View Full Version : TR2/3/3A TR3 Running Hot

07-18-2009, 11:01 AM
Well, ever since I got this car together, it's been running a little on the hot side. Initially in the 190-195 deg F range. If it stayed there, I wouldn't mind so much, but now that the weather has heated up some more, it's starting to run more like 200-205 F.

Here's what I've got, and what I've observed. Engine has 87mm pistons, head shaved for compression increase, and a mild cam grind, so the engine isn't stock.

No engine driven fan, as I have rack & pinion steering. Electric fan is only a 10" fan, as that is what came with the rack kit. Radiator is new without the crank hole. The cardboard grille deflector for the radiator is in place.

Temps will remain in the 200-205 deg range with the car on the highway at 60-70 mph whether the electric fan is on or not. Air fuel ratios are running 13-14 while cruising at those speeds. I put on a 7 lb cap, but just as a measure to increase the boiling point of the coolant. I had a 4 lb cap on previously. Timing was initially set statically at 4 deg BTDC and hasn't been touched since.

I took the thermostat (original sleeved type) out today to check it's action in a pot of water. The thermo is marked 80 deg C (176 deg F) It starts to open at just about that temp, and is fully open by 185 deg F.

What am I missing here?? And what might I look for to try and bring these temps down a bit??

Edit: I rebuilt the temp gauge myself during the restoration, but temps throughout it's range was verified in a pot of water and an accurate thermometer, so I feel the the temps the gauge is giving are correct.

07-18-2009, 11:12 AM
The radiator cap has to be longer than what you commonly buy today. I thick it is a 1" cap instead of a 3/4" cap. If you use the short one you will never build any pressure and the boiling point of the coolant will be lower. The 3/4"/1" refers to the depth of the radiator neck to the sealing surface. Let me know if you need the NAPA part number for the correct cap.

07-18-2009, 11:14 AM
Whats your coolant to water ratio? If its just some 50/50 Prestone stuff, then I would go with dumping that and doing the mix yourself. Personally, I would try 25% coolant to 75% water, then dump in a bottle of Redline water wetter. 10 to 1 says that solves your hiccup.

07-18-2009, 11:16 AM
Art- Isn't yours a new motor. Won't you expect a little warmer with a new one?

07-18-2009, 11:19 AM
The watter wetter most likly solve your problem It dropped my temp about 5 to ten degrees,

07-18-2009, 11:28 AM
OK, to answer all of the questions...

The radiator cap is the proper one that has the one inch depth.

The coolant is a 50/50 mix (I mixed it myself).

And yes, the engine is newly rebuilt.

I can easily try the drop in coolant percentage and the water-wetter (which I've heard pretty good things about), but there just seems to be something systemically wrong here that I can't put my finger on.

Keep the ideas flowing...lots of good ones so far.

Edit: What about closing down that by-pass hose a little more. Even though I have the sleeved thermostat, would putting in a plug with a small hole in the by-pass hose help out?

One other thing, I have the heater by-passed. I put in a hose from the two heater tubes instead of running through the heater. I didn't trust the viabiity of it when cleaning it out.

07-18-2009, 11:37 AM
Hey Art,

How about going with a summer thermostat? one of the 160 degree ones might help a bit too.

About your fan- I noticed that the one that came with the R&P conversion was less robust than the one that came with my aluminum radiator. By "robust" I mean that visually the fan motor assembly is much more meaty on the one I already had as compared to the R&P one. Mine is a Sparco 6 blade I believe (not sure of diameter, I'll measure for you when I get to the car).

When my fan kicks in, I notice a pretty immediate drop in temperature, both at idle and at highway speeds. Do you notice the same with yours?


07-18-2009, 11:52 AM
When my fan kicks in, I notice a pretty immediate drop in temperature, both at idle and at highway speeds. Do you notice the same with yours?


Well, if you notice a drop in temp at highway speeds also, then maybe that peanut fan I got IS just too small. It just seems that on the highway, the temps pretty much run the same whether or not the fan is on or off.

Gavin, see if you can find out which fan you have on there and let me know. Maybe that really is the problem.

As far as the thermostat goes, if it's fully open at 185 deg, I don't have a problem with that. All that a lower temp thermo would do is open sooner. I can't control 185 deg, so I certainly won't be able to control 160 deg.

07-18-2009, 01:55 PM
Art --
Mine runs about the same as yours.
Verified temp gauge & 160 sleeved T-stat.
Yellow plastic fan behind original (cleaned out) radiator.
New (correct length) 7# cap.
Heater connected and working.
50/50 coolant mix.
87MM jugs and Isky "TR23" cam -- all else, pretty much stock.

I don't worry about it much, though I do keep an eye on the temp gauge. It runs warm on the road and definitely gets warmer in very slow traffic. I am comforted by the facts that it recovers quickly when I get it moving again, and that I haven't boiled it yet. It can be running over 200 while I'm cruising, and and the act of pulling onto the off ramp and going down through the gears as I decelerate will bring it right down to 190. I wish I had more "head room," but I seem to have enough. In ambient temps < 70F, it works fine. I haven't seen 100F yet, but I've driven it on a several 95F days.

07-18-2009, 02:29 PM
"If you use the short one you will never build any pressure and the boiling point of the coolant will be lower."

I don't believe that raising the boiling point will make it run cooler.

"Edit: What about closing down that by-pass hose a little more. Even though I have the sleeved thermostat, would putting in a plug with a small hole in the by-pass hose help out?"

If the t-stat housing is eroded the t-stat sleeve won't shut off the bypass completely. If that is the case a plug with a hole in it and a normal stat, might as well go for a 160, will help.

"One other thing, I have the heater by-passed. I put in a hose from the two heater tubes instead of running through the heater. I didn't trust the viability of it when cleaning it out."

It's nice to have the option of the additional coolant in the heater circulating if need be. Not comfortable to the driver, but nice if needed.


07-18-2009, 03:17 PM
At least with the Smiths sleeved thermostat and thermostat housing I checked, the sleeve doesn't come anywhere close to closing off the bypass completely.

FWIW, Art, I fought a similar problem with my TR3A for most of a year, before I finally asked my radiator guy for help. Even though they had previously rodded out the radiator and tested that it flowed OK (as well as not leaking); this time they checked it for thermal efficiency and found it severely lacking. With the original radiator (and apparently some replacement cores), the tubes go through holes in the fins, rather than the fins running zig-zag between the tubes. On my radiator, the tubes were apparently no longer in good thermal contact with the fins. Possibly a previous overheating episode had left the tubes deformed, or maybe there was just corrosion down in the joints. Anyway, a new core solved all my problems instantly. My radiator guy said the same thing can happen sometimes with the "zig zag" style radiators.

I don't believe the fan (either mechanical or electric) should be needed at speed. If you are having to run the fan at speed, then IMO there is something wrong.

Also, for maximum cooling (at the expense of slower warmup); what I do is block the bypass entirely and drill a hole in a (standard type) thermostat so that it always allows some water through the radiator. A 3/16" hole seems to work well for me. But this wouldn't be suitable if you either drive the car in very cold weather; or if you are in the habit of using full throttle before the engine is warm enough for the thermostat to open.

Also BTW, I believe a higher system pressure can actually lower coolant temperature by a small amount; by improving heat transfer between the water and the radiator tubes. This is the same theory behind Water Wetter.

Yet another thing to check is the water pump impeller. I have heard of them coming loose on the shaft, or being eroded to uselessness. A quick visual inspection might not be a bad idea, if all else fails.

And while I'm sure you've double-checked the fan belt tension, I'd do it again. Can't count how many times the front lower bolt on the generator worked loose on me (before I switched to an alternator, then the bolt into the water pump housing always worked loose).

07-19-2009, 10:51 AM
OK, here's the happy update... :smile:

I dumped in a bottle of Redlne's Water-Wetter and made up a plug with a 3/16" hole to stuff in the by-pass hose.

The car runs at about 187 deg...just a needles width above the 185 mark. Above about 30-40 mph, the fan is not needed. Temp just hangs at that 187 mark. Slower speeds and alot of idling brings the temps up higher then that, but turning on the fan drops them back down to the 187 mark again...although it does it slowly. I need to replace the peanut fan I've got in there with a bigger one, but for now, I'm a happy camper. :banana:

BTW, one thing bugs me about this...

Was it the Water-Wetter or the by-pass plug??? Or both??? :laugh:

I'm leaning towards the by-pass plug. Time for a Sierra Nevada, and thanks to all who responded. :thirsty:

07-20-2009, 11:44 AM
That's great news Art!

To update you on my setup- I have a 12" Spal on mine. I PM'ed you the details, but for others who are interested, here is the website:

SPAL (https://www.spalusa.com)


07-20-2009, 07:12 PM
OK... Read and learn. That's what this place is good for.
What a simple & effective mod!
3/4" copper pipe cap: $0.45
3/16" drill bit (since I didn't seem to have on lying around): $0.85
You don't even need to drain any coolant. Just pop the bypass hose off the t-stat housing, stuff the drilled pipe cap inside the hose and reconnect it. What, maybe 15 minutes total?
And then the car runs cooler -- rather substantially cooler!

Maybe Water-Wetter would make it cooler still, but it's $10.00.
This $1.35 mod may be all that's required...

07-21-2009, 03:19 PM
Hi Art I think it is running too hot. What kind of fan do you have on the engine? I use a tropical fan and a 160 sleeved thermostat with no electric fan and mine runs about 160 to 180 in light traffic. It will get hot idling after perhaps 10 minutes and the hotter it is the quicker it will heat up at an idle. I drove it over to Yakima in 103 degree weather and it did not over heat. I drove in normal traffic and it reached maybe 190+, but it held that. I think yours is running hot because of your engine fan, but again I am assuming that you are using a stock fan on the engine.

07-21-2009, 03:31 PM
As I mentioned earlier, I have NO engine driven fan, only a 10" electric fan. My thermostat tested out as starting to open at 175 deg F and was fully open by 185 F. I'm OK with it running at 185F and being able to drop it down to that if it starts to run higher and I have to turn the fan on. I'd just like to see it drop a bit quicker. I'll get a larger electric fan and that should take care of that problem.