TR2/3/3A TR3 Overheating I think??????? Problem Found

[Earl]

Folks,
My 61 TR3A has a problem. I'm just coming off a year long rebuild and to date have not driven the TR. But when it runs the engine temp rises and rises until I shut it off when the needle gets close to the top of the gauge. About 10 minutes. The water temp in the radiator is hot to the touch but certainly not boiling.
How do I determine if the water pump is not working, or if the gauge/sending unit is bad. BTW there is no thermostat in the car, and the temp gauge is electric. I really don't want to change out a water pump if I don't need to.
Thanks
Later in this thread I attached a couple of photos of the car before our rebuild and current.

 

[TR4nut]

Re: TR3 Overheating I think????????

One of the easier things you might want to do is a kitchen test of your temperature sending unit. I don't know the numbers for a fact, but I thought at room temp the sending unit should have a couple of hundred ohms resistance, but if you stick the sender in a pot of boiling water then pull it out and measure the resistance will be ballpark 50 ohms. There's probably a good Triumph reference somewhere out there that could give better numbers.
Good luck!

 

[martx-5]

Re: TR3 Overheating I think????????

I don't know if this is the problem or not, but the original style thermostat is designed in such a way that when it opens, there is another part of the t-stat that closes off the by-pass hose coming out from the t-stat housing on the driver's side. The by-pass is there for quicker warm-up. My understanding is that if too much coolant by-passes, not enough goes through the radiator to cool down. I've read of guys putting pieces of wood dowel with a small hole or something in that hose to prevent this problem. I would imaging that some flow is always neccessary through the bypass. I would figure a way to partially block up that hose right now to see it is the problem. Maybe you can clamp it shut or something. Eventually, you will need the proper thermostat.

 

[Banjo]

Re: TR3 Overheating I think????????

YOu can use the same test that TR4nut suggested but you likley have the capillary type temp guage (if its original)
Set up a camp stove or hot plate somewhere near the car so you can reach the bulb that was screwed into the goosneck over into the pot of water. Then monitor the temp with a kitchen thermometer and on the guage at the same time. That should varify if the guage is working correctly.
If it is, and the engine really is overheating, I would look for a partial blockage or the bad pump.
Look for a stuck T-stat, and proper instillation (spring twards the engine) andmake sure the goosneck housing is clear.
I actually came across an MGTF that had that completely blocked with corrosion. It made for some really weird symptoms.
Bout the only good way to check the pump is to remove it. Sorry.
Good luck in the hunt.

 

[TR4nut]

Re: TR3 Overheating I think????????

I agree with mr. martx-5, you should have a sleeved thermostat in there to blank off the bypass when it opens. Moss has a good reproduction, but a little pricey.

But here's another thought on the electrical side: Is your gauge retrofitted from something like a TR4? Gauges on my TR4 run through a voltage stabilizer first, which I thought knocks down the voltage. Even if the sender were working properly, if you had too much voltage across the gauge you'd get too much current which would make it read high. Then again, I don't have a electrical engineering degree so I could be completely full of baloney.

 

[Geo Hahn]

Re: TR3 Overheating I think????????

I partially block the bypass hose with a 3/4" copper pipe end cap with a 3/16" hole drilled in it. Some say that's good, some say that's bad -- so use your own judgement.

As mentioned before... and infared thermometer is handy for seeing what is really going on temperature-wise. I think Harbor Freight has them on sale at the moment.

 

[MGTF1250Dave]

Re: TR3 Overheating I think????????

Aloha Earl,

You said you are using an electric temperature gauge. If it is from a TR4, it needs a voltage stabilizer to provide a constant 10V source of power. These are available from the usual sources or there are a few web pages that will tell you how to make your own solid state unit.

A quick check to see if voltage is affecting the temperature reading is to change engine RPM. At higher RPMs the generator voltage output will increase and the Temperature gauge will increase. By slowing to idle, the voltage output will decrease and the temperature gauge will decrease rapidly.

I doubt you would get the engine as hot as you describe in ten minutes even if the water pump was not working.

When I bought my current TR3 it came with an electric temperature gauge. I was initially concerned about over heating, after running at high way speed for ten miles the gauge would be pegged at the high end, but there was no indication of boiling over at the radiator. After stopping at a traffic light and sitting at idle for a few minutes, the gauge would drop to below the normal temperature range(mid point). On previous TR3s I'd driven my experience was opposite of this, temperature rises at a stand still and decreases at road speed.

Safety Fast,
Dave

 

[Alan_Myers]

Re: TR3 Overheating I think????????

[ QUOTE ]
BTW there is no thermostat in the car...

[/ QUOTE ]

The TRactor motor *always* needs a thermostat installed. It shouldn't ever be run without one. It's quite likely that's why the engine is overheating and would be the first thing I'd try to rectify the problem.

In general, the racing community tosses the t'stats from their cars all the time, looking for maximum cooling.

When TR3 and TR4 became popular on the race track, racers did the same but quickly found out the 4-cylinder engine would almost always overheat if there wasn't a t'stat installed.

There needs to be some restriction in there. I've heard various opinions and explanations why.

I agree the rarer and more expensive sleeved t'stat is the way to go, if possible. However, Geo's method with a standard t'stat and a restriction in the bypass hose seems to work fine too (my TR4 never overheated with that sort of setup, I've recently installed a sleeved t'stat though.)

Incidentally, the method racers ended up using with TR4 was to warm up the t'stat in a pan of water on the stove, until it was fully open, then break it and jam it in the wide open position. That gave the restriction that was needed to keep the car from overheating and maximum cooling at all times. This modification is not recommended for the street or for anyone who ever might want to use their already rather anemic heater.
/ubbthreads/images/graemlins/cheers.gif

p.s. If the water pump isn't noisy or dripping coolant out under the pulley, you probably don't need to be concerned about it. Just be sure the belt is adjusted properly, not too tight or too loose, to get good long service life out of the water pump. Even if it fails, it's not a big deal to change. In fact, there is an upgraded, 6-bladed version I highly recommend, available from www.britishframeandengine.com.

 

[Adrio]

Re: TR3 Overheating I think????????

I agree with MGTF1250Dave. The temp gauge on my TR3 was the same (electric with no voltage regulator). I had the same overheat all the time until I put in a voltage regulator (I used a solid state one I built) and then the problem was gone.
I have done the boil the sender and ploted the resistance versus temperature as well as characterized the electric gauge on displayed needle position versus input if anyone is interested. You could then use a OHM meter on the sending unit to determin the actual temperature of the engine.
In short if you have an electric gauge (and I assume so from the use of the term "sending unit") then installing a voltage regulator is your first step.

 

[Bob_Muzio]

Re: TR3 Overheating I think????????

Earl, you've gotten a lot of quality input. The fastest way to see if the car is running hot/guage accurate is to shoot the upper radiator hose with a lazer thermometer.
You do need to get a stat in the engine though, either the sleeved variety or a domestic design with the bypass hose plugged (with a 3/16 hole drilled for some flow).
Bob

 

[Don Elliott]

Re: TR3 Overheating I think????????

If you plug the bypass hose, you need a small hole 1/8" or 3/16" diameter drill hole will do. The hole is essential to allow the air bubbles to escape and the water to rise when you are filling the empty rad system. I tapped the inside of the housing and inserted a pipe plug (1/8 NPT ?) which I had pre-drilled with the small hole mentioned above.

 

[TRTEL]

Re: TR3 Overheating I think????????

Earl,
All great info, the only thing I would tack on if in fact you work your way thru and still have a problem is check the core. It doesn't take much scale to ruin the heat transfer greatly. Do you live in a hard water area? Anyway I've never been a great fan of rodding out cores, they've always leaked on me too soon afterward. And chemical flushes are OK for maintenance, but really don't cut it for a cleanout of heavy scale. So it's sort pay your money take your chances. Most racecars including mine usually have a denser core, the 'L' core I think, and that usually cures overheating on a streetcar, but you lose your crankhole. Let us know the outcome.
Tom Lains

 

[Earl]

Re: TR3 Overheating I think????????

Thanks Folks,
You've all given me a lot to think about. Sorry about this but after reading the respones I realized I may have left out some pertinent information. The rad sat in my garage for 20+ years when the car was dismantled. I ran the car 20+ years ago without the T-stat with no problems. The t-gauge is an inexpensive after market from 25+ years ago. Also the water pump is NOT making any noises, and it is NOT leaking. But I'd still like to know if water if flowing.
Thanks to all your input this weekend I plan to get the bottom of this problem. I'm going to start with the test suggested by Banjo. Next the T-stat cover comes off and a full check of that area will dictate where I go next. I'll keep you all informed.
Thanks again.
I don't know if I can attach any photos on this reply, so I'll add a new post with a before and current shots.
Thanks again for all your help

 

[Earl]

Re: TR3 Overheating I think????????

The Before Photo

 

[TR4nut]

Re: TR3 Overheating I think????????

Earl-

I'm sorry, but from your pictures and description of the temperature problem, you're car is a goner. Of course, I'd be happy to take it off your hands at a modest price.. /ubbthreads/images/graemlins/grin.gif NICE car, good luck with it!
Randy

 

[Earl]

Re: TR3 Overheating I think??????? Problem found

Thanks for all the help folks. Saturday I went to my local hardware store and purchased a thermometer used for frying turkeys. Next I removed the sending unit from the TR and put it and the turkey thermom. in a pan of hot (150+ degree) water. Within a couple of minutes the turkey thermometer read 150 and the gauge in the car pegged at 250.
This at least tells me that the car was not overheating. Next I'll get a new sending unit then repeat the experiment. If that produces the same results I'll get a new gauge. But at least I can keep working on the car without worrying about the overheating problem.