test it's condition, overheating an engine with a alloy cylinder head can lead to warping and a blowing head gasket.

You've said in post 3 that you've had bubbling noise's by the brake master cylinder, brown water marks over the expansion tank, and water coming out of the overflow pipe. Those are examples of water being forced out of the system under pressure, not a leak somewhere else. I'd wager the head gasket is blowing into a water way, pressuring the cooling system. You don't see any oil contamination because the oil ways are intact.

Warm the engine up and do a compression test, then you'll know for sure.

I will look tomorrow at the oil condition.
Ironically, I have 2 spare radiators, both came from the same model car, but have a feeling they are different to the one on my car, look smaller, maybe because this car has air con ?

If your car has air con fitted, the electric fans are wired to cut in when the engine starts to overheat. Try and see if they are working.

 

[emimec]

Today's discoveries, update.
Changed aux pump with my spare one, original pump had was the type with square holes. Tested both with direct 12v, both worked.
Tested power to pump on car, live apparent, but seems earth wire is dead when using meter set on ohms and connecting between plug and car body and engine. To prove a point, added wire from earth to motor, and it ran.

Second discovery was on old rad, on the right top side is a small plastic elbow fitted with a pipe that goes to water expansion bottle. My plastic elbow was held into the rad with a cable tie, this must have been a problem before my ownership, as I found the past that goes into the rad was broken, so not a good real there. Also, water hose on top in same area had faulty clip, whilst it wouldn't tighten any more, it wasn't really as tight as it could be, the clip must have damaged threads.

New rad fitted, and new thermostat, old stat tested and worked.

Car at idle went to around 85, drive round in warm weather and heavy traffic saw temp rise to just over 100, but dropped when traffic eased and could get more of a run.

I'll monitor this over the next week for coolant lose, of temperature problems.

 

[emimec]

Poor grammar is the fault of predictive text on mobile phone and failure of me to proof read before posting. Apologies.

 

[stwat]

Poor grammar is the fault of predictive text on mobile phone and failure of me to proof read before posting. Apologies.

Know need to opologise. I hate the grammer police with a vengense,,,

 

[Benzowner]

should read everything oops.

 

[emimec]

The main issue at the moment is positive identity of what and when the auxiliary pump is made to run. I feel it runs all the time. But logically, it would soon wear out, so I now wonder if some relay or sender, works on temperature or load to signal pump to run. This could answer why the earth in the pump plug is dead when I tested it, but may be in circuit when signalled to run, assuming it's not a broken wire. So I need to find out where that cable comes from, and it looks like, as mentioned in previous posts, from the duo valve, which works on my car, put plug on to valve with ignition on, and you hear it click. Anyone got a diagram link please ?

 

[millo777]

Maybe this will help shed some light

Aux Coolant Pump Question - Mercedes-Benz Forum