1998 Volvo C70 Overheating and fog on windshield

Post by **E Showell** » 01 Nov 2014, 19:27

Should be expansion tank CAP.

Volvich · Post by **Volvich** » 01 Nov 2014, 20:12

I appreciate your response!
The expansion tank is only two years old, from dealer. Cap is aftermarket but a good quality.
There's no leaks, bubbles or hissing at all... whats the reason you those might be bad?

Post by **E Showell** » 01 Nov 2014, 21:00

Boiling coolant. It is almost always the cap, especially if aftermarket.

Post by **E Showell** » 01 Nov 2014, 21:02

Tank is likely fine. My earlier post was a typo. It should have read cap, not tank.

Post by **rspi** » 02 Nov 2014, 01:24

Just bypass it and drive till the core comes in. Simple 10 minute thing.

Also you should NEVER remove that cap with the car running it motor warm/hot. And please, stop running the car with a known coolant issue. It will only end badly. I call it coolant roulette.

Post by **rspi** » 02 Nov 2014, 01:26

Bypass video:

Replacement video:

Volvich · Post by **Volvich** » 02 Nov 2014, 12:36

As I stated in my earlier post I've bypassed the heater core. The thing is that I'm getting the same problem as I was getting before bypassing except there's no white smoke coming out of air vents (since I've bypassed that). Years ago I had a bad coolant tank, and bad cap at different times, and yes the coolant was boiling, but the temp gauge was always at 3 o'clock position. Now it goes up. I suspect the problem is elsewhere...?

Post by **E Showell** » 02 Nov 2014, 15:28

Could be bad ECT (engine cpolsnt temperature sensor).

Post by **Ben850** » 02 Nov 2014, 20:13

Volvich wrote:As I stated in my earlier post I've bypassed the heater core. The thing is that I'm getting the same problem as I was getting before bypassing except there's no white smoke coming out of air vents (since I've bypassed that). Years ago I had a bad coolant tank, and bad cap at different times, and yes the coolant was boiling, but the temp gauge was always at 3 o'clock position. Now it goes up. I suspect the problem is elsewhere...?

Is your C70 the LPT? There are still two small turbo coolant lines that might leak.

One is at the turbo underneath, the other would be behind the #1 cylinder near the lower expansion tank coolant tube. They all connect to the external metal coolant manifold on the backside of the engine.

Search for drops of coolant in those areas. You simply have a leak. Look for discolored oil, indicating a gasket, or block breach.

Volvich · Post by **Volvich** » 05 Nov 2014, 01:32

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.

1998 Volvo C70 Overheating and fog on windshield

Re: 1998 Volvo C70 Overheating and fog on windshield