1996 850 AWD Coolant Smell in cabin

[Randomnamegenerator]

Hello All,

Over the last couple of days I have noticed a smell which I believe is engine coolant in the cabin. The smell comes and goes and is not constant.

The smell comes when the car comes up to temperature. The temperature gauge will sit at halfway for the most of drive but can go up to 60% and as low as 45%

I have been keeping an eye on the coolant reservoir over this time and it doesn't appear to be losing any coolant.

Any suggestions, thanks in advance.

[misha]

Temperature gauge MUST always be at 3 o'clock when engine reach operating temperature.
Fluctuating temperature gauge indicates that problem could be bad ECT or bad thermostat.
ECT MUST be OE Volvo.
Thermostat Wahler (oe Volvo)or at least Vernet.

[scot850]

Also check that you are not getting a greasy layer at the bottom of your windshield above the vents to the windshield.

If this is the case, pull the carpet back behind the drivers side pedals and check the bottom of the cabin heater core and check for leaks running down under the drivers side carpet. Don't think that because the carpet is dry on top it is ok. Volvo carpets are rubber backed so you have to lift them to check for coolant under it.

Neil.

[Randomnamegenerator]

I haven't noticed any moisture around the windshield vents but pulled the carpet back anyway after reading heater core is a common point of failure.

Everything looked clean and I couldn't find any fluid or coolant smell so imagine that the heater core is still good? Maybe it's worth running the car until it's up to temp and see if anything comes out.

I will try this when I have the time and if nothing comes will order the thermostat and ECT sensor

[erikv11]

There can still be coolant leaking out of the core and remaining inside the plastic box, which then evaporates and gets sent into the cabin through the vents. If it smells like coolant in the cabin, the core must be leaking.

It sounds like there are two problems here, one in the cabin (the core) and one in the engine bay (the thermostat and/or ECT).

[Randomnamegenerator]

Ok, will add heater core to the shopping list.

Is there a preferred brand or brands for replacement heater cores?

[454cid]

I would not rule out an under hood coolant leak, yet. You've got multiple coolant lines, and the pressure reservoir sitting right by the air intake for the HVAC system. I would use a pressure tester and pressurize the cooling system cold, and look for leaks. When the engine is hot, it's too easy for a leak to evaporate before it can be seen.

[Randomnamegenerator]

Family has been sick the last week so I haven't had a chance to do much with the car other than change the thermostat but still no real difference regarding the smell and slightly above 3 O clock temperature reading.

Is there any value and getting a cheap odb2 Bluetooth connector to see if there are any vaults logged?

My understanding is the car has Bosch Monotonic 4.4

[scot850]

Are you actually losing coolant? Are you sure it is coolant? It could be the evaporator has a hole and you are smelling A/C system oil through your heating system.

Neil.