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Wedge Uh-oh: TR7 Pegging HOT on temp gauge!

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sammyb

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I was out trying to improve the idle a few weeks ago, and I thought the temp gauge started freaking out, because I looked in and it was all the way hot.

Last week I tried again and watched the temp gauge spike quickly to hot.

I replaced the thermostat today, still doing it...but I noticed not a lot of coolant in the neck -- so I'm thinking either the water pump is shot, or the dreaded head gasket.

I'm leaning towards water pump, since it had no troubles the last time I drove it a few weeks ago.
 
check your grounds...i had a similar problem and it was a ground wire under the dash...i can't remember what exactly it was i will find out though
 
>>I was out trying to improve the idle a few weeks ago

If it was getting hot at idle, this is not that surprising -- as long as it cooled right off when driving normally.

If so, I'd think the water pump seals are getting weak and the pump isn't efficient at low revs. It could also be a partially blocked radiator. If it's a 76/77 it's the nature of the 6 vane pump itself. Later cars used 12-vane. You're right -- it may be due for a new pump.

The dreaded head gasket would be blowing coolant out the top of the bottle. If it were the ground, then I'd expect the temp gauge to be hot all the time. BTW -- the temp gauges do go bad as do the temp sensors. But if it's idle-only then I doubt it's these last items.
 
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check your grounds...i had a similar problem and it was a ground wire under the dash...i can't remember what exactly it was i will find out though

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When you filled the bottle and then tried it, when it got hot did it start sending coolant out the overflow? If not, then a bad sensor or ground may be the best explanation; it's not really getting that hot. When I took mine in for safety and emissions, the shop had it idling for over 15 minutes with the bonnet open. The temp got up to just over 3/4 when it started overflowing. Closed the bonnet to get airflow going thru the radiator, and it immediately cooled back down to just under 1/2 way (it's normal spot). So if you're not getting overflow when the bottle is full and the gauge is showing HOT, then it may not REALLY be hot.

Unless you have an electric fan, and it really is hot, check the fan clutch to see if it is actually working. If not, it won't pull enough air thru the radiator.
 
Sammy, have you checked your temp gauge? I've seen more than one temp gauge go haywire. BEfore you dig into the engine, test your gauge.

I learned this the hard way on a GT6. Actually, it's possibly the best news you can receive regarding "overheating". Gauges are cheaper than cooling systems!

Good luck!
 
I had a temp sending unit go bad on my rangie. It would indicate a temperature about 50 degrees or so above the actual temperature. I had thought they would be good or all bad, not half bad.
 
check the cheap stuff first...temp guage sending unit, thermostat, then move on to waterpumps, clogged radiators. It could be a sending unit, especially if nothing is boiling over, and the gauge still reads hot. When the sending unit goes, you get all kinds of queer readings.
 
Sammy,

A quick and easy way to check your temperature gauge is with a candy thermometer. Just place it in the open radiator and compare the temperature of the coolant (based on the candy thermometer) to the gauge reading as you warm up the engine.
 
The Voltage stabalizer has to be grounded, in order for the temp gauge and fuel gauge, to work properly other wise the both read all the way to the right (max)

edit: i found this out on my 73 TR6
 
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Just be sure to wipe it off with a rag before you put it back in the kitchen drawer.

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Are your suggesting that I might be sneaking my wife's candy thermometer out to the garage Geo? No way! This is *my* thermometer. If the Mrs. wants to use it to actually "make candy" (or whatever you really do with a candy thermometer), she'd better make sure *she* wipes it off before returning it to my tool box. <grin>
 
I had the same problem last year, new thermostat and temp sending unit, both cheap parts, and the problem was solved. I figured this was the problem because the car was not overflowing any fluid. I think I was lucky.
 
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