940 Coolant Disappearing
 

I have a 1994 940 wagon which I just worked on for a coolant leak. The hose from the reservoir was bad, so I fixed it. Also, the heater control valve was leaking. I bypassed that because the parts stores were all closed. I figured to replace it in a couple of weeks when it is more convenient. Anyway, my daughter has the car out of town and she says that the coolant is disappearing (1-2 gallons per day). There is nothing under the car, but the interior smells slightly of coolant. Where might that much coolant be going?

Normally that would mean a failing heater core, the coolant leaking inside the car thus the smell, loss, etc, even though 1-2 gallons per day is a lot of coolant...

But you say you "bypassed the valve", how did you do that, straight pipe or bypassing the core itself? If the coolant is still circulating though the core, then, yes leak in the core.

But I have the feeling that with all this leaking history and multiple drivers, someone at some point overheated the thing causing some head gasket damage. One-two gallons a day is just too much loss to account for just heater core leak.

indeed, 1-2G is a LOT of coolant a day. you'd see that dribbling out the bottom of the car while its idling, or major steam coming out the tail pipe, or the front carpets would be very soggy.

If you smell it inside it's the heater core. I had mine done a few months ago on our 89 740. I wouldn't do it myself so I took it to a Volvo experienced mechanic. Just so you are ready it will cost around $1000 from an independant and a few hundred more from a dealer.

As these cars age and the prices come done to practically nothing there will be hard to put this kind of money into them--more and more Volvos are running around with bypassed cores...

my 740 is worth more to me than its cash resale value.

by passed mine as well....and yes my Volvo IS worth more to me than it's cash value.

No argument there... I think a nice, older, well maintained Volvo (and many other European cars) are way more valuable than their market value... My point is that the average driver looking for a cheap way to get to point B often chooses a Volvo just because it is the cheapest car he can find and in that unfortunate scenario the car gets flogged to the death and it's not about to get a $1,000 dollars invested in it, whether it's the engine or much less the heater... And I get real turned off when I see a bypassed heater core.

admittedly, replacing a heater core on some of these cars is a major pain. my son managed to replace the core on his 940SE (960 turbo for all practical purposes), and had to tear out half the dashboard.

heat is more important than AC to me, without it, there's no way to defrost your windshield making driving on cool damp mornings impossible. our 240 hasn't had functional AC in 15 years and when I replaced the radiator, I didn't even bother to replace the AC condensor, I ripped out the hoses... been meaning to remove the dryer too, as its all DOA... kinda wish it was easier to remove the compressor too, but there's no kit for bypassing it on an 87, so the compressor sits there acting as an idler pulley for the PS pump.

I removed the heater valve and connected the two hoses together. It turns out that there was a leak in one of the heater core hoses that was leaking out by the time the car was parked.

Funny I did the opposite a few years back. We bought our 740 new in 89 for my wife. Her 1st new car. She won't give it up so when it breaks I fix it. We blew the condenser a few years back so I replaced all of the hoses , the condenser and the compressor. Converted to 134 and it blows ice cold. We are not in a hot/hot part of the country but we get 80/90/100* days so she needs the AC. I now have to do strut tubes and ball joints. 333,000 miles on OEM.

Ouch! Bypassed the valve, not the core. Hopefully it wasn't overheated enough to damage the motor.

I'm pretty sure he meant he bypassed the valve AND core, otherwise just bypassing the valve would leave the heater on 100% full time.

when my kid's 940SE blew, he used the heater valve AS the bypass splice connector, connecting both hoses from the engine to it, and then refilled the radiator with water he got from a creek. this happened up on a national forest fire road above the snow line, hahahaha, crazy college kids in a station wagon.

https://lh3.googleusercontent.com/-H...y+pt+1+037.jpg
(different trip)

kinda sad, he let that 940SE go as it had several things going south, and he didn't like the 18 MPG it got. I was ready to scrap it, then I managed to fix the various things (biggest one was that the tranny was misbehaving, turned out to be the transmission throttle control cable (oftne called kickdown cable) was misrouted and hanging up, causing bad shifting, we thought the whole transmission was on its way out, so I was able to sell it to another college kid for $2500.