View Full Version : TR2/3/3A Quick Question on Thermostat

07-03-2014, 12:18 PM
Was having some cooling issues with my TR3. Just removed the thermostat this morning to check it out. It is part 2236 and is marked as 72 C (which is about 162 or so F, so summer setting). According to my digital thermometer (accuracy unknown) it seems to start opening just before 140 F and appears to be open as far as it goes by about 175). Quick question, is it fully open in this picture? Do these temperatures for opening seem about right? Thanks, Mike


07-03-2014, 02:05 PM

that bellows certainly seems to be working properly - when they fail the bellows cracks and they won't open at all.


07-03-2014, 02:50 PM
Thanks Randy.

07-12-2014, 07:25 PM
Reinstalled the thermostat, but overheating continues. Car rises to temperature (185 on gauge) and stays there for about 2-3 miles or so and then slowly creeps up in temperture so that in another 2-3 miles it is nearing 2/3 to 3/4 on gauge. Never boils over per say but not good. Was OK in first couple of short runs in Fall but is now acting up. Still only about 250 miles on clock. If I take out thermostat completely should I block bypass or leave open?

Just installed rebuilt distributor (by Jeff at Advanced Distrubutor) as well and it may be timing is still not set up properly and contrubuting to overheating. Been reading all the timing threads so that needs to be checked too.

Suggestions on how to proceed most welcome. Cheers, Mike

07-12-2014, 08:50 PM
If it was OK last fall and not OK now, you should definitely check your timing. A lean fuel mix will also cause it to run hot.

Don Elliott
07-13-2014, 02:40 PM
Mike - I would think it's the timing adjustment. Try moving the vernier one way first till it lugs on acceleration in 3rd or 4th gear. Then move the vernier small steps at a time till you start to hear it ping on acceleration at 1000 to 1500 RPM in 3rd or 4th. Then back off the vernier a bit till you have no pinging. That's the way I have timed my 1958 TR3A for the last 56 years.

Save me a place next to you at the Britannia Bay British Car Show.

Cheers Don Elliott

07-13-2014, 02:47 PM
Thanks Don. Hope I get this overheating sorted out or I won't have the 3 there, and the 6 is under the weather too. Look forward to seeing you next weekend. Cheers, Mike

07-13-2014, 09:08 PM
I wouldn't say that 185 is overheating. What is the outside air temp now compared to "last fall". It can make a huge difference in how hot the engine runs. I have found that if the outside temps are above 70-75 then my TR3 will stay around 185 until at a stop light, and if I don't flip the electric fan on the temps will start climbing right away. The electric fan will keep it at 185. If the outside temps are down in the 50-60 range (or cooler) things are much better. Are your temps going up to 200-220 while cruising, or while stop and go?

07-14-2014, 09:52 AM
Going up while driving ...

07-16-2014, 07:04 PM
If I take out thermostat completely should I block bypass or leave open?

IMO it won't make any difference either way; but with the Tstat out you might as well block off the bypass for maximum flow through the radiator. Geo Hahn's trick of sticking a copper pipe cap inside the hose is better than what I did (tap the housing for a plug).

"2-3 miles" seems pretty quick with ambient only in the mid-70s. I'd be looking for something major like a slipping fan belt (have you checked the front generator mount?) or defective water pump. If ignition timing was that far off, I think you'd notice the lack of performance. Wouldn't hurt to double-check valve timing and mixture, though.

Dad's TR3A acted like that a long time ago, and I believe the root cause was worn carb jets and/or needles. They wear mostly at the idle position (especially if the jets aren't centered just right), causing the mixture to go rich at idle. Then when you adjust at idle, the cruise mixture goes lean. Unfortunately, I changed rather a lot of things at the same time, so I'm not really certain of the diagnosis. Kinda teed me off, having to rebuild his car engine during my Xmas break, especially since there was no room in the garage and I did it laying in the snow. Wanted to make sure it never happened again! (and it didn't)

07-16-2014, 09:45 PM
Thanks Randall. I'll keep trying to sort through all the possibilities. Appreciate everyone's input very much. Cheers, Mike

Don Elliott
07-17-2014, 05:27 PM
Mike - There's still time to try a small thing. Check the level of coolant in the fill box and you should have about 1/2" of coolant that you can see when you eye-ball straight down to the bottom of the fill box. Then start the engine with the radiator cap still off. When it gets up to 180 F or so, take it for a drive - with the cap still off. Watch the gauge. If it climbs higher, check the coolant level. If it has dropped, add some water. This would happen if the air lock escaped. Then put on the cap and head home again.

My thought is that you may have an air lock in the system and it will escape with the cap off. It has been the lurking cause of many TRs overheating. BTW, I have heard that 20% antifreeze and 80% DI water will give better heat transfer than a 50/50 mix. I have been keeping to the 20/80 mix for years.

07-18-2014, 07:48 AM
Thanks Don. Will see you Saturday. Decided that worst case I will trailer car most of the way :-(

Cheers, Mike

07-20-2014, 11:45 AM
In any case you should not remove the thermostat. these cars are designed with an excess of cooling capacity. if you remove the thermostat the engine will not get up to spec temperature, clearances will be off as a result, and excessive wear results. I think the others are right, it is either too lean/vacuum leak, or timing too advanced. or poor coolant flow - blocked up radiator, defective pump, etc

07-20-2014, 12:55 PM
In any case you should not remove the thermostat.
I assume he meant only as a test. Otherwise I agree, you shouldn't run for very long without a thermostat.