What degree thermostat?

[UKPhilTR7]

I want to replace my thermostat as it has not been changed in almost 12 years and I have put on a new fan controller, so thought I would replace most of the coolant parts.

I see that the most common degree thermostat 74 degree, but I see that you can get 82 and 88 degree thermostats.

Would you only use the 88 degree thermostat in really cold weather and is the 74 degree thermostat OK for UK use?

[saabfast]

I think I run with an 82 deg stat but would need to try and find an old one to confirm as the other cars (Saabs) definitely do use that. 74 sounds a bit cool.

[Hasbeen]

I am running the 82C in Queensland where we get many 34C days in summer.

I am running a modern air conditioning unit & an 85 amp alternator to supply the power required.

It was struggling a bit before I fitted a new standard thermo fan. I was amazed at the much higher wind noise when I fitted that, so the old original must have been slipping a lot.

As it is now, with a stock radiator, on the hottest day, in heavy traffic, with the air con running flat out, the needle will approach 3/8 on the gauge, but never gets there. This is at 92C at the top of the radiator, according to my inferred temp gauge.

Hasbeen

[FI Spyder]

I would get around the mid 80's one. You don't want the engine running too cool. More important is the condition of the cooling system, especially older rads. They tend to clog up over time so temps raise and people start going to cooler thermo's or taking them out without going to the source of the problem. The radiator needs to be clean or recored. The other part is you need a thermostat meant for a TR7 with what I call the Triumph foot. The TR7 (and I believe the TR6 as well) has a bypass in the cooling system and without the foot to close it off when open, only part of the coolant goes through the radiator and regardless of anything else you will never get effective cooling that way. Don't depend on the specialists. I ordered a thermostat as a spare and they sent me the wrong one and I had to reorder it (from them) specifically saying I wanted one with the foot. I've never had a cooling problem, even when idling in low 80F heat in traffic. Since mine is FI, I don't have the lean/rich problem to contend with which can also affect it.

[Beans]

Only one option, and that is a 88ºC thermostat. If that doesn't work you need to check your cooling system

[FI Spyder]

An engine runs hotter than thermostat settings so they don't determine anything but when they open. A lower setting won't make your engine run cooler in normal circumstances unless your cooling system is efficient and it is cold outside, you engine may run too cold. The thermostat failed in my Integra and I couldn't get any warm air in the cabin. Thermostats fail in the open position usually, to protect the engine, that's what the spring is for. Replacing the failed (open) thermostat fixed the problem. If your engine is running hot, it's because of other problems (assuming it's opening at all), not because of the temp rating of the thermostat as they should be running hotter than any setting. Their purpose is to bring the operating temps up as quickly as possible as engines don't operate efficiently when running cold. Triumph engines (TR6,TR7) have a bypass so they need a thermostat with the "Triumph Foot" to close it when open so all of the coolant gets directed to the radiator. I don't know about the Rover V-8, probably not. Also a good idea to get one with a jiggle valve to help purge air from the system.