New 427 pegged at max temperature. HELP!!

[cwilkie]

Just got my 427bb installed. Runs great except that runs way too hot. Thought it was a bad temperature gauge on the dash cluster but after changing it the gauge was pegged at the max. Next I am thinking it is a bad temperature sender or thermostat. After that I will move onto the (short) water pump. The radiator was brought in to be cleaned up and restored so I do not think It is that.

What are your thoughts? Anyone have any advice? The short water pump was purchased from O'reilley's auto parts. So I do not know what quality their parts are...
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[slow72pckup]

Posted in classifieds but have you checked to see if thermostat is opening
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[HotRod C/10]

pull the thermostat and try it again

[71swb4x4]

I would hook an aftermarket gauge up and use that as well as the factory gauge.
Make sure your fan shroud is installed.
Then I would drain the coolant and refill it carefully making sure there aren't any air pockets. While the coolant is out test the thermostat in a pot of water on the stove to make sure it is opening.

[71swb4x4]

I wouldn't run it without the thermostat. Many people say that without the thermostat the water moves too quickly through the radiator and does not get properly cooled. The system needs the restriction of the thermostat.

[cwilkie]

So remove the thermostat and let it run for a while and see if their is a difference in temperature? I have a standard temp thermostat installed now but I will try that tomorrow. Thanks!
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[GASoline71]

I wouldn't pull the T-stat... but that's me.

Leave it in, and get a sending unit and gauge that are known to work and hook them up. Or find someone with an infared heat reader. That will tell you if it's too hot.

If an engine gets over 260... it'll start to even smell hot.

Gary

[Psycho71]

I'd start with an aftermarket gauge and see what it reads.

Instead of pulling the old stat completely out, take it out and use a pair if wire cutters to take the center out of it. The you'll have a big washer with a hole in it that will slow the water flow through the cooling system. but if you are going through all of that, just put a new stat in it.

[HeavyMetalChevy]

heads....or gasket... check compression on all cylinders. sometimes starting big is a better way to narrow down to smaller problems. If you have all cylinders with proper compression and you run across two next to one another that drop.. Great way to tell if there is lost compression and hence overheating with cracked head gasket.

[cdowns]

i'd check the actual temp of the coolant with a known good thermometer first b4 changing and swappin things out in a random kneejerk reaction

knowing what u are actually dealing with prior to changing parts i find helps in solving the problem if in fact there is a problem

[cwilkie]

I tried a known working gauge. Next up is a different temPerature sensor. I will keep you posted.
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[Fesser]

I'll probably get reamed by the safety police but... start it cold without the radiator cap on and after a bit you should easily see the coolant start flowing when the thermostat opens. Obviously be careful and don't let it get so hot that you get a geyser. This won't tell you why it is running hot but will at least let you know if the t-stat is stuck closed. I also agree with those saying to check with a different temp guage and sender even if it is hooked up temporarily under the hood.

[cdowns]

Originally Posted by cwilkie

I tried a known working gauge. Next up is a different temPerature sensor. I will keep you posted.
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not the same as a KNOWN GOOD THERMOMETER// you end up as just a parts changer your way

[cwilkie]

Could it be the temperature sensor is in the driver side head right above the exhaust manifold? On my other big block truck the temperature sensor is mounted in the intake near the water outlet. It is hotter near the exhaust manifold isn't it?... Scratch that. The intake does not have a place to mount the temperature sensor.
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[truckdude239]

yes the exhuast can cause the sender to read wrong

[cwilkie]

Is there a heat shield that I could put on the temperature sender?
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[butch86]

just a thought but do you have the fan installed correctly and is your can clutch working?

[oldblue1968chevy]

i had same problem, timing was way off

[7dee2]

All good suggestions.

Check your oil for signs of water. Whip cream is bad and could be a lot of different problems. If you do have water in the oil you have to find where it is coming from.

Re-verify your timing. Probably not your problem if it is starting, running and shutting off well. But could not hurt to rule it out.

Put a paper towel in front of the radiator to verify you installed the fan correctly. Should have enough pull to keep it there. If not you may have installed your fan backwards. Make sure it is pulling air and not pushing it.

I would move the temp. sender get a thermostat housing that will accept a temp. sender. Also put your thermostat in a pot of water on the stove. Bring to a boil and make sure it opens. If you have a thermometer you can verify it opens at correct temp.

Once you reinstall the thermostat you should feel the upper house get warm once it opens. You could also leave the radiator cap off and look for good coolant flow and radiator is not plugged.

I doubt you have a reverse flow water pump but that could cause a big problem as well.

If all this fails I would look to who ever built the engine. If something internal is wrong it will create a lot of heat. If this is the case it would need to be torn down to find the problem.

Saw this not long ago with a BBC 427 Corvette restoration engine, cam would walk forward and push the timing chain into it's cover. Hand held temp gauge found the problem quickly and a cam button solved the problem.

Good luck.

[WTexChevy]

You did use the correct sender to the vehicle right? Probably a dumb question but I've done it before...

[cwilkie]

Great suggestions guys. I will keep you all posted. Thank you again!
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[storm9c1]

Does the gauge peg immediately when you start the truck cold or does it slowly climb over a minute or two? If it pegs immediately, it's an electrical problem (sender wrong or bad or wire shorted to ground).

If you have a Harbor Freight nearby, you can get an infrared thermometer pretty cheap there. I couldn't live without mine since you always needs a good sane temp reference when debugging problems like this.

[cwilkie]

Relief!!! It appears it was the sensor being mounted next to the exhaust manifold. I bought a new water outlet housing that had a thread hole for a temperature sensor. I got a separate temperature sensor and mounted it in the water outlet. I then let the truck warm up until the top radiator hose got warm and then look at the gauge. It was running just above the "C". To be sure I removed the temp wire and mounted it in the original temperature sender still in the exhaust manifold. The temperature gauge skyrocketed to "H". I placed the wire back on the new temp sender mounted in the water outlet and it was running at a normal temp. It must have been the exhaust heat giving me an inaccurate reading. Thank you guys for all the suggestions.
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[7dee2]

Congrats!! Glad you solved your issue..

[GASoline71]

Sure the timing isn't retarded too much? Retarded timing will cause the exhaust to be hotter. Sometimes even having a manifold or header glowing red.

Mounting the sender in the head is the stock location, and I've never had a sender prob with it mounted in the stock location.

Gary