Air locks? W126 M103

[stwat]

I flushed the coolant system and fitted a new thermostat along with fresh antifreeze coolant today.

The problem I now have is that it is now running too hot. It can't be air in the matrix as the heater has never been so hot. I'm talking melt your eyeballs hot

But the temp gauge rises up to 100 deg when stood and only drops down to about 85 to 90 deg when driving. I have had the car pointed up hill with the cap off revving the nuts off it to try and clear out any trapped air but to no avail

The main reason I changed the thermostat is because it was running to cool. It's the bloody other way round now

Any ideas?

Ta.

Stu

 

[grober]

Wrong /faulty thermostat opening too late? Could even be the wrong one in the right box? Where there any markings on the one you put in? Who made it? etc ---- could be you have just been unlucky and got a duff one? Sometimes when you drain a rad if there are lot of suspended "solids" they can settle out in the radiator -solidify and block some of the passages- especially if the radiator sits " dry" for a time ----this can be terminal but usually removed with back flushing the rad.

 

[stwat]

It is a Febi Bilstein thermostat rated at 87 deg, I made sure to check the markings on it before fitting.

I gave the block and rad a good flush and back flush until nice clean water was flowing through each.

I shall leave it parked pointing up hill overnight to see if any trapped air makes it's way to the header tank.

 

[grober]

I was pretty sure you would have done all those but had to ask. The only thing that has changed then is the thermostat and by a process of elimination it must be faulty? A pessimist might venture that changing the coolant has precipitated a CHG failure?--- its happened to me. but hopefully not in this case. That scenario is more likely if the engine has been run for years without much corrosion inhibitors/weak antifreeze mix. new antifreeze is the last straw

 

[stwat]

Well the stuff that came out when I flushed was very brown and took quite a while to run clean

The service book shows the car has had fairly regular brake fluid changes but no stamps at all for coolant changes Oh and the old thermostat was an original MB one, probably in there from day one!!!!

Oh lordy dont let it be the head gasket

Edit!! I was looking at the wrong service book! DOH! The last coolant change(stamped in the book) was in 1994 at 35.000 miles. so it's potentially done another 30.000 miles on the same fluid and thermostat !

 

[grober]

I guess the first thing I would try would be another thermostat or dare I say it-- the old one back temporarily?? If that does no good you have to look elsewhere for the problem.

 

[stwat]

Thanks grober, I'l do that tomorrow.

Stu

 

[jkeith]

The highest point of the cooling system is the header tank and it fills the system from the bottom of the radiator. When you filled the system with the new fluid, did you have the 2 heater contrls set to maximum and was the car level?

Air locks don't seem to fit with the characteristics you describe but I'm puzzled to find another explanation.

 

[stwat]

The highest point of the cooling system is the header tank and it fills the system from the bottom of the radiator. When you filled the system with the new fluid, did you have the 2 heater contrls set to maximum and was the car level?

Air locks don't seem to fit with the characteristics you describe but I'm puzzled to find another explanation.

Yes heater controls to maximum. The car was pointing down the drive But I did try bleeding it with the car pointing up the drive.

 

[stwat]

Panic over. Old thermostat refitted and normal service is resumed. In fact it's better than it was previously. It now sits at around 85 and never climbs any higher and only slightly drops when coasting downhill. Beforehand it would drop off to around 60 when coasting.

 

[stwat]

Just tested the new thermostat in a pan. It only starts to open once the water almost reaches boiling point. So obviously faulty.

 

[jkeith]

Well done Stu, I can feel your relief from here.

I bought my smoke silver 300 se a short while before you aquired yours. I've had the cylinder head gasket done but it's going back into the garage on friday to get a water leak cured. A new water pump should not have been required but I'm hoping the garage will admit some liability.

Like you, I'm tidying mine up and I would like to get the engine bay close to show standard. Painting the exhaust manifolds is also on my list, not sure if white is the right colour, I've seen silver on an W107 300SL but it isn't to my liking either.

The car is awesome and I will get it as good as I can without it becoming a money pit.

Nice to see your progress as a comparison, the engine bay on yours looks much better since you cleaned it.

 

[126-valeter]

im thinking of painting my manifolds as well what the best high temp paint to do this and is black or silver the ebst to do this in on a w126 300se