hi,

at last I replaced the expansion tank with a new one. We'll see if it solves the problem.
I 'll keep you informed.

just for the record, it is possible to test both fan speed using the diagnostic mode A6. I put the plug in the A6 socket, push 3 times (?) the button, and the inboard computer ...

hi again,
so I received the new cap, and this did not solve the problem.

Today, while further debugging this issue, I noticed the following :
the car was iddling since15+ mins, and the coolant overflew. The fan kicked in, and I could see the coolant level drop rapidly (10 sec) to a normal level ...

I ordered a new cap.

ok I did check :
the cap seems ok, I don't see any crack
I don't see any heater leak
I checked the coolant level as per the video. When the car is hot, the level increases by like 5mm. It seems ok.

I have taken the expansion tank out of its support bracket, and see cracks at the bottom (see the ...

thank you for your replies, and for the video link. Robert, I am using your videos a lot, and find them very useful, like the pcv one.

So I will recheck the cap, and see how I can get a new one.
I'll also check the coolant level, as in the video.
I haven't noticed any leak at the heater core, but ...

thank you for your quick reply Mike

The cap is the green one, 20 years old. Do you suggest to change it ?
If there a pressure leak , then shouldn't it be boiling any time ? also when the car is running ?

Hi list,
I hope to get ideas on how to debug this boiling coolant problem.

Symptoms :
since some time ago, the car is consuming coolant. I noticed traces of coolant at the coolant tank cap. One day I noticed the coolant was boiling in the expansion tank, while the car had just been shut down. But ...

the answer is here :
http://volvoforums.com/forum/volvo-850- ... tch-79119/

Hi list,
I would like to have advices on the possible failure on my HPS, before buying this costly part. This is the story :

I am in the process of fixing my A/C that I didn't used for years.
Before testing the system for leaks, I am checking the electrical part of it.
I noticed that my ...