1998 s90, Coolant vanishes, smoke in vents, temp gaugespike

cableguy · Post by **cableguy** » 15 Sep 2015, 15:28

I've been having a bit of a problem with my 98 s90 Volvo lately. I recently had my alternator replaced on the car and has since been having tons of problems. The latest is the temp gauge spikes into the red and the condensation, misty/smoke like air, coming from the vents. No particular odor. As a backstory, the AC is broken so the only thing I use is the heater when it get's cold outside. On top of that, the coolant sign has been coming on so I've been putting 50/50 coolant in car a couple times. Since it kept disappearing I started putting water to see if there was a leak. I don't see any leaks on the ground, in the exhaust and the oil pain isn't milky so not really sure where it is going. The misty smoke started occurring once I started putting water in the coolant. I've been doing a fair bit of research and the only thing I can think of is changing the heater core per some forum advices. Not exactly sure if that will solve the problem but wanted to get advice before given the specific issues before buying the parts and doing major work.

Thanks in advances for all the tip and suggestions.

difflock54 · Post by **difflock54** » 15 Sep 2015, 19:37

If your heater core was a problem you will have wet carpets/underlay and you should smell the coolant.
The heater flow and return hoses may possibly be leaking where they pass thru the firewall.
Check the condition of the coolant overflow reservoir for splits or leaks under pressure and also the cap seal.
When was your thermostat last replaced and /or the temp sensor checked? They can cause the engine to overheat resulting in coolant loss due to excessive pressure.

cableguy · Post by **cableguy** » 16 Sep 2015, 12:09

I'll check for the overflow of coolant under pressure. I'm not sure when the last time the sensor/thermostat where checked. I just got the car a couple years ago and don't drive it much. Can you elaborate for me how the thermostat or sensor can cause the engine to overheat.

difflock54 · Post by **difflock54** » 16 Sep 2015, 17:57

Basically the thermostat when not functioning correctly will prevent or restrict the flow of coolant in the system eventually resulting in the engine overheating or running hotter than normal.
If the system is too hot the pressure in the system will also become too high and may cause coolant loss via a faulty reservoir or cap?
An additional issue could be the engine cooling fan not starting up properly and this is where the temp' sensor function could possibly play a part?
A faulty temp' sensor would also account for the temp' gauge rising above normal range.
I note you have not mentioned any issues with the fan or excessive run-on after shutdown so it may not be relevant.

cableguy · Post by **cableguy** » 17 Sep 2015, 17:39

Copy on the thermostat, makes complete sense. Don't know how to check for faulty sensor so might have to take it in.

The fan is actually a good point. The fan on the car keeps going long after the car stops. It basically sounds like the car is still running. I just took that to mean that the car was just trying to cool down before shutting off since it's been hot out.

C.

difflock54 · Post by **difflock54** » 17 Sep 2015, 18:23

If the engine temperature is above normal range the fan would and should come on to lower the coolant temperature. (around 100 degrees C)
It is normal for it to stay on for a short period in such circumstances but needs to switch off after a period of time when the temperature drops back to avoid undue draining the battery particularly when the engine is switched off.
(problems with rad' fans are often due to the failure to turn off)
If your going to take the car in for a check over you might be advised to get a compression test or a coolant analysis done to actually rule out a possible head gasket failure being the culprit.