Thermostat Replacement Advice

[abscate]

The Volvo repair manual says that the pin should be at 1 O'clock when installing the thermostat.

I sure don't remember doing this when I did my radiator and thermostat , now I have another thing to keep me up at night.

[Chuck W]

Before you get into it, are you getting any errors from the ECC module? (Are the lights flashing on start-up?)

You might have a bad damper door motor.

You also didn't mention whether the temp gauge drops when the car is moving.

[callahanoffroad]

Before you get into it, are you getting any errors from the ECC module? (Are the lights flashing on start-up?)

You might have a bad damper door motor.

You also didn't mention whether the temp gauge drops when the car is moving.

I have the old fashioned manual climate control, so no ecc. It's a base model.

Temp gauge doesn't go down. I've already replaced the entire cooling system with the exception of the thermostat. So that was all that was remaining on the list.

[Chuck W]

OK, still. If the gauge is staying "warm" while moving, that should mean the coolant is warm enough to heat, even when moving.

Whenever I've had the issue with lack of heat while moving that is thermostat-related, the engine temp also goes down.

It almost sounds like a recirc or ventilation door is not closed.

[erikv11]

The Volvo repair manual says that the pin should be at 1 O'clock when installing the thermostat.

I sure don't remember doing this when I did my radiator and thermostat , now I have another thing to keep me up at night.

Unhook the reservoir and move it into the engine bay so it is below the level of the stat housing cover, pop off the cover and check the orientation. I've done this, you may spill a little bit of coolant but not much.

OK, still. If the gauge is staying "warm" while moving, that should mean the coolant is warm enough to heat, even when moving.

Whenever I've had the issue with lack of heat while moving that is thermostat-related, the engine temp also goes down.

It almost sounds like a recirc or ventilation door is not closed.

The needle on the gauge barely (or doesn't) moves at all through a wide range of temperatures, it is not very sensitive. So the engine temp may indeed be down - live data would clear that up. Anyway, OP has changed everything but the stat, probably worth finishing the overhaul regardless.

[WhatAmIDoing]

The needle just has to be barely in the white for you to have heat when stopped. I bet the problem is the door is stuck for the heat, or the heater core failed. When driving on the highway in weather below freezing, your temp gauge would be well below the 3 o'clock if the thermostat is stuck open.

[callahanoffroad]

Just to clarify.

I have heat.

I especially have heat when I idle the car in the parking lot at work after driving around.

When I start driving (the water pump starts rapidly circulating) the heat diminishes. It doesn't go away. It's just noticably less. I suspect my thermostat is either stuck open, or more likely opening too early

Either way, I still need to replace the thermostat as it's the last piece of the cooling system that is 1995 original.

Does anyone have a diagram for a non-ecc climate system? I did a cursory search online and only saw ecc diagrams.

[Sommerfeldt]

Each time I've had to change the thermostat, the temp gauge both on my 95, the current 96 and the 98 S70 would go down while driving and back up to middle when standing or crawling in traffic.

WhatAmIDoing and Chuck W has a very valid point - if the needle stays smack in the middle, the problem is likely to be somewhere else.

I've always been lucky with the thermostat changes, I guess... a long T40 and a good smack on the handle always break those torx screws free in my experience - knock on wood, have never stripped one so far.

- S

[Chuck W]

Does anyone have a diagram for a non-ecc climate system? I did a cursory search online and only saw ecc diagrams.

This what you're looking for?

MCC Manual

[oragex]

This is how to quickly test most thermostats. On most engines (but not all of them) the thermostat fails in more or less the open position - which causes coolant to flow continuously through the radiator even with a cold engine. The wider is stuck open, the less the coolant temperature. On a stat that's stuck very open, the temp needle will drop when driving at speed such as on highway in winter time because then the radiator gets cooled more by the air flow.