Greetings,

I have a problem with a 1998 S70 T5. I thought I had a bad thermostat because it would go for miles, or even several days and the temperature gauge would stay steady, right in the middle of its range. Then quickly the gauge would go up and the engine would overheat. After sitting a while it would be OK until the next time.
I replaced the thermostat, with a Stant, and I have only driven 20-30 miles since then, but after driving a short distance, 2-3 miles, the coolant expansion tank, which started out between min and max is full to the cap, and if I continue driving, it will force small amounts of liquid coolant past the cap, along with steam. All this time, the temperature gauge stays right where it should.After the car sits for a while, the coolant goes back down to normal levels in the tank. I also noticed that the small return hose that goes back to the thermostat housing seems to have coolant and air flowing from it back into the expansion tank, when the car is running, you can see enough through the white plastic of the tank to tell that itlooks likemostly air flowing back into the tank. The coolant looks uncontaminated, green as it should be, and the oil also looks good, and no white smoke from the exhaust, and the engine runs great. Anyone have any ideas? Maybe too much coolant? Maybe air in the system?

Thanks in advance for any help!

CK

 

Maybe thermostat in backwards? Maybe bad thermostat? Something does not sound right that's for sure, and it's not just a case of too much coolant in my opinion.

 

Thanks for the almost instant reply!! I agree that the amount of coolant in the tank is only a symptom. The thermostat is pointing the right way, I made good and sure of that when I replaced it. Since the new thermostat I have not had the actual overheating problem like I had before, but it only happened sporadically, so I really don't know yet. I'm wondering if the cap, although no cracks are evident, is just not holding the correct pressure, therefore allowing this problem to happen. I will swap caps with my wife's 240 when she gets home and see if that corrects the problem.

CK

 

Well,I just tried a known good cap on the expansion tank and it did the same thing. I also detect a faint but unmistakeable "combustion" smell in the expansion tank. and when theengine was sort of cold, when I hold the engine at about 2000 rpm, there are a few (not many) bubbles in the expansion tank with the cap off. So my worst expectations seem to be materializing.. a blown head gasket. Dammit! Does anyone think it still could still be something else?

 

Have the cooling system pressure-tested, preferably at a shop that specialises in Swedish/European makes. If the head gasket is shot, the system would not hold pressure.

Coolant flowing back into the expansion reservoir from the t-stat side is normal.

I wonder if there is a partial blockage within the system, preventing correct flow of coolant.

If all of the above turns out ok, I still would suspect the integrity of sealing between the cap & the reservoir. The original cap (grey) was known to go south, so many people have replaced it with upgraded green version, though I myself found that the older grey version worked better than the new green cap.

Again, if all of the above should turn out fine, I would try with a known good reservoir + cap combo.

Wait to see what Moderator Tech (the top-dog of the forum) thinks.


JPN

 

Sounds like the new thermostat isn't opening.
Not sure why but thats what it sounds like.

 

Thanks again to all who have offered insight! Is it possible to run this engine, as a test without the thermostat at all? I have done this on old Chevys or Fords, but they did not use the O-ring type of gasket so I'm not sure how the thermostat housing would seal to the head.

 

Possible but you would have to make some kind of seal.
Or if you still have it cut the old one apart and just reuse the round part.

 

Stant isn't a goodbrand for Volvo, next time try OEM T-stat; Vernet or Wahler.


JPN

 

I just removed the thermostat again. I just had to make sure I did not put it in backwards, it was pointing in the right direction. I ran the engine for a few minutes with the coolant cap off. The coolant level started just above the Min. level and over about a five minute period, rose to a little above the Max. level. I will be taking it to my Volvo mechanic today so he will have it first thing Monday morning to check it out. I will also ask him to replace the Stant part with an OEM thermostat.
But I have another issue. It may be related, that's why I did not start another thread. If you look at the image below, there is obviously some part missing in the area I have circled. I don't think it would be related to the coolant expansion problem, but since I don't know what it is, I can't be sure. Can anyone tell me what is missing here and if it would have any affect on the coolant problem? Thanks again!




[IMG]local://upfiles/8412/D77C502FC2CC42C1858527B44C3860CC.jpg[/IMG]

 

There should be a black pastic hose there. It would have not impact on you collant problem. I've seen cars driven without that hose.

 

The hose that is supposed to be there is your ECM cooling hose. You can drive without it, but I would eventually get it replaced. It would kinda be like running your home computer without a fan. Its ok to do for a while, but shouldn't do it long. I had to replace mine cuz it cracked, i think it was around 20-30 dollars and easily installed on your own. One end to the ECM box, one to the outlet in the front grill/radiator region.

 

It is really not needed but nice to have.
There is a cooling pipe from the Evap box to the ECU box that also keeps the computers cool.
Anytime the fan is on Cool air is going to the computers and in the summer A/C is cooling them.

Also the slot you seeon the front of the ECU box is for the OBDI on the 1993,1994,1995 cars. The boxes with the ports and LED would slide into the groove.

 

The missing object probably wouldn't hurt much and should not be related to the coolant boil over problem. However, yes heat is one of the biggest enemies for electronic components and I would find a hose at a junkyard or, well, the dealer (probably $100).

I noticed, however, that the expansion tank has some brown spots. The former owner (I hope it's not you) probably neglected it for a long time.

I now wonder if the small coolant passages within the radiator are clogged.


JPN

 

I just have to say it again, thanks to everyone for sharing their knowledge and experience! My mechanic did not get to the car until late yesterday, so I still do not know anything definitive. He is going to perform a compression test this morning and that should answer the head gasket question.
To answer JPN's question, I have only owned this car about 2 weeks. The seller would not allow me to take the car to my usual Volvo shop to be checked out (I've owned 240's and 940's for years) because of the time and distance involved. The seller lived about two hours from the mechanic I use. So I took it to a local independent Volvo shop that I don't know much about. They found a few things wrong, it needed ball joints, missing air guide, small coolant leak in the rubber part of the metal cooling line that runs in front of the firewall on the passengers side, etc. Nothing that would keep me from buying the car because it was priced well below the book value. I then drove it for a week, checking the coolant a couple of times per day because of the leak (it only leaked a small amount). I found a couple of other minor things that needed replacement and took it to my mechanic. He did the work I requested and the next day was the first time it ran hot, it just went from normal to hot in about one or two minutes. This was on Friday late, all mechanics were closed and no place to get "real" Volvo parts. That is why I put the Stant thermostat in the car. In retrospect, I wonder if the small leak in that piece of rubber hose was allowing just enough pressure to escape to keep the expansion tank from overflowing. After my guy replaced the leaking part the pressure transferred to the only other place it could get out, the cap of the tank. Anyway, thanks again! as soon as I find out the results of the compression test and the ultimate fix, be it head gasket, radiator or whatever, I will post here and let y'all know.

P.S. I don't think I have ever wished for a clogged radiator, but given the choice between that and a head gasket replacement, I'll take the radiator!

 

After leaving the car with my usual Volvo shop, the mechanic thought it was just a bad cap on the expansion tank. After picking it up, I admit the symptoms were better. As long as you stayed below about 2500 RPM the coolant would not come out of the cap, but would rise to a little above the max level, but after a couple of miles at expressway speed, coolant was indeed coming out past the cap. It hurt to do it because of the long time relationship I had with my original mechanic, I sort of felt like I was cheating on my wife, but I took the car to another (much more expensive) Volvo shop that I had used occasionally in the past. They called back after a few hours and confirmed that the head gasket was leaking. So I told them to go ahead and replace it. The total bill will be between $1200.00 and $1800.00 depending on what they find once the head is off.

I do have a sort of speculative question for the more experienced members of this forum, Is this a repair that would have you thinking about getting rid of the car? If the head gasket is replaced by a competent shop, have I sacrificed anything with regards to reliability and longevity? Again, many thanks to all that have responded.

 

Sorry this is old news, but I just noticed this and thought you might be interested in the following additional information about that missing duct.
This thread discusses the same issue from when it happened to me. https://volvoforums.com/m_64768/tm.htm
The part number (given in the thread) is: 8619305. I was able to order it through www.eEuroparts.com (I called to order it and they beat the other online prices I could find). It was $15.90 through them. I have been unsuccessful finding a parts car nearby, so for less than $20 I figured I might as well just order a new one.

Hope that helps.

 

I wouldn't get rid of the car.
I would have it fixed.
It will be like it was before the problem started.

 

Thanks again to everyone for sharing their expertise! The Volvo shop has now replaced the gasket, checked and resurfaced the head, and did a valve job on the engine. The cost was about $1500.00, which included a couple of other small miscellaneous repairs, and the car runs extremely well with no overflowing of the expansion tank! Thanks Again!

 

Glad to hear things are fixed. You can think of $1500 as quite a bit of money for a repair, but think about the fact that you can not buy another car as good as the one you have for $1500. I think it's money well spent and I also think that is a very reasonable price for what they did. Very reasonable.