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TR4/4A TR4A running warmer than usual

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carpecursusII

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I have a 4A that has about 1100 miles on a total rebuild. It has run without incident until a few days ago. I have an aluminum radiator, a triumph 6-blade tropical fan, and 160 degree thermostat. Until a few days ago there was nothing I could do to make the car run hot not even 100 degree oklahoma heat, it would barely come off the 160 thermostat temp, suddenly it has decided it wants to run at about 3/4 way up the gauge. It used to sit on the left small dot just shy of 1/2 through the range.

I have drained the system, checked the thermostat in water, and no removed the water pump to ensure it is pumping. The system was clean with no sediment, it was full and all seems to check out. I swapped out sending units on the thermostat and got the same reading so I ruled that out as well. While the car has now started to run warm, it still runs fantastically at all RPM ranges and pulls all the way through 80 MPH. I also took a laser thermometer and checked the exhaust manifold, the outlet off #1 is 100 degrees cooler than the other 3, the other three are within 10-15 degrees of each other with the center two being slightly warmer than #4. I did a compression check and have a solid 148-155 (hot) on all four cylinders. The plugs
(RL95YC) all look similar and do not indicate a coolant leak or other issue.

I am at a complete loss for what is making the car suddenly want to run warm and why the exhaust temp would be so different on one cylinder.
 
Okay, I can never remember -- does a failing voltage stabilizer make the temp gauge read higher? I think so.

As I recall it will also have the same effect on the fuel gauge so perhaps consider that.
 
Just to be clear - I am referring to the dingus that maintains a steady 10VDC for some instruments - not the control box aka voltage regulator.
 
That's the one. I recall that a poor ground may cause it the instruments (temp & fuel) to read high, not sure what other failure modes do. Does your fuel gauge appear to be as accurate as it has always been or might it also be reading high?

I suppose one can measure the output of that stabilizer with an analog meter - a digital meter may not work as the stabilzer is some sort of thermo-mechanical switching that creates the equivalent of 10 volts.
 
Does the gas gauge read funky now? (if you have an idea of where it should be) As the voltage stabilizer would effect both, I don't think my TR4a had one, but it was "restored" by a college kid about 30 years ago, so maybe he forgot to install it, or maybe it had one and I never found it, I see Moss lists them.

Greg
 
Don't know what the Moss test is but you could shoot the thermostat housing with the laser to confirm that it is as warm as the gauge shows. That will also give you a number. If that number is within the operating range, even though hotter than before, I wouldn't worry about it. Of course you could always try another stat. If it fluctuates or keeps climbing, then you'll have to pursue this into the cooling system.
Tom
 
Only thing I can add is to make sure there's no air in the system. Especially since you drained and refilled.

Keep us posted!

Mickey
 
Once warmed up, is it staying at that high point in all conditions (idle, running at speed, etc.)?

Scott
 
Just out of curiosity - when you "lift the piston 1/32 inch" - are you actually lifting the piston directly? or are you using a "lifting stud" at the side of the dome?

On my H6 carbs, I never found the "lifting stud" to really lift the piston, unless I lifted the stud more than 1/32 inch.
 
I have about 2500 miles on my rebuild,no temp issues,but the only things that have changed without me touching is the points closed more than expected after only 1500 miles,this retards timing but probably not enough to cause your problem,and several valves tightened up.
Tom
 
I just redid valve lash and it made no difference.

The car runs consistently at the higher temp, it will come up to it and hold there with only minor variations.
 
carpecursusII said:
I just redid valve lash and it made no difference.

The car runs consistently at the higher temp, it will come up to it and hold there with only minor variations.
Click to expand...

If the higher temp is constant as you say, I would think that the cooling system is working properly. I think it would be good to know precisely what the higher temp is and compare that with your thermostat and, as much as possible, with the dash gauge.
I know the common wisdom is that it is never the thermostat but if the temperature measured on the engine is actually over what the thermostat calls for, and it holds steady at that temperature, it would seem to be worth the relatively the minimal expense and effort of changing it.
Tom
 
I really have no suggestions- if the temp. guage is not accurate but reading too high, then what changed since you got a normal reading initially?

I am also thinking the cooler reading on the exhaust manifold id odd- if carb related it should affect both cylinders supplied by that carb, if a head gasket or valve problem how is the compression so consistent?

I can only think some sort of debris has partially blocked the flow of coolant to the back three cylinders, but not number one. Is it possible that when you rebuilt the engine and rodded out the coolant passages that some loose material was left behind?

Otherwise I have no idea, but hope you will tell us when you solve this!
 
I'd be surprised if somehow something just now came loose. It was pretty darn clean when I rebuilt it and its been fine since august of last year and about 1100-1200 miles. I hate to just start tearing things apart on an engine that is running so well but I also don't want to run it until it self destructs either.
 
Since it seems to be reading constant, can you leave the radiator cap off, bring the car up to temperature and see how the actual temperature compares to what the gauge is reading? If the gauge is off then it's either sending unit, voltage regulator or the gauge.

Scott
 
SOLVED! The short story is that the thermostat was failing and I was measuring the manifold improperly.

The long version:

After tearing apart the entire cooling system including removing the pump and Tstat housing, I found no issues. I had checked the Tstat in water to ensure it was opening fully and it was. This is where I made the mistake, I did not have a thermostat in the water when I checked it so I did not know the temp of the water in the pan when the unit opened, I just knew it opened before boiling and it opened fully. Well after I have removed the pump and found no issue I decided to go and buy the $3.95 thermostat from FLAPS and replace it. I reinstalled everything and it operates perfectly.

To address the different manifold temp readings:
I had been using a laser reader on the manifold and the Tstat housing to determine temps. I had been checking the temps just after shutting the car down because I did not want it to stay idling too long given the poor cooling situation. This was my error. After solving the cooling problem I shut the car down in the garage and checked the manifold and Tstat housing temps, previously when the car was running very warm the housing was ~177 and the manifold was 390, 485, 490, 475. When measured after the cooling was repaired the housing measured 133 with a 160 Tstat installed, the manifold was slightly cooler all the way down. I restarted the car and found that when measure the manifold temp the closer to the head I got the cooler it was, I changed me measuring point slightly on the front outlet and received a "proper" reading of ~440 from all cylinders.

The take away, find the cheapest thing to repair and do it first! Also, measure temps with the car running, when you shut it down certain parts immediately bleed heat and other parts heat up quickly, to the tune of ~50 degrees on the manifold temps.
 
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