1998 Volvo C70 Overheating and fog on windshield

[Ben850]

To Ben850: I'm pretty sure there are no leaks, since coolant level in expansion tank is steady.

So I changed the heater core, flushed the coolant, put new stuff.
It looks like the coolant doesn't flow through the radiator. I monitored the coolant temp on OBD II scanner (Torque app). At 102 Celsius fan came on but the temp went up regardless. At about 120 C coolant started leaking at firewall connector. But here's the thing: radiator upper and lower hoses were cold. Not even slightly warm. Does that mean the thermostat has failed?
I visually checked the water pump. No leaks there.

It seems like you are utilizing all the appropriate processes to diagnose your issue.
I believe you will find it. Don't give up. The "Ghost" in the machine may reveal itself.

If you have not yet replaced the thermostat, absolutely do that with a Whaler (spelling?), which is OEM and will also usually be stamped Volvo. At the same time, replace the ETC. This is the temperature sensor that screws in directly next to the thermostat. (Valeo is the OEM brand.) These parts should not be aftermarket reproductions. They are two of the specific items in the cooling system that make the car talk to itself and let you drive it.
I had to learn this one last year.

Get one of these. Sorry, you won't get help from my paypal account.

http://www.ebay.com/itm/121376314245?_t ... EBIDX%3AIT

This is OEM but my fault for letting it sit in abnormal cold. The car was not even started in this condition.

Parts.

this part is always fun as well.

There it is for now.

[erikv11]

The thermostat is stuck closed or the radiator is physically clogged. Outside chance the water pump has failed but I doubt it.

(1) Drain the coolant, pull the thermostat out, put it back together with no thermostat and refill the coolant.

(2) Run it.

If it now runs too cool, then the problem was a stuck closed thermostat. Replace it with a Wahler 90 C stat. You can get this part many places, the easiest is usually at the local car parts store sold under the Gates brand. Pull out the stat at the parts counter, it should say Wahler on it, if it doesn't then walk away and try another parts store or order one online.

If it still runs hot, then you have a clogged radiator, that's a more expensive fix. I will only use the OEM Valeo radiator, some people like the Nissens.

By all accounts (the gauge on the dash, the temp when the fan kicks in) the ECT is still working fine, but if it has never been changed then you may want to do it while you have the coolant out. Same for the rest of the cooling system like the hoses etc, make a judgement call. The two small hoses on the turbo cooling lines take a beating, seriously consider swapping those.

[andybbrown]

Good thing you stopped. Alloy head will easily get stuffed

[Volvich]

Thanks so much for your responses! I think so too, most likely the culprit is the thermostat.
I will search the site for a write up on how to change the turbo cooling hoses if teher's one.
The radiator is fairly new, about two years old. I assume the water pump has been changed about four years ago. It had been done before I owned the car.
I will run the car w/o thermostat and will post the results.

[Volvich]

Allright, I got good news and bad news.
The good news:
The "Ghost" (as Ben850 said:)) is the thermostat. Took it out, boiled in water and the sucker never opened.
It took a longer time for the coolant to warm up and radiator lower and upper hoses were warm to the touch by the time I HAD to shut it down.
And here comes the bad news:
Coolant leaked from where the thermostat housing attaches to the engine.
I had cut out thermostat middle part so I could have only the outer metal ring with the gasket on it. But still it leaked. Hopefully when I get a new thermostat this issue will be solved by itself.
During detaching the heater core hoses at the firewall I cracked one of the yellow clips, and it leaks when the pressure gets high.
And the last one, radiator petcock broke It leaked so I had to tighten it more and more. I had inspected the o ring on it before pouring coolant in. It was in a good shape but looked kinda flat for an O ring. anyways, I tightened it too much trying to stop the leak and broke. the threaded half is still in... I believe I will be able to get it out with lets say a sharpened screwdriver or something...
I probably should go and lease a Civic since I'm spending on parts approx. the same plus the time I spend fixing it. But am too attached to this car. Besides I can't take the cheap plastic feel in handling, underpowered engines and CVTs in newer cars...

[precopster]

I had this issue early on in my Volvo career and it ended being the coolant temp sensor. .......they can be tricky little buggers.

[Volvich]

Ordered thermostat along with the temp sensor from fcp. Estimated delivery is wednesday.
It seems a loong wait when you're without a car..

[dosbricks]

Tip: If your temp sensor is same as 850/S70, it is 19mm. If you don't have a metric wrench in that size, a US 3/4" is the same size. An open-end is the only thing that will fit in there at an extreme angle, but it will work because the actual threaded base is very small, brass, and doesn't require hardly any torque.

[rspi]

If the seal on the old t-stat is cracked or you didn't install it, the housing will leak.

When you install the new t-stat, do NOT put those T30's back in there. Install a couple of water pump bolts, hex head. I believe manifold bolts will also work.

If you have the Volvo style rad, they sell those drain cocks a most Volvo suppliers. I have one lying around here as well. The drain cock does NOT have to be tight, just snug.

There is a good chance that you cracked the firewall housing to the heater core. You should probably replace that. They sell kits for it at Volvo parts suppliers as well.

[Volvich]

Rspi you are right, I think the coupler is cracked. I replaced the clip but it leaks anyways. Or maybe the O-rings are bad.
I want to bypass the coupler with heater hoses.
In the meantime I replaced the temp sensor (genuine volvo) and the thermostat (Wahler). Now everything works fine except the major leak at coupler. Anyone has an idea how to get the coupler out? The gas pedal is in the way.
I couldn't figure how to remove the pedal... (98 c70)