Behr brand thermostat for 2.7 CRD

[Adrian D]

One good check to see if there's no combustion pressure inside the cooling system is to check for pressure after it sits overnight. There should be no pressure in the system, even a slight vacuum, as per the Sprinter owners/mechanics.

[drover]

Normal for the header tank to let flow into the recovery tank then it will suck it back when cool, recovery tank does need some coolant in it though...............
If the brew of coolant has been watered down it can run at a higher temp also if the by pass on the thermostat is blocked you won't be getting flow back into the system once the main valve shuts, which would show as tank overfull, it could also cause a air bubble to form, the hose from header tank could be restricting flow as well, an internal split wouldn't be noticed. You would certainly know if oil from anywhere is in the system, grey sludge also if head leaking gas it will change colour as well....

[JeanLuke]

Originally Posted by drover

Normal for the header tank to let flow into the recovery tank then it will suck it back when cool, recovery tank does need some coolant in it though...............

Agreed. My problem was that I did not know about the recovery tank. In the CRD is is very well hidden down under the right headlight and beneath the airbox. I thought the overflow from the header tank went to ground. It doesn't.

Originally Posted by drover

If the brew of coolant has been watered down it can run at a higher temp ...

I'm going to correct you there. Ethylene glycol has a specific heat of about half that of water. It is if the brew is too strong (as in too much glycol) that it will run hotter. This is corroborated by the factory service manual.

EDIT: Since emptying the recovery tank my mysterious refilling has stopped.

[drover]

I was meaning if your coolant mix has been diluted with too much water things will boil earlier as the boiling point will be lower and too much just as bad, a 50/50 seems to be the best mix in regards to keeping the temp nice and not eating the insides away.... I used Nulon green HOAT in my WG and its specs for 50/50 mix gives a boiling point of somewhere around 125c, the HOAT in the WK2 is Red and about the same boiling point...

I'm trying to recall if I knew about the overflow tank myself, I honestly can't remember, funny that the WK2 doesn't in fact we have to extend the pipe as it dumps onto a junction and can short things out, cost saving ???

Glad its working better now, unless the temps go thru the roof I wouldn't worry, not all thermostats even the same brand will have the same flow rate..