REBUILT ENGINE START-UP......RUNNING HOT

[bluemiata90]

I know that this basic issue has been addressed before, but if you could bare with me. I just rebuilt my TR3 engine, refurbished radiator, pertronix ignition, etc. I did all the first start-up procedures before starting it. I had to use a TR4 temp gauge with the electric sending unit. The gauge reads up to 100 on the face dial.
The engine started right up, ran good, with several minor issues. The temp guage slowly moved up to around 100 and then the thermo. opened, it moved back down to about 80 and ran at that temp for about 5 minutes. Then within 10 seconds it went from 80 up to and passed 100. I shut the engine down and that's where I'm at.
The radiator is full, I installed a pusher fan in the front and it was working fine, Would the TR4 guage and sending unit work differently?. Any suggestions????.
The engine never overheated, it seemed to run fine, The radiator cap is old, but appears to be working.
HELP,HELP

 

[mrv8q]

Hello, Blue, others will chime in here, but I think I'd confirm first that the car is actually running hot.... You might test it w/ an infrared temperature gun. That way you'll know exactly what the temp at the housing is.... Good luck!

 

[Mickey Richaud]

Yep, might be a bad gauge and/or sending unit.

 

[TR3driver]

Did you install a "voltage stabilizer" for the gauge? If not, it will definitely read high.

 

[bluemiata90]

That's what great about this site, Great help. I'm on my way out to pick up a thermo gun and Nope, I didn't use a voltage stabilizer. I only hope that it's something like you guys suggested. Just a little update, after I let it cool down, I restarted it and let it run for about 15 minutes and the temp gauage went up to around 70 and never really moved from there. The oil guage went to 70psi and then settled in around 50psi. I never really noticed any antifreeze overflowing and the system seemed to be circulating fine. I'll cross my fingers. Thanks for the suggestions.

 

[DNK]

Just might have needed to be burped!

 

[philman]

i had a bad thermostat (brand new) installed in my TR8 when I brought it back from a long time sleep.

 

[bluemiata90]

DNK may have hit the nail on the head. I opened the radiator and topped it off and restarted it. I only had about 15 minutes to test it and it stayed within a respectible range. Over the next couple of days, I will continue to run and test it. At this point I consider the engine rebuild a success. Since I'm hoping the engine is finished, it's time to start on the body. I hope to be able to paint this TR3 in the spring. I also have a TR8 4 barrel conversion to complete before the spring. To many projects,not enough time. Thanks again to everyone for your input.

 

[DNK]

Well , I'll take the P1800 off your hands if it will help

 

[Roger]

I expect you got a bit of overheated steam from a pocket, and it sent the gauge all over the place.
That's happened often to me - nothing to worry about.

 

[dklawson]

Before leaving the topic, Randall's point about the voltage stabilizer is important. I'm not sure what year TRs added the stabilizer to the gauge systems, for BMC it was late 1964. If you have a gauge with rapid, bouncy needle response/movement it's typically the early type and doesn't use the stabilizer. The later bimetallic gauges have needles that move slowly and while they'll vibrate a bit, they don't bounce. Those gauges must have the voltage stabilizer. Without it, a working charging system can supply the gauge 14V or more (instead of 10V). As a result, the gauge can read quite a bit higher than it should AND you'll shorten the life of the gauge.

I don't know of a definitive site about the later gauge systems. The best site for information about the early gauge system (without the stabilizer) is Barney Gaylord's MGA-Guru web site.
https://www.mgaguru.com/

 

[bluemiata90]

In regards to the temp gauge and volt stabilizer. I have a 1961 TR3, but for the startup process I'm using a temp gauge from a TR4, year unknown. I installed the temp sending unit with the elecric hookup on it. At this time, I don't even know if I'm going to use this guage in the car once the body is back on. I will assume that since the guage seems to be holding steady at this time, that the stabilizer is not needed and since the engine is just mounted to the frame, the only electric hooked up is whats needed to get the engine broken in. Once I get the body back on and the new wiring harness in, I'll maybe start looking for the correct style gauge (since my original guage is trashed). I'll also have to take into consideration that the car is now neg. ground.(high torque starter,GM alt.,etc)

 

[TR3driver]

"stabilizer" is something of a misnomer ... the problem is that the gauge is designed to operate on 10 volts. If supplied with the 12-14 volts in the car's electrical system, it will read 20-40% high. For the TR series, all the electrical temperature gauges required voltage stabilizers (which means the beginning of TR4 onwards).

Original stabilizers (and the original gauges) do not care about polarity, but the aftermarket solid-state stabilizers do care. I don't know of any practical way to convert them, just buy the positive ground version if that's what you need (TR4 was positive ground, TR4A and later were negative).

To avoid the 'burping' problem, I like to drill a small hole through the thermostat backing plate (1/8 or 3/16). Install the thermostat with the hole at the top, so any air trapped inside the head can find it's way out. Better thermostats may already have a hole with a 'diddle pin' in it, so no need to add a hole to those (but it should still go at the top).

 

[Gliderman8]

I did away with the mechanical voltage stabilizer with my recently rebuilt engine (TR6). Instead, I used a solid state device that puts out a steady 10 volts for the gauges.
I did moniter the output with my VOM when I hooked it up, and it is 10 volts right on the head.
I think this is just a case of modern technology catching up with our cars.
Gliderman8

 

[NickMorgan]

Scott,
I am glad that your engine seems to be running at the correct temperature now. I am sure that the others managed to diagnose the problem and an air lock seems quite likely on a rebuilt engine.
I would imagine, also that a newly rebuilt engine is likely to run a bit hotter than normal on its first start. Everything must be a little tighter than normal and there will be more friction until things have worn in. Am I right with that thought?
Nick
(My engine ran hotter the first time I started it, but that was because the thermostat gasket hadn't seated properly and the coolant leaked out!!)