• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

What if the thermostat was in upside down?

Share this page

Westfield_XI

Westfield_XI

Jedi Warrior
Offline
Would an upside down t'stat cause overheating? Or would it open anyway at the correct temp and let coolant flow? I am trying to track down an overheating issue in my 1380. The car runs fine, electric fan comes on, but it still gradually climbs to 180 to 210 and if I shut down it seems to get a vapor lock in the pump. That is: it will not cool off even though the car is cruising again and the airflow is restored.

I found that the t-stat was installed with the "cage" side down in the block. I flipped it 180* and the car seems to heat up slower, but still climbs to 210 when stopped and idling. And it is still reluctant to cool down.
 
The t'stat will only operate properly with the "bulb" end submerged in coolant. ISTR this is a 1275 overbored, yes? If so, you could look for a lower opening temp t'stat at NAPA and try that.

Sounds as if you may have air in the system, too. Park the beast with the filler on the radiator higher than the front of the engine, see if you can "burp" any air out of it by squeezing the large lower hose... engine cold, of course.
 
Thermostat has next to nothing to do with the running temp of the car. When the engine is initially started the closed thermostat hastens the rise to "normal" operating temp then it opens. Once it's open it's all up to the water pump / radiator / ducting / etc to maintain a relatively constant temp. Many currently made t'stats are fail open type where if they crap out they do not close. If this happens the only clue something is wrong is a slower rise to expected operating temp. Some temp gauges and senders are not well matched. Before driving yourself nuts shoot the engine with a heat gun to confirm the gauge reading is accurate. Bob
 
But the problem with a thermostat in backwards is that the bulb end, which controls opening/closing, is that it won't be in the path of coolant that's heating up. It'll be on the radiator side where there's no flow and the only heat will be by convection. Might eventually open, but I bet you overheat before then due to little or no radiator flow.
 
If you just want to go out and run it, you can just take an old thermostat and cut the guts out of it (with tin snips).

When you do this all you will have left is a "donut" which is essentially the same as a blanking plate (as used in racing).

It will provide a decent restriction (so that coolant doesn't fly through the radiator).

Engine will warm up slow (and may run a bit too cool), but you can be sure there's no problem with sticking thermostat.

This is really just a temporary idea, but it may be useful as you are working out bugs. It won't matter if it upside down or not.
 
I think that's my next move, last year I was able to take a 200 mile day trip in Southern Arizona ending up in crosstown traffic with the OAT in the 90's without the needle getting over 180*. Meanwhile I need to make a new throttle cable: the old one got too close to the header and melted the Teflon liner. As long as it was hot, no problem, but once it cooled off it locked up solidly.

Oh well, when you build a car from a kit, you learn to expect such things.....
 
Well, it looks like I have had some success. I first removed the T-stat and ran the car with no real change, then I hooked a hose extension to the inlet of the water pump and dropped it into a bucket, just like my raw water cooled boat. This proved to me that the pump was indeed working. I then installed a new 160* T-stat and carefully bled the system. After a drive to warm things up, the temp went up to an indicated 180*, slowly rose to around 200*, and then dropped back to 180*. I then returned home and let the car idle in the driveway with the temp holding at 180*, I then shut down for 10 minutes, re-started and the temp slowly dropped from 200* or so back down to 180*. My problems have usually been after stopping for fuel, shutting down and then getting a vapor lock in the pump. It was just boiling the head dry.... My assumption is that air in the system was being compressed by the boiling coolant allowing the head to boil dry. Then the pump was just spinning in hot air and not pumping coolant. With no air pockets there in just an incompressible liquid which prevents the boiling dry situation I had before. I also suspect that notmhaving any air also allowed the pressure to increase thus raising the boiling point of the coolant.

Anyway, I will try it out tomorrow morning with a run through the canyons to the Rock Store.

Btw, the previous T-stat was a 180* one which tested good in boiling water. I wish I knew someone with an optical pyrometer to check the temp gauge and sensor. My electric fan is wired to come on with the ignition, I believe I will re-wire it so that it is always energized, so that it will run until the temp drops and the thermoswitch shuts it off. Now, if I leave the key on it also runs the fuel pump.
 
Bob, doesn't the thermostat have everything to do with the running temp of the car?

Whatever degree thermostat you have in the car will essentially be the minimum operating temperature of the car. It won't open up until that temperature is reached.

I had to change my thermostat from a 180 degree to a 190 degree for my car to reach proper operating temperature in the winter, or I wouldn't get any heat.
 
Peice of card board against the radiator in the winter works well and does not require changeing thermostat. Gota think easy and cheep.
 
Joe, for all practical purposes the thermostat stays closed until the engine reaches the temperature indicated on the t'stat and then opens. In a perfect world the t'stat would keep cycling between open and closed keeping the temp at that ideal point. In winter conditions it does work pretty much like that.

Under summer conditions (real life) many times the cooling system is unable to maintain this "ideal" temp therefore once open the t'stat goes along for the ride and the temp varies from ideal on upward depending on the rest of the cooling system performance and ambient temp. Bob
 
Back
Top