Question: RUNNING TOO COOL

[BLK VERT]

Hi, I have a question to ask. I just got my rebuilt motor in the vett and running. It's been close to a year since it's been down. The problem I'm having is that the motor runs cool. Around 150 degrees. I changed the thermostat twice. ( 180 ) and it's the same. On my stock gauge the neddle is in between the 100 and the first hash mark. I believe the first hash mark is around 155 degrees Is that correct?
Where is other member neddle sitting when it warmed up?
I've used an infrared temp gauge and a temp with the long neddle to put in the water. The closest I can get is 160 degrees. People are having trouble trying to bring their temp down, and I'm trying to get it up. I'm stumped. Can anyone help? Tony

 

[Gry Ghst]

Welcome!!!Can't solve problem but the cooler the better,cold=HP!!!

 

[warren s]

Tony

Is this after some driving around or just sitting at idle for a few minutes? Are you running a clutch fan or a flex fan? Did you also change the radiator to a larger capacity one? Even if the thermostat was stuck open I would bet that it should run hotter.

Is it a stock rebuild?

 

[XLR8]

Welcome to the Tony!!

You've come to the right place for all things Corvette! The members here are knowledgeable and more than willing to share their experiences.

Good luck with your '69 and post photos when you are able. We'd love to see it!

Jane Ann

 

[KANE]

I have an aluminum radiator, a 180 thermostat, and the factory style fan.

The only time the gauge moves close to 200 is when these four conditions are met-

1. in drive
2. at a long stop light
3. in 95 degree weather
4. more than 30% humidity

It doesn't crest 200... it just gets close to the hash mark. Otherwise, it sits on the middle hash mark when I'm driving. I take what the gauge says only as an anecdotal reference.

On my last C3, I replaced the fan clutch. It made a huge difference. If the fan clutch is stuck or not otherwise operating correctly... you'll run too hot or possibly too cold. Couple that with the wrong thermostat and it will appear to run very cold.

 

[BLK VERT]

Thanks guy for the Warm well. I had the stock 350/350 rebuilt. What I had done was: flat top forged pistons, roller tip rockers, hyd roller lifters, cam id just alitter hoter than the LT1 cam, recored radiator, and it the stock clutch fan, 5sp trans, and the themp is when I ran the vette on the hwy or the streets. Yesturday was HOT! Igot warmer readind after getting off the freeway. But it was around 160- 170. but for the most part it runs aroun 150.
DarkShark, up the middle means 12:00 ? And if mine is between the 100 and the first hash, it under 150? Tony

 

[JohnZ]

Where did you "shoot" when you took the I.R. gun reading? That should be done on the upper radiator hose, just above the thermostat housing, to get an accurate reading. If you took the thermometer reading by sticking it in the expansion tank (or the radiator filler neck), both of those locations are on the COOL side of the radiator, not the (hot) engine exit side.

 

[BLK VERT]

Engine exit is the themostat housing right? I shot the IR on the upper and lower hoses the small hoses to the manifold and the water pump, the sending unit , the left and right heads, the radiator. I'm going to see if I can get a mech. temp gauge and hook it up on the pass side head. That might give me a better reading I hope. I've been shooting the IR so much, I have numbers writen all over the place. Just checked the paper I had the wife write on and got some high numbers when I was driving in the 80-90 weather yesturday. The upper rad. hose was around 175, the lower hose 155-160 . Funny thing is the gauge neddle just goes between the 100 and the next hash mark. Moving alittle back and forth between. Could the gauge be bad ot the sending unit in the head. Someone said the sending unit must match the gauge?

 

[JohnZ]

The upper rad. hose was around 175, the lower hose 155-160 . Funny thing is the gauge neddle just goes between the 100 and the next hash mark. Moving alittle back and forth between. Could the gauge be bad ot the sending unit in the head. Someone said the sending unit must match the gauge?

I.R. readings look normal. To check the gauge - disconnect the wire at the sending unit, and the gauge should peg to full cold; then ground the end of the wire to the engine and the gauge should peg to full hot. If that checks out, the sending unit is bad; if it doesn't, the gauge is bad.

 

[BLK VERT]

Thanks JonhZ for the tip. I'll do that tonite. Every little tip helps me. Tony. I went and bought some antifreeze, distilled water, and a mechanical temp gauge. Plan to put the gauge on the passenger side of the head. When I can get around to it. This is another way for me to know. since the mechanical gauge has numbers that I can read. Seems there's a difference of opinionabout the correct sending unit on the 69. Some say the pointed tip and the other is the flat top. I have the flat top. Which one it the correct one? My green wire holds the flat top. Thanks, Tony

 

[Vette79]

I would bet it is the Temperature Sending Unit. If it is not the correct Temp Sending Unit with the correct ohm rating for your guage then it will report an incorrect temperature. The lower the ohm rating for the unit the lower the temperature reporting on the guage. I did a top-end rebuild including different cylinder heads which meant a different temp sender. IR gun was reporting 180* while the guage was at 240*.

 

[minifridge1138]

What brand of 180 thermostat are you using?
I've tried 3 different Mr. Gasket 180 thermostats and they all ran at about 150. There are a few other people on here that have had the same problem with the 180's. I've had no problem with their 160 thermostats, they actually ran warmer than the 180.

 

[BLK VERT]

Update: I went out and bought a mechanical temp gauge and hooked it up on the passenger side head. First, I need to clarify the reading on the stock 69 gauge.On the stock gauge, my needle is between the 100 an the first hash mark when it's warmed up. I've been trying to get someone to tell me what is the temp reading but got many different opinion. From the 100, the next line has no number and I'm assuming that it's around 155*. Is that correct? If that is the case, then the motor is running under 150*. The motor is then running too cool. Anyone out there has the same stock gauge and where does your needle sit when it's warmed up? On the mechanical temp gauge, it's 130* then there's three more line to 190* so 4 lines and the needle is on the third line which means 170* ( incredments of 20*) the needle is pointing at around 170* Right? So the motor is not running cool as I was basing the stock gauge as running under 155*. So Let me know where your stock gauge needle is pointing at. And Am I correct in assuming that the second hash mark is around 155*? Where is 180* on the stock gauge? Sorry for this confusing post. This is driving me batty too. Tony

 

[Bolisk]

I'm afraid that I can't be of much help. . .other than to tell you that I have the EXACT same problem. My 1970 runs dead smack between the 100 and 155 hash mark. I have a 5 blade "correct" fan with clutch, a Copper radiator, and have tried 2 180 Mr. Gasket thermostats. I've replaced the sending unit and have verified that the gauge is functioning. I finally took the car on a very demanding drive in 90 degree weather, and really got the engine going. My car just kept right between 100 and 155. The only time it ever got to 155 was sitting at a long stop light.

I've had the car looked at by three shops, and they have all agreeded (using IR guns) that my car runs at 130 degrees. No one seems to be able to explain this to me. Normally I wouldn't complain, except that I have read stories about how engines that run cold 160 degree or below, wear at a rate two to three times faster than an engine running at 180.

Now, the ONLY thing that is not stock to my car's engine, which could be contributing to the cooler temps, is that I'm running a Hight Flow / High pressure (70psi) oil pump. In theory, the higher flow could be helping to cool the engine more. . .but I'm also at a loss.

-Bolisk

 

[BLK VERT]

Hey Bolisk, Yeh this has been intresting. Been asking the same question in another corvette forum and some say the hash mark is not 155* but maybe close to 180*. I recieved my new sending unit from Dr. Rebuild and installed it. Took it for a run and the stock gauge went up a little pass 210* while the mechanical gauge is around 170*. I've been told that the original sending might be hard to replace. On your sending unit, what type on end do you have? Flat or the thin tip? Funny thing is that I have the flat top, but the flat top in the Willcox inc web site shows that it's for vettes from 58-67 and the needle type is for 68-71. So I'm wondering if I have the wrong year sending unit or did the 69 also come with the flat top. It's says to check the sending unit with an ohm meter. Tony

 

[Bolisk]

I have the correct temp sending unit (needle tip) and wire loom. Both are "correctly" calibrated. I bought both from Lectric Limited.

Now, having said that, I'm aware that the sending unit and gauges can get out of wack over time, and that there is really no guarentee that they are both calibrated together. This is why you always use the IR gun to mesure temp. If the IR gun says that you are running 180, and the gauge says that you are running 160, then you need to put a resistor (or something) on the gauge to correct for the mis-read. This is a common issues.

My problem is that my car actually runs at 130 (confirmed via IR gun). And that is after hours of hard driving.

Oh yeah. . .one other thing. I don't have my heater core hooked up. I have a hose looped from the water pump to the intake manifold. Note: This is NOT bypassing the thermostat.

-Bolisk

 

[JohnZ]

My problem is that my car actually runs at 130 (confirmed via IR gun). And that is after hours of hard driving. -Bolisk

That's not possible - the thermostat won't allow it to run below the thermostat's rating point. The I.R. gun shot has to be taken on the radiator hose, just above the thermostat housing outlet (a matte surface); if the shot is taken on the housing itself, the glossy surface will distort the reading due to emissivity.

 

[Evolution1980]

So educate me...I know things like auto-trans and whatnot need to get up to operating temp, but what's the problem with coolant running "too cool"?

 

[Bolisk]

The IR gun was done at the thermostat housing and the hose conneted to the thermostat housing. I've gone to three shops. . .three seperate IR guns. . .three seperate people. I'm agreeing with you. . .it's not possible. . .but there it is.

So I read an article in Corvette Enthusiest about how the rings and bearing wear faster if the engine isn't up to op temp. . .somthing about tollerances and such. . .

I read that a LONG time ago. I may be wrong.

 

[BLK VERT]

I've heard the same thing about the wear or the longivity of the motor if the temp is too low.That's one of the reason for trying to bring the temp up. So Bolisk, what does your wire end look like? The one that connects to the rod type sender. Can the temperature wire lead fit both the thumb tack style and the rod style? Should I be running the rod like sender? Tony