Hey guys,
This is my first post on this forum, but I have been driving and working on Volvos for years now. Im a little stumped on this one so I thought I would see if anyone could help me out.

A few months ago I noticed that my dipstick was a milky, but my car still ran fine. Its a 97 850 non turbo automatic with 246,000 miles. I figure the head gasket was starting to go, but hadnt blown yet so I would just replace it. So I did. I didnt have the head checked because it hadnt overheated, so I figured it wouldnt be warped, and I didnt have the time to do so.

Since I replaced it I took it on a 500 mile trip, it ran fine the whole way and I had no issues whatsoever. The next day I got in my car and noticed that the low coolant light was on, so I refilled it and drove it about 10 miles, no problems. The next day I got in it, same thing, low coolant. I filled the resovoir and started to drive it to work and made it about 10 miles and it started getting hot, so I limped it back home. When I got home I checked the oil, it was clean, but the coolant was low again, it was running smoothly as well. I drove it around a little the next day and when it got hot I turned the car off, let it sit for a minute then turned it back on. The car went to normal operating temp then stayed that way for the rest of the day. The next day I went out to check the oil and the coolant. The oil is milky sludge, and the coolant definitely has oil in it now. It overheats, loses coolant, the heater works off and on, but it still runs smooth.

Im super confused what its doing. I would think if the head gasket was blown the car would run poorly, and if the oil cooler hose had blown the engine wouldnt have coolant in it. Also, after overheating the car cools down and runs at operating temp.... Im dumbfounded so any help would be great. Thanks in advance.

 

Hi and welcome to the forum.

Here lies your problem. If you ever have a head gasket breach with one of these cars, you have to have the head decked. Did you put a straight edge on it?

The only thing that would make the car run poorly is if one of the cylinders is leaking and the car misfires or gets coolant into the cylinder.

My daughter drove her S70 GLT for over a year with a bad head gasket. It was leaking combustion gases into the coolant chamber.

There is also a chance that you have a bad radiator. It can mix fluids as well. You may be able to pressure test the radiator to see if it holds pressure.

 

The non turbos have no oil cooler so the possibility of mixing in the radiator drops out.
The had can get warped when you take off the head or put it back on if you are not taking care in which order the bolts have to be loosened / tightened.

Do a compression test and see what it says. It is also possible to analyse the exhaust gases and see if there are traces of coolant in it.

 

My guess is the compression will be good, that's why it's not misfiring. When our S70 had a bad head the compression was good across all cylinders.

I guess he could also have a cracked block. I would pull the head and check the head for flatness first. If it's flat either the block is bad or the head wasn't torqued down properly.

 

Thanks for responding guys. I really didn't check the head at all. I know better, but I was out of town and was under the gun to get it back together and get home. Stupid, I know.

So I will pull the head again and check it for flatness. I know its game over for the motor if the block is cracked, and without having any real way to check, how probable is a cracked block on an 850?

 

"the heater works off and on, but it still runs smooth."

For the oil and coolant to mix it pretty much needs to be a head gasket as a cracked block, at least any cracked block or head I've seen doesn't allow for the kind of intermixing you describe.

The part about the heater is a classic head gasket as it's pumping air into the cooling system and the heater core will get air locked. If it's low on coolant and you lose the heater you are very low and it doesn't come back and that's when you need to shut it off, no coolant flow. If you have enough coolant for flow then the heater core will fill with air and purge so you get intermittent heat.
That nursing it home is what worries me.

I understand you did it away from home and you were in a hurry but did you follow the sequence releasing the torque on the head and then again when replacing and reinstalling ??