940 heater matrix failure

[Laird Scooby]

Originally Posted by 940volvoman

Dave(Mr Laird Scooby) what did you mean when you wrote the coolant caps used to be colour coded, but not any more. My new one was still green,like the original...

Once upon a time, the different colours meant different pressure ratings, now it seems they are all green and you have to read the pressure rating.

As for the question about how it works Shawn, to save myself a lot of typing, here's a link to a Practical Classics tech article that does a fair job of explaining it. Predominantly about a radiator cap, the expansion tank cap is similar.

https://www.practicalclassics.co.uk/...%20if%20fitted.

[griston64]

Grey and green are the same pressure rating. The green was an updated version of grey.

Wasn't really colour coded tbh

Reservoir Cap. [Editor] Symptoms of Failure. Your reservoir cap can fail. Usual symptoms include hot coolant leaking out of the cap or collapsed hoses due to the cap's inability to relieve vacuum in the system when it cools. Replacement Caps. [Dave Stevens] The coolant expansion tank caps used are as follows:

grey = 150 kPa (22 psi) superceded by the green cap
green = 150 kPa (22 psi) standard issue for all 700/900s
white = 100 kPa (15 psi) uncommon
black = 75 kPa (11 psi) standard issue for 140/240s
It's always best to use genuine Volvo or at least a reputable OEM brand. The green caps provide for optimal engine operating conditions in 700/900s. Some people believe the lower pressure (240) black cap doesn't stress the plastic sides and fittings of the rad tank as much, especially in a hot turbo engine compartment and especially as the rad ages. With that thinking in mind I've decided the trade off is worth it and use a black cap in my turbo, but have kept the green cap in my NA. Remember that the higher pressure caps prevent system boilover in high temperatures and allow higher engine operating temperatures, important for good fuel economy.

[Laney760]

Hi to All

Car was rushed in and through for me by my garage to enable me to work in it and not have to keep borrowing my partners car so I am not complaining about their work! I have just emailed them about popping it back to them to be looked over.

So, my new expensive high spec matrix is not putting out as much heat as the awesome previous one, quite disapointed? I wondered if there is an air lock in the system. If I squeeze the big top coolant hose to the rad which is not stiff but not as soft as it used to be to squeeze, then there are bubbles coming up in the header tank? I assume that this means there is an airlock? They did drain and refill the whole system with the correct coolant which I supplied.

[Laird Scooby]

I think your car has AC Ellie so the heater valve will be in the engine bay near the bulkhead and the hose with the heater valve in should go to the lower of the two stubs from the heater matrix that come into the engine bay - have a look to make sure that's correct. If it isn't, you're likely to get more heat from it at idle in traffic than when driving along and would help create an airlock, hence the bubbles.



(Image "borrowed" from https://volvoforums.com/forum/volvo-...s-940-a-66365/ )

Because there is always some air in the system, usually above the level of the coolant in the header tank it's possible to get the odd one or two from the radiator when squeezing the top hose but it should clear over the course of a few days at the most.

[Laney760]

Cheers Dave, I will check although it is disappointing when idling and when moving.