Lazy Thermostat?

[Stu Twin]

Here's an odd one. (to me anyway}
Back in early Sept, the rad in the Dodge developed a small leak. I had planned to get it recored anyway, so I thought I'd stick some Radweld in that I had as a temporary fix. (not keen on the idea tbh but thought it better than nothing)

Soon after I went to a local show and about a mile from home I got stuck in a queue for about 10 mins.
Temp gauge (the one in the dash which was rebuilt by the way by Autoinstruments about 8 years ago) rose higher than I've seen before, so at the next opportunity i turned off the main road and took the long way just to keep moving, Sure enough the temp settled down almost immediately.
It was fine on the way home.
So thinking the thermostat was playing up I fitted a new 180 deg stat and sender.
Went to the Croxley Green show the next day and it seemed fine with no repeat.

Soon after, on the way to the MOT, and without even getting stuck in traffic, the temp did the same thing. With the gauge almost fully over to '11' i had a look under the hood and while it was hot there was no sign of steam or overflow. Soon after the temp subsided, so I carried on to the MOT. No reports of any problem from the MOT garage (cheers Jim).
I think it was also ok on the way to Thunder road.

So the other week I got Kempston Rads to do a recore, Great service btw, 4 day turnaround. Nice new 4 row core with closer pitch tubes. Takes about 1,5 litres more coolant.
All fitted in time for a test run to the Goat last sunday and guess what, it did just the same thing. Temp gradually rising while cruising along until it reaches max,then settles down to normal.

Is it likely to be 2 sticky thermostats? (no, i haven't tested the 1st one in a saucepan yet)
Can't see why it would be the gauge giving a false temp reading because what would cause the spike?
Is it worth flushing the block out?
Get a 160 deg stat? or Hi flow stat?

Sorry for the essay.
Confused of Hitchin.

[SJH]

The first thing I would do is to check the temperature you are seeing at the gauge is actually correct. I have used one of these infra red temp guns from ebay (about £12) for a second opinion. Once you have shown the sender/wiring/gauge are correct then move onto an actual overheating problem.
IMHO 160 deg is a bit low to run well.

cheers
Shayne

[Stu Twin]

Thanks Shayne,
So I suppose if you pointed the sensor at the actual rad, it would be roughly the same temp as the water inside?

[SJH]

Thanks Shayne,
So I suppose if you pointed the sensor at the actual rad, it would be roughly the same temp as the water inside?

You could point it at the thermostat housing/take off point for the temp sensor as well to get a feel for the temp compared to the gauge. Then look for a rise in temp when it happens on the gauge. Given time to warm up properly the water should heat its surroundings to a similar temp.

I had a similar problem on my Vauxhall Ventora. I checked the temp with a infra red gun and a thermocouple wire in the top hose and both were similar and were as expected. Whereas the gauge showed too hot.

Shyane

[Adam]

You have got the thermostat installed the right way round, right?

I wouldn't worry if it's not pushing any water out of the overflow (assuming you've got an appropriate pressure cap). I suspect the guage is playing up?

And yeah, boil up that old thermostat with your breakfast egg to rule that out.

[Stu Twin]

You have got the thermostat installed the right way round, right?

I put it back the way it came out.
Pointy bit upwards ie you can push the centre down from above to let the water through.

[Adam]

There should be an arrow on it to denote the direction of flow, but yes, that sounds right.

[Stu Twin]

Thanks guys, i'll try to remember to borrow the temp probe from work when i next use the car, and see what the real reading is.

[morgan]

I've got the opposite problem. Temp guage never moves until i am sat in traffic.
I dont think its a mile out though as the car wont boil over until its wayyy high (like going into harpenden show) - its the only time it moves !
New rad, new stats - still the same....

[Pete]

Do you have a Radiator Shroud, that often helps with a bit of consistency.

It may be worth reverse flushing the block whilst you are at it.