I think I need a new thermostat. The last few days I've noticed a new anomaly, where shortly after I begin driving, the temps begin to rise, and nothing that I do really seems to bring them down. They'll rise steadily up through the 190's, then up into the low 200's, then this morning it peaked out around 218. Then, right about the time I think I better turn the key and shut her down, the temps steadily decline, and after a minute or less, she's back to steady, normal operating temps, around 186. I'm guessing that the thermostat is sticking.
After looking around online at AutoZone, I notice there are several different choices for the opening temperature of the thermostat. It says the OE recommended ones are the 192 and the 18-something.
So here's my question: Is there any reason at all not to go with the 160 degree thermostat?

 

Per the manual, factory thermostat is 88c = 190F and is supposed to be fully open no higher that 89C, or 192F.
I've found I have to go to a 180 to be fully open at 185-190 which falls in the range stated in the manual.

I guess in the UK thermostats are labeled for when they are fully open, and in the US when they start to open.

I wouldn't go to 160. If a 180 won't work you have a cooling system problem.

 

With a 160 you will be running to cold and your MPG will drop and the heater wont work very well.
I have a 195 in my truck and my truck runs at 196 on the expressway, 198 in traffic.
It even stays at that temp on a 95* day with the a/c on and off roading in deep sand for 3 hours.

 

The one that's in there seems to work most of the time, but appears to be not opening initially. Once it opens, everything is fine. I was driving around at 175 degrees for a little while today, but only after the temps initially rose up to about 218. Then it seemed that the thing popped open, the temps dropped and all was well after that.
So what I'm thinking is, if our cooling systems are so touchy(based on observation of forum content), wouldn't it be more desirable to start the coolant running through the radiator at 160, instead of waiting until it gets up to 190? The only real difference would just be that the warm up period for the engine would be shortened by the t-stat opening 30 degrees earlier. But, as stated previously, heat generation doesn't seem to be a problem for Rover engines.

 

Where are you getting temp readings?

I drilled & tapped my stat housing for mine, as such it doesn't even register until stat opens, after the factory says normal for a while.

You may try dropping yours into hot water (just b/4 boiling), and watch it for smooth operation. (several times?)

luck,greg

 

The temp readings are coming from the ScanGauge. It's nice to be able to see some actual numbers.
I consulted Google for more details on thermostat operation. I was thinking it would either be fully opened or fully closed. The interweb says most will open progressively as a function of temp, so that at whatever temp the thermo guys determine the normal operating temp is, should result in a thermostat that is half open.
Moral of the story appears to be: stick with the design spec on this one.

 

I agree, today (in the 60's) mine opened, temp went to 195, then down to 180, then back to 190, I think it was modulating and then found a spot.

luck,greg

 

Out of curiosity, Greg, in your avatar picture are those holes drilled into the grill of the vehicle for better cooling air flow? I've been bouncing that idea around in my head for a little while, wonder if it would actually make a difference.

 

simply cut out the valve in your thermostat and see if that changes it.

My truck ran at 218 on a super hot day in traffic with a/c on and ne e fan working before head gasket..


By the way does your scangauge show mpg?

 

Before you start playing with the t/stat, have you checked both the mechanical and electrical fans, are they working as they should? How about your radiator, it is old enough to be restricted.