1995 Volvo Heater Control Valve Failure...Advice?

Las940 · Post by **Las940** » 21 Jul 2014, 21:06

Hello,

1995 Volvo 940 Sedan (non-Turbo) 142,000 miles.

I was idling in traffic today when I see white steam expelling from under the hood. The engine was not overheating, although the cooling fan was engaged. I quickly pulled over for further inspection.

Turns out the nipple of the heater control valve was disintegrated. All coolant lost.

For a temporary fix, I capped the hose coming from the engine with a bolt, some gasket sealer, a rubber cap, and a hose clamp. The sealant is supposed to take 12-24 hours to cure.

My question is, could there be a cause for this, other than a failed nipple at the heater core valve? Bad water pump? Leaking head gasket? I have seen no white smoke from the tailpipe... Also, is there another way to remedy the situation? I live in Hawaii, so heat is not necessary. Could I bypass the heater core, and if so, could someone please explain (or direct me to a tutorial) how this is done?

Any help would be appreciated. Thanks.

93Regina · Post by **93Regina** » 21 Jul 2014, 22:51

Las940 wrote:1995 Volvo 940 Sedan (non-Turbo) 142,000 miles....bypass the heater core

1. After coolant is added, start engine, and have you/someone place full hand over coolant-refill tank (with lid off). Increase RPM to 2,000 RPM...does person feel pressure at refill tank.

2. By-pass - I'd have to see how yours is setup, but one hose going to heater control valve is joined with other hose coming out of cabin heater-core. From an auto supply, one gets a barbed fitting to join these hoses, with clamps.

Cabin Heater Core - If it is good, one does not yank hoses off of it. Normally, I take a knife to them, and then gently take them off. One can try to gently twist them.

Las940 · Post by **Las940** » 21 Jul 2014, 23:17

93Regina, thanks for explaining the bypass process simply. This had crossed my mind, as it seems like not only the cheapest, but also the easiest solution.

My setup is such as that there is one hose coming from the engine block (which is now capped), to the heater control valve, and then one hose from the heater control valve to the firewall.

The clerk at the auto supply also suggested I could "plug" the hole in the engine block that is currently still fitted with the capped hose I mentioned. Difficult access poses a problem though...

93Regina · Post by **93Regina** » 22 Jul 2014, 06:57

Las940 wrote:The clerk at the auto supply

Different strokes, different folks; I've used "pass thru" method, but like a control valve does, it can be blocked.

Head Gasket - When engine is cold, do that test in item one above; if there is pressure at coolant-refill tank, there is an issue to deal with.

lummert · Post by **lummert** » 22 Jul 2014, 07:03

I'd suggest that it's better for the engine's cooling system if the valve is bypassed. It can be restricted, but stopping flow completely may effect cylinder head cooling.

Las940 · Post by **Las940** » 27 Jul 2014, 21:36

Good news -- I was able to successfully bypass the heater control valve by installing a piece of 5/8" plastic tubing between both hoses. No leaks (yet), and engine seems to be operating at normal temperature.

However, I do have one question. What should I do with the small vacuum line? Should I simply let it alone and ignore the hissing sound it makes? Or should I plug it? Does anyone know if there are any negative repercussions from either scenario? I just want to make sure before I begin driving it again.

Once again, thanks to everyone for your help. Volvo should be back on the road in no time.

93Regina · Post by **93Regina** » 28 Jul 2014, 06:58

Las940 wrote:small vacuum line?

Plug it off....