260e 124 series, overheating

[emimec]

Above post was very helpful, thanks. I've linked a wire with a bulb to the auxiliary pump, that reaches inside the car, so I should in theory be able to get an indication of when the pump works,

 

[emimec]

part resolved

Having monitored coolant level and temperature level for around a week, it seems the causes were.

1.Faulty rad top elbow that feeds expansion tank via a small bore hose.

2. Faulty hose clips, despite feeling tight, 2 had damaged threads preventing full tightening.

3. Water loss from auxiliary pump.

4. New thermostat fitted, but tests on old one did prove it was working.


Temperature and coolant levels have been constant for a week, average 85c.

Despite connecting a wire and bulb to the auxiliary pump connector, at no time has the bulb lit, and I have tried countless heater and air con combinations. So further investigation is needed to see why the pump earth does not activate. Only possibility at the moment could be due to weather not cold enough.
Bob

 

[emimec]

Forgot to say new rad was fitted.

 

[optimusprime]

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.

brown is negative on this model.

 

[optimusprime]

News

Let us know how you get on with the car.

 

[emimec]

I will check next week to see if the duo valve earth is apparent, then check between said valve and aux pump earth, to see if they are linked. Failing success, i will remove heater and air con panel in cockpit and see if the problem is there.

 

[krimat2005]

right, so to help you out a bit: duo valve and heater pump live is constant. negative is dependant on temp.settings, ie if you need warm air inside then duo valves opens up and pump starts to run. if desired temp is reached (sensor is by rear view mirror) then negative is switched off, so no heating/pump. then air blown into cabin gets cooler as long as no warm is required, depending two round temp switches. try turning both temp controlers to red/max temp, this should give you negative at duo valve/pump. let us know.

 

[emimec]

Removed heater control panel from cockpit.
Now, I have 2 spare ones of these, part numbers are identical to all 3.
First observation is on my car one, pin 4 is missing from the socket on the heater panel socket, and it's mated to a Brown / green stripe wire on the harness plug. A quick substitution with one of my spares, Both of which have pin 4 in place, made no difference to the pump or earth function.
Second observation is the 3 button air con control seems to be a bodged job. The switch is held in by some thick black grunge between the pcb and back of switch.
I will need to desolder the cables to free the switch from the housing. Would like to replace the switch if I can find one.

 

[emimec]

Forgot to test earth from duo valve again, do tomorrow.

 

[coalville126]

Second observation is the 3 button air con control seems to be a bodged job. The switch is held in by some thick black grunge between the pcb and back of switch.

It is a sign that it has been retro-fitted after the car left the factory. It might have been done by the dealer prior to delivery or even a later date, but dependent on the install, I wouldn't call that a sign of a bodge as retro-fitted units can give years of trouble free service. My parents had such a system by Diavia fitted to a 300E upon purchase at 3 years old from a main dealer. It gave no trouble over the next 6 years / 100k miles.

 

[emimec]

I think your right, No problems with air con overall, just the push button switch mounting fixing doesn't look as professional as one would expect for a mercedes. The button assembly should ideally be a snap fit to the plastic base plate, but my one is gooed in position and the cover for the whole unit has been cut to accommodate said switch, whereas one would expect a purpose made cover plate.

 

[emimec]

Tested duo valve connectors using a wire with a bulb soldered the other end. Lights comes on Only when the air con buttons are pressed and I noted the top button for defrost only works if part pressed, push it fully home and bulb goes out, so faulty top button. After this test, I then transferred my wire to the aux pump plug, No combination of button pushing Lights bulb. This is with my original heater Temperature and speed panel still in place, with the missing pin 4. So will try again tomorrow with substitute panel if I can .

 

[emimec]

Forgot to add, sounds like a relay connects behind air con buttons when air con buttons are pressed ?

 

[emimec]

Having monitored the water temperature and any coolant loss over the last few weeks, it has been interesting. On two occasions, and after a short run, then a second short run, there has been water cooling out of the over flow behind the front wheel, could be due to over filling on my part. Also noted a bubbling round again in the area of the two differential valves situated behind the fuse box.
Beginning to think head gasket now, despite it was done professionally some time ago. Also noticed engine seems to shudder at idle a bit more than it did time ago, not a smooth idle, vibration when in drive position.

 

[carat 3.6]

A compression test will confirm it.

 

[optimusprime]

Keep us members informed please .

 

[GadgetBoy]

In any diagnostic procedure never ever discount something because it's new or was recently fixed.

The new or fixed components are no less likely to have failed than the existing components.

 

[emimec]

I shall be somewhat upset if it does turn out to be the head gasket. Cost over a grand last time as I had the valves and seats renewed, radiator pressure tested and cleaned. Even bought genuine mercedes gaskets to be sure all was as it should be. Garage was also a mercedes specialists, the owner of which I know well who has looked after many 260e for me, including the worst scenario, heater matrix replacement on a previous car.
Bob

 

[stwat]

It could be something as simple as needing a new header tank cap.

 

[emimec]

Short trip today, 10 miles each way, no problems with temperature during trip.
Stopped off at local shop for five minutes to get a snack before returning to my workshop, and could see water leaking from the overflow pipe behind front wheel. Returned to workshops, less than half a mile, and line of water on road where I manoeuvred into parking space. Left engine to cool, removed cap and ran engine, constant bubbling and water from header tank. Left to cool again, topped up with engine running, and removed bleed bolt from stat housing, all ok in header tank when filled. See what happens tomorrow as I have an 80 mile round trip to do.
Not had time to get a compression test done yet.