Heater control valve, 1994 940 Turbo
 

Hello forum,

I have some maintenance responsibilities on a '94 Volvo 940 Turbo, and I had an event that I hear is not that uncommon on these cars. The heater hose burst and the car needed a top-end job as a result (head gasket, head machining, valve job).

Putting the finishing touches on the job, the heater control valve finally broke after leaking
a bit. The plastic body cracked and the plastic pipe came off entirely. I think it was original. Half metal, half plastic.

It happened in a gas station, so I MacGyvered the replacement of the valve for now with a 13mm deep socket working as a pipe! It leaves a gap in my tool box but keeps the system from leaking and the heater working.

But for future replacement, I hear people recommend a motorcraft part, which is half metal, half plastic like the original.

I was wondering if I could use Four Seasons 74603 instead. Can anyone see any downsides with this? 74603 is an all metal unit. It is a replacement unit for early 1970s Buicks, Oldsmobiles, Cadillacs, etc. It seems safer than a half plastic unit, and I have seen the damage that can happen from having one of these fail. On my old Cadillacs, I have never seen one of these develop a water leak (although I have seen them develop bad vacuum leaks after 40+ years, but I'm not sure we care as much about that).

https://www.rockauto.com/en/parts/fo...ter+valve,6860

I should add that it's an A/C car (A/C doesn't work but still), so the control valve is on the engine side of the firewall.

Try a Four Seasons 74803 instead - cheaper and more closely matches the original :

https://www.amazon.com/dp/B000C2Q92Y..._t2_B000C2Q8VG

Under 10 bucks so not a bank breaker if it fails again and won't rust out! As long as the vacuum causes the valve to shut to replicate the original action you'll be fine. You can check this by starting the car, putting the temperature on coldest and fitting the vacuum hose to the stub on the new valve - you could even make a hole in the bag just big enough to do this so that if for whatever reason it works the other way round, you can send it back in its original packaging for a refund.

Should be a clear plastic bag it comes in (hopefully) so you should be able to see the action by holding it up to the light. No vacuum allows the valve to open so if you're doing a coolant change, it automatically fills/flushes the heater matrix and vacuum closes it so you can shut off the heat for cold air coming in.

Like the ideea of a deep 13mm socket - excellent redneck engineering! :tounge_smile:
Here in the UK, domestic copper water pipe comes in 15mm and 22m sizes, the 15mm stuff is ideal for heater bypass emergencies! :thumbs_up:

I found a valve on ebay from Australia last year that looks remarkably similar to the Volvo original and is cheap. Even with shipping it is less than a Skandix copy I bought a few years ago.
Might be worth a punt: https://www.ebay.co.uk/itm/Heater-Va...53.m1438.l2649

Your experience of unnoticed coolant loss is a good reason to fit a coolant level warning lamp, which is easier than you might think: https://www.volvoforums.org.uk/showthread.php?t=66295
This has saved my engine more than once, especially when my heater control valve snapped in half, dumping the coolant on the driveway. Having a warning lamp allows you to stop the car before major damage occours. Note the lamp to the right of the ABS lamp in the below pic.

https://live.staticflickr.com/65535/...78c2b9df_b.jpg

They appear to ship to the USA as well, not much in it cost-wise though.

Better still, going back to the supplier the OP originally quoted, Rock Auto do another Four Seasons valve even cheaper than the one i found on USA Amazon and it's designed for the 940 as well :

https://www.rockauto.com/en/moreinfo...289088&jsn=399

Price is only coming up in GBP as that's what Rock Auto is set to in my preferences so i don't have to keep trying to convert to £ from $ but it's about £6.50 so probaly about $8 ish.

I might be wrong but i thought US spec 940s had a low coolant light as standard? :thinking:

Thanks everyone for all the suggestions! Especially that low coolant lamp, that sounds like worth doing.

Yes I am in the U.S. but the car is actually in... Sweden...! So it is a left-hand drive euro-spec car.

So the reason I was thinking of getting the valve for the old GM land yachts instead of something that's a more direct fit is specifically that the GM valve is all metal rather than all plastic or mixed. I was thinking the all-metal valve is unlikely to come apart suddenly and catastrophically the way I am apparently not the only person to have suffered. Mine came right apart in the plastic section, which would have led to another top-end job if it happened on its own (and it was close to going, it was leaking from a crack in the plastic already).

Of course a low coolant lamp is an even better idea, the heater valve is not the only thing that can fail (in my case it was one of the three heater hoses...)

Great forum!! Thank you!

Coolant level sensor and heater valve.
 

I'm just in the process of doing a coolant level sensor. I got two sensors from a breakers yard (one off an early 960- I took the crusty tank as well, and one off a V70- looks like same sensor just different plugs). I'm going to wire it in place of the windscreen washer empty sensor- I don't need to know if screenwash level is low, whereas engine coolant...
It would be nice to get a buzzer in there somehow, even wire it up to the unimportant car alarm horn!
I bought a new expansion tank last year, I can't remember if it had a float, possibly not. There is a part number on the base of the crusty 960 tank, which does have a internal float, I may have to order one of these.
I did the heater valve earlier as preventative work, using the half metal, half plastic motorcraft valve. Fairly similar to the one that came out, apart from vacuum nipple. If I'd known of your all metal one I'd have gone for that. Fit and forget?
Previously, on three 940's. I've had failures on:
Three radiators.
Two expansion Tanks.
One heater hose.
Two heater valves.
One expansion tank top hose (the thin one to the rad).
Probably some other hoses.
Two water pumps.
The engines all, amazingly, survived, without obvious damage. I think I was lucky?
Good at sensing steam?
My present 940 came to me with a slight external leak from cylinder one, I didn't spot it at the point of purchase. I ran it for a while then did the head gasket recently, an odd choice of birthday present I suppose! And all my cooling hoses and parts are now young, unlike me ...