1998 S70 Overheating

sourcaffeine · Post by **sourcaffeine** » 23 Sep 2015, 21:02

Car started overheating. Just bought the car, and the previous owner said he replaced the radiator. It looks pretty clean so I believe he did that. However it runs hot. The gauge doesn't read exactly at 3 o'clock, just slightly above. But yesterday it started to overheat. On the way to work I had to pull over to let it cool off. Checked the fluids and it was full.

I decided to change the thermostat. Drained the radiator and very little came out, maybe 1 liter. The old thermostat looked good but I put the new one in anyway and threw some more coolant in. It sucked down about half a quart and didn't take any more. Even with it idling, it just stayed at the same pressure. I put the heater on and let it idle, then drove it around the block. It started to run warm, but cooled back down to normal but still didn't pull in any more coolant.

I am at a loss here, and unsure what I should do further.

Veilleuxpbd · Post by **Veilleuxpbd** » 23 Sep 2015, 22:18

Maybe check to have the system properly flushed, as some debris can block the flow and it never hurts!

Post by **abscate** » 24 Sep 2015, 00:16

The coolant capacity is about 7 liters and I get about 4 liters out by draining the radiator with the cap off. If you only get one liter my guess is somone used stop leak, aka 'new engine' on your car in the past and has gummed it up. Until you get that coolant out and refreshed, don't drive it. Volvos take very poorly to overheating - you have seconds, not minutes, from red light to major engine damage.

sourcaffeine · Post by **sourcaffeine** » 24 Sep 2015, 05:28

abscate wrote:The coolant capacity is about 7 liters and I get about 4 liters out by draining the radiator with the cap off. If you only get one liter my guess is somone used stop leak, aka 'new engine' on your car in the past and has gummed it up. Until you get that coolant out and refreshed, don't drive it. Volvos take very poorly to overheating - you have seconds, not minutes, from red light to major engine damage.

Will do a flush and refill today and post back.

sourcaffeine · Post by **sourcaffeine** » 24 Sep 2015, 19:26

Did a flush of the system and it seems to run without overheating so much. Every now and then the gauge jumps a notch or so but quickly returns. Could be the fan kicking in at that temperature, or the cooling system burping. Fluids are lower as I drive it, so it is probably letting air out, and I will add coolant as necessary.

I will post back over the next couple of days and if it is resolved by then, the thread can be closed.

sourcaffeine · Post by **sourcaffeine** » 25 Sep 2015, 21:43

Today it ran okay, with the gauge rising and lowering, I assume from the system burping. However I believe my heater core failed as steam started to come out of my vents with the smell of coolant. Pulled the carpet down and saw fluid everywhere. I am going to order a new heater core and bypass the heater core for now until I can get it hooked up.

Hopefully I will be able to know if the overheating issue has been addressed or not by tomorrow.

Post by **abscate** » 26 Sep 2015, 06:03

A broken heater core will mean no pressure in the system, which will overheat under load.

A new core will fix your problems and I doubt you will have any engine damage since you paid attention to it.

Remember to wash the Dickens out of the cheap eBay heater core if you go that route.

Post by **JRL** » 26 Sep 2015, 06:58

THE GAUGE IS NOT SUPPOSED TO MOVE.... PERIOD.
If it moves up and down even the tiniest bit, you are overheating!
You still have a problem, maybe terminal, maybe not.

Saying all that... after a fill, the level in the expansion tank will drop a couple of times, so you need to burp the system and top it off, maybe 2-3 times,. Hopefully you saved it.
If it continues you may need a head gasket at best

sourcaffeine · Post by **sourcaffeine** » 26 Sep 2015, 07:33

abscate wrote:A broken heater core will mean no pressure in the system, which will overheat under load.

A new core will fix your problems and I doubt you will have any engine damage since you paid attention to it.

Remember to wash the Dickens out of the cheap eBay heater core if you go that route.

I am getting a Volvo OEM heater core, so it should be alright. I will still flush it out.

JRL wrote:THE GAUGE IS NOT SUPPOSED TO MOVE.... PERIOD.
If it moves up and down even the tiniest bit, you are overheating!
You still have a problem, maybe terminal, maybe not.

Saying all that... after a fill, the level in the expansion tank will drop a couple of times, so you need to burp the system and top it off, maybe 2-3 times,. Hopefully you saved it.
If it continues you may need a head gasket at best

When I say it was rising, it was a single notch or so, and returned to normal a few seconds later. I assume something is still wrong with it, but I wont be able to diagnose until I bypass or get a new heater core. I will post back when I've done one of those two.

sourcaffeine · Post by **sourcaffeine** » 26 Sep 2015, 11:21

Bypassed the heater core, and just like expected when revving to 2,500RPM, it begins to run hotter than normal. Cut it off before going too high. Any suggestions as to what to check next?

I am plenty mechanical, I have just never owned a Volvo, although it doesn't seem too difficult so far.