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TR2/3/3A overheating tr-3

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Hi Guys,

Thanks for all the help with this overheating or whatever it is. Ok, this is what I did tonight, put in a 60 degree C thermastat, I have the bypass plugged with a 3/4 copper pipe cap with a 3/16 inch hole drilled in it. Also the thermastat has a tiny relief valve to eliminate an airlock. I still have the old cap 4lbs, new one on order from moss, 7lbs for tr-4 long neck rad. The car is a 57 but has a tr-4 engine and drivetrain. the qauge reads in Celsius and maxs out at 100C I did not know about the Voltage stabilizer, I have to find the old link and see if I can make one. The car did have the mechanical temp guage but it was long gone when I got the car. Anyway, the engine will idle fine at a little over 70C but as soon as rpms are increased the temp gauge maxes out and the rad cap pops open and bleeds off some water. I checked the thermastat housing temp with IR thermometer ($16.99 at harbor) temp read 63C, then 71C, then 80C, the head readings were 78, then 80 and 90 before I shut it down. I guess I need to put the new rad cap on and try it again. I added Baking soda and let it get hot again, opened block drain, had to poke coathanger in the hole to get it flowing but claer water came out, the radiator drain valve was clear and the water was clen. Checked the hose from the rad to the water pump, it's clear.
 
Hate to say it, but it's starting to sound a lot like you have a leaking headgasket or similar. How quickly is "as soon as"? If we are talking seconds rather than minutes then I think you must have a compression leak into the water jacket.

New voltage stabilizers are available from the usual suspects if you don't feel like building your own. The originals are not polarity sensitive, but the solid-state replacements generally are (Moss sells two different part numbers for either positive or negative ground).
 
Hi,
I looked at your old posts regarding the voltage stabilizer, as rpms increase the temp gauge gets pegged, I suspect my problem is running the tr-4 temp gauge without the voltage stabilizer. I will check to see if the VR is in the circuit or not.
Thanks Again,
Captainde
 
Hi,

I used the wrong term (as soon as) I ran the motor for a good ten minutes, idling and a quick spin up and down the street. when I cam back I let it idle, The engine also gave me the impression that it was loading up at idle and ran rough until I goosed the throttle. I shut it off and that's when the rad cap popped. (4lbs) Hope I don't have a head gasket problem but it's possible, The engine from what I am told was rebuilt before the prior owner bought it and he put very little hours on it, I would like to believe that the head gasket is still good, would that leak show up on a compression check?
Thanks,
captainde
 
Quite possibly.

Other possible clues would be the sweet smell of coolant in the exhaust or bubbles in the coolant when you're (carefully) looking into the radiator neck.

The radiator will puke if there is too much coolant in the system... on a TR3 just enough to have about a 1/4" or so in the bottom of the neck is about right. Much more than that and it will be coming out the overflow tube as the coolant expands.
 
It's not unusual for a compression leak to be small enough that it won't show up in a compression check. I had that problem for many months with my TR3A, it would be fine running 'around town' but boil almost instantly when I got on the freeway. The definitive test is a "block tester" that will check for CO2 (combustion gases) in the coolant. You can buy the tool yourself (I found a used one on eBay for $25) or your local radiator shop should be able to do it for you (mine charges $18 for the test).
https://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm

But your last description sounds less like a compression leak, so I would investigate other avenues first. As Geo notes, the radiator should not be filled to the top, otherwise normal expansion of the water will force it out the cap.
 
TR3driver said:
...The definitive test is a "block tester" that will check for CO2 (combustion gases) in the coolant...
Click to expand...

As an alternative to sophisticated sniffing of the coolant, I did a home-made test to check for (and found) this problem in a non-TR (Fiat actually).

With the overflow tube plugged or clamped off, I stretched a latex 'item' obtained from my local pharmacy over the neck of the radiator. As the engine idled the 'item' quickly inflated -- quite exciting.

I suppose a rubber glove would also work, not as dramatic but it might give you a friendly wave as it inflated.

But really Cap'n, this experiment probably not necessary in your case.
 
Geo Hahn said:
TR3driver said:
...The definitive test is a "block tester" that will check for CO2 (combustion gases) in the coolant...
Click to expand...

With the overflow tube plugged or clamped off, I stretched a latex 'item' obtained from my local pharmacy over the neck of the radiator. As the engine idled the 'item' quickly inflated -- quite exciting.

I suppose a rubber glove would also work, not as dramatic but it might give you a friendly wave as it inflated.
Click to expand...

Help me here Geo - not sure what product you are talking about...
 
tdskip said:
Help me here Geo - not sure what product you are talking about...
Click to expand...
Hint : "Sold for the prevention of disease only"

Another old-timers test is to remove the fan belt & thermostat housing, then fill the system up to the top of the head. Start the engine and 'goose' the throttle several times; if you see bubbles rising (obviously before the engine gets hot enough to boil), you've got a leak.
 
TR3driver said:
...Hint : "Sold for the prevention of disease only"
Click to expand...

Quite. Also available in many gas station restrooms in colors and the glow-in-the-dark variety. Now that conjurs up some possiblities.
 
Isn't anyone going to come up with the old chestnut about shower apparel?
 
Thanks for all the ideas and new uses for those items in my medicine cabinet, I bought a voltage regulator at my local electronics stor, a 7810 and will install it next week, since I have a positive ground tr-3, I'm wondering how to connect it, should I connect the Instument terminal to the neg hot side of temp gauge and the bat term of the VR to the neg hot side of the wire that was connected to the temp gauge? And should I insulate the ground lug of the VR from the chassis?

Thanks,
captainde
 
You have an email from me on this. In short if you use a 79XX rather then a 78XX then you don't have to worry about insulating the tab and running it all in reverse.

BTW, I used a 7912 as my test of the sender to characterize temperature versus resistance worked out that 12V was closer to reality then 10. The mechanical regulator that came with the car was an on off thing the "sumulated" a voltage (I think) so the value you would get from reading the output of that would be dependant on what you read it with, and if the gauge is different then the meter you used then ... you see where this is going. I hope I did not just kick up a hornets nest.
 
Adrio said:
The mechanical regulator that came with the car was an on off thing the "sumulated" a voltage (I think) so the value you would get from reading the output of that would be dependant on what you read it with, and if the gauge is different then the meter you used then ... you see where this is going. I hope I did not just kick up a hornets nest.
Click to expand...
No argument from me; the original "voltage stabilizer" switched very slowly and any ordinary test meter is going to follow it's switching between 0v and full battery voltage. In fact, the quick test I recommend is to connect a test lamp across the sender, and watch to see if it blinks on and off.

The Lucas-recommended accuracy test is to use one of the gauges; calibrated with a resistor against a 10v lab supply.

Lots of things affect 'reality' as you call it, including the calibration of the gauge and the matching of the sender. There were originally a lot of different senders with slightly different resistance curves, which it seems the vendors have consolidated all into a "one size fits none" part.

But since the system voltage can easily drop below 12v under fairly normal conditions (waiting at a stop light at night with your foot on the brake, for example); and solid-state linear regulators can't output a voltage as high as their input (there is always some minimum difference, known as "drop-out voltage"); I wouldn't suggest using 12v instead of 10v. For example, an LM7912 has a drop-out voltage of 1.1 volts, which means that it must get at least 13.1 volts as input, or you won't get 12v out of it. The LM7810 isn't much better, as it's dropout voltage is 2.0 volts.

Here's the factory instructions for gauge testing, might be helpful.

https://i258.photobucket.com/albums/hh260...pg?t=1246077291

https://i258.photobucket.com/albums/hh260...pg?t=1246077554
 
Thanks Adrio,
I did not get your e-mail yet, so I should get a 7912 or 7910 VR? I'll get the right one next week, just let me know which one.
Thanks,
captainde
 
captainde said:
Thanks Adrio,
I did not get your e-mail yet, so I should get a 7912 or 7910 VR? I'll get the right one next week, just let me know which one.
Thanks,
captainde
Click to expand...

Depends on the voltage you want. Randall is right about the drop out voltage so from that perspective the 7910 is the right one. I used a 7912 because I knew exactly what my sender resistance vs. temperature curve was as well as my meter position vs. current curve was (from my little lab test) so I went with the voltage that gave me a more accurate temperature reading. However your millage may vary, as I may have had two components that were at the extreme of tolerance adding up to my need for 12v. In fact at idle with lights on and foot on brake I may not be able to sustain 12v at the gauge and have a lower reading then actual temperature (but then when are we ever stopped in these machines :smile: )

Let me know if you got my email.
A
 
Just a thought; now might be the time to switch to negative ground. It tends to simplify anything involving electronics (like adding a CB or stereo) and the only downside is lack of originality. That would let you use your 7810.
 
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