Engine running hot

[FI Spyder]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Hasbeen</i>

Some time back, a few years, I had to fit a hotter thermostat in our winter, [Scottish summer by comparison], as the car was running just off the low stop on the gauge.
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Not a problem we are usually concerned about with the 7 as most people struggle with too hot, not too cold. A car will run cold if the thermostat fails as they are designed to fail open to prevent a car from overheating (which would happen if they failed closed). I don't know what would happen in a 7 but the thermostat failed in the Integra (was always open) during the winter (our winters here are like the winters in the south coast of Britain). The temp gauge barely moved off the bottom mark and there was zero heat from the heater. It's a big problem because to get at anything on an Integra you have remove six other things.

- - -TR7 Spider - - - 1978 Spitfire- - - - 1976 Spitfire - - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

[sheetsofsound]

The second thermostat I have that's not in the car says '195' on the top. For the thermostat that's in the car, the housing measures 160F once its up to operating temperature. Without opening things up again, I am assuming its a thermostat rated at @ 165F. The gauge in the car now never climbs much above 1/4. Generally, it sits midway between 1/4 and 1/2.

Is it bad for the car to run that cool? Or is it just an issue of not generating a lot of heat through the heater matrix for the cabin?

[John Clancy]

Nope, that's right.

Many of us in the past have made the mistake of removing the thermostat to check overheating issues, wrongly assuming coolant will run more freely without the thermostat in place but the reality is with these cars that the opposite happens. This is actually correct and how the cars were designed. Quarter on your temperature gauge is usually where the needle sits but I have had readings around a half with some temperature gauges.

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[Workshop Help]

As I conjure the Cosmic Conscience in the yesterdays coffee grounds and cross reference with the Crystal Ball, mystical spirits convey that the previous owner removed the factory 195 degree thermostat and went whole hog by installing a too cold rated 160 degree item. When will these people ever learn good things come with moderation?

A little history lesson first. Way back when, the factory installed for the emission equipped North American cars a 195 degree thermostat to increase the combustion chamber temperatures as a weak means of restoring lost power from using the 8:1 compression pistons. You see, the internal combustion engine is a heat machine. The heated combustion gases force the piston downward to rotate the crankshaft so the magic can be made. The more pressurized heat, the stronger the downward force. With high compression pistons the heated force is greater, so the 9.25:1 Home Market folks got about 109'ish horsepower while while the 8:1 folks got about 92'ish horsepower.

But there was a fly in the ointment. The design of the cylinder head and it's gasket are a bit thin on the ground in terms of strength. The 195 degree thermostat plus the combustion chamber temperatures combine to place the reliability of the sealing surface of the head right on the edge of failure. The other weak spot was the thermostat housing plastic/nylon filler plug which was prone to heat warpage resulting in a catastrophic failure as it would geyser the coolant to warp the already fragile head and gasket.

This is why the Big Recall occurred in early 1978 wherein the plastic/nylon filler plug was replaced with a metal plug and compression tests were made to ascertain the condition of the sealing condition of the head gasket. The dealers also very quietly replaced the 195 degree thermostat with a 180 degree item to reduce engine operating temperatures to preserve the head gasket, except in the colder climate areas where an extra hot heater was needed. Of note, around the same time, the factory changed the head gasket design to better seal the head to block joint.

180 degrees, this is the thermostat temperature rating you need, not the 160 degree. The engine needs heat to operate, and like the fable of Goldie Locks and the Three Bears, the porridge can't be too hot, (195 degrees), or too cold, (160 degrees), it needs to be just right, (180 degrees).

So, my friend, on your way home this evening, please stop by your favorite auto parts store and purchase a 180 degree thermostat with a new gasket. This will place your temperature gauge to read just about a needles width to the left of the center mark on the gauge. All will then be tranquil with the Mystical Forces of the Cosmos.

Mildred Hargis

[sheetsofsound]

Thank you for the history on this point, Mildred. The Cosmos is still playing tricks with me, I fear. Perhaps I will achieve Cosmic peace once I accept that, while my knowledge may have its limits, my ignorance knows no bounds.

I stopped and got a 180F thermostat and proceeded to the garage with trembling hands. I removed the thermostat housing and extracted the thermostat, and what to my wondering eyes should appear but a miniature 180F marking on the top of the thing.

Only slightly daunted, I swapped in the new one and consoled myself with the thought that the one I just pulled out might be defective and opening early. Started up the car and headed off on a brief run to get some gas. Temp gauge was showing between 1/4 and 1/2, same as before. Once back in the garage, I took some quick readings with my trusty infrared temp sensor. Thermostat housing was reading as before - @165F. The head and block were reading between 170F and 175F, also same as before.

I don't know yet if the heater is throwing a decent amount of heat as I haven't reconnected my heater matrix; I have a rebuilt one and will be swapping it in once I get some new dash bulbs. (Going to do the whole business at once while the dash is out.)

Anyway, I guess I need to get used to the new normal temp reading between 1/4 and 1/2. Perhaps the new temp sensor is acting a little shy?

As an aside, I have devised a diverter to reroute coolant away from the heater core. I have become quite addicted to having unheated ambient air blowing through the vents when its warm out. If people are interested I will photograph the build and post the mod if it works. The diverter valve is out of sight on the transmission tunnel and is easily reachable from the driver's seat. All the parts to build it cost me less than $25.

[John Clancy]

The gauge reading you have is correct so don't worry about it. All cars vary a little but just over a quarter is the most common reading but anywhere up to half is fairly prevalent.

Enjoy driving your car.

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