Engine runs hot

[d10s69c10]

seems to me somthing is a miss and if it doing this consistently it doesnt sound like you accidently got a reverse flow pump.. i agree with alot of above take a thermometer to it...


kinda like getting a royal flush but it is possible to get 2 bad units. ive had that problem with Motorcraft relays.

[Mr Chevorlet]

I would check your timing, i have had first hand experence with this on a 235 six cylinder and after all the thing you have done i did. and went to the distributor and sure enough adjusted the timing and problem gone.

[newbraunie]

Originally Posted by kcjones

Put 12v on the red prong of the voltmeter, touch the black prong to the body of the temp sending unit (not the connector!). You should show very little resistance. By moving the black prong of the meter to the connector, the resistance should shoot up if cold. If it only jumps a little while cold, your temp sensor isn't doing it's job: When cold the resistance of the sending unit should be high, when hot, resistance declines (no resistance, meaning a short, will shoot your guage up to 240+).

Guys, chime in here...that 6 cyl and stock radiator/"shroud" should keep this thing at about 180 idling in normal outside temperatures, right?

You shouldn't have to install a 4-core, shroud, and all that. There's something wrong with the reading, air flow, coolant flow, or ignition timing/carb mixture. You're on the right track, though.

Not sure if you meant to check resistance with ohmeter? (I do not have one) Anywways, with engine cold here are readings I have with voltmeter. Red prong on positive battery terminal, black to body of temp sender = 12.8 volts, black prong to connector = 9 volts. It appears that sending unit is well grounded?

[newbraunie]

Have run with timing from 0 to 4 degrees. Specs call for 0 degrees w/manual tranny but it runs better at 4 degrees. Neither setting had any affect on temp.

I am back from parts store with mechanical gauge. Figure this will solve the issue of whether or not engine is running hot.

[Mike J]

if you have access to an infrared thermometer, that helps out a lot- you can check the temp of the upper and lower hoses, different sections of the radiator, heater hoses, etc. while it's running and system is closed- and see if you're getting a big temp difference somewhere (restriction) and you can also see if the coolant temp is really as high as your gauge is reading...

[Slik69]

Originally Posted by Mr Chevorlet

I would check your timing, i have had first hand experence with this on a 235 six cylinder and after all the thing you have done i did. and went to the distributor and sure enough adjusted the timing and problem gone.

This was going to be my answer along with checking the heater core. Mine was leaking and I was driving myself crazy doing all sorts of unecessary changes. I learned that the heater core was bad.. so I bypassed it and have not had a problem since. That and the fact that timing was off. Is this a newer built or older motor with a lot of miles on it. I would still say timing if nothing else checks out for you.
Timing too retarded can cause to run hot too. I would get the timing dialed in.. and not pay too much attention to the guages.. if it's hot.. you will know it. Do you seem to lose a little power too when this is happening.

[newbraunie]

Installed mechanical temp gauge. Highest reading sitting on driveway - (can't drive truck since master cylinder cover off and along with other pb parts are off being plated....getting ready for pb conversion) is just under 210degrees. When I rev up engine it cools down to 190-195 degrees. I assume driving truck at 60 mph with more airflow through radiator it will run even cooler. I am playing around with the two (old and new) temp sending units. Have them tucked between lower rad & heater hose and alternating gauge comnnector between them (also grounded to battery) and they transmit identical readings although at low temp. I am relieved that engine is not overheating, OK with 190-195 degrees. I don't really want to install mechanical gauge as permanent so I may try another new sending unit with no thread sealant to rule that out. I also cannot find any wires grounding block to frame so I will take care of that. There is ground from valve cover to firewall and neg battery cable is bolted to cyl head. I am leaning towards conclusion that this is a grounding issue since replacing sending unit did not change gauge reading and old sending unit was installed with no thread sealant. Thanks to everyone for their tips and suggestions!

[Sport/Truck]

Originally Posted by newbraunie

Have run with timing from 0 to 4 degrees. Specs call for 0 degrees w/manual tranny but it runs better at 4 degrees. Neither setting had any affect on temp.

I am back from parts store with mechanical gauge. Figure this will solve the issue of whether or not engine is running hot.

Originally Posted by newbraunie

Installed mechanical temp gauge. Highest reading sitting on driveway - (can't drive truck since master cylinder cover off and along with other pb parts are off being plated....getting ready for pb conversion) is just under 210degrees. When I rev up engine it cools down to 190-195 degrees. I assume driving truck at 60 mph with more airflow through radiator it will run even cooler. I am playing around with the two (old and new) temp sending units. Have them tucked between lower rad & heater hose and alternating gauge comnnector between them (also grounded to battery) and they transmit identical readings although at low temp. I am relieved that engine is not overheating, OK with 190-195 degrees. I don't really want to install mechanical gauge as permanent so I may try another new sending unit with no thread sealant to rule that out. I also cannot find any wires grounding block to frame so I will take care of that. There is ground from valve cover to firewall and neg battery cable is bolted to cyl head. I am leaning towards conclusion that this is a grounding issue since replacing sending unit did not change gauge reading and old sending unit was installed with no thread sealant. Thanks to everyone for their tips and suggestions!

It sounds like your grounds are are probably ok, I don't care for using the valve cover bolts tho. Heres how I did mine.
s/t

[Slik69]

Originally Posted by newbraunie

Installed mechanical temp gauge. Highest reading sitting on driveway - (can't drive truck since master cylinder cover off and along with other pb parts are off being plated....getting ready for pb conversion) is just under 210degrees. When I rev up engine it cools down to 190-195 degrees. I assume driving truck at 60 mph with more airflow through radiator it will run even cooler. I am playing around with the two (old and new) temp sending units. Have them tucked between lower rad & heater hose and alternating gauge comnnector between them (also grounded to battery) and they transmit identical readings although at low temp. I am relieved that engine is not overheating, OK with 190-195 degrees. I don't really want to install mechanical gauge as permanent so I may try another new sending unit with no thread sealant to rule that out. I also cannot find any wires grounding block to frame so I will take care of that. There is ground from valve cover to firewall and neg battery cable is bolted to cyl head. I am leaning towards conclusion that this is a grounding issue since replacing sending unit did not change gauge reading and old sending unit was installed with no thread sealant. Thanks to everyone for their tips and suggestions!

Most cars (from my own experience) run a little warmer at idle than they do driving. I could give you several stories about this on several different cars I've owned. Driving the car spins the motor faster (fan) which keeps cooler. I must have missed that you were not driving the car somewhere in the thread. A classic car (pre computer stuff) will often sometimes always run a little hotter on idle.. not always though.

[Conroe trucker]

I have a 292 and 250, and also live about 150 miles from you.

The reason a six has no real fan shroud is it really does not need it.
It can almost cool itself off the heater.

I just had an issue with mine, the original 67 rad cap finally lost it's 7 lbs of spring. A 14lb. off the other one and I was down the road.

If the lifters do not start rattling it usually is not hot.
They usually will vapor lock way before then.

Now that it is cooler you should not have a problem.

[Tx Firefighter]

Question to answer is, does it overheat only at idle or going down the road ?

At idle = airflow issue, fan shroud, fan, etc...

At speed = coolant flow issue, radiator, pump, clog somewhere.

This applies to all liquid cooled cars.

[72BLUZ]

Originally Posted by newbraunie

Also, I went to back the raditor shop after putting radiator in. He performed test that detects exhaust gases in coolant. None detected. That should rule out head gasket leak. He recommended better fan since there is no shroud.

i work in a shop where we constantly trouble shoot that complaint. i have never heard of the test you say the radiator shop performed. what we do is take a 16 ounce coke bottle and fill half the bottle with water. then stick the radiator over flow tube in the bottle. let the engine run and watch the bottle. if it starts bubbling then you have a blowed head gasket. the best way to verify a faulty reading is with a ray gun. shoot the area around the thermostat housing and compare to the gauge and shoot around the temp sending unit and compare.

[68GMCCustom]

stock crank and water pump pulley?