• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Hemi overheating....maybe

dammstrate

Well-Known Member
Local time
12:05 PM
Joined
Nov 26, 2019
Messages
106
Reaction score
71
Location
Eagan, MN
66 Tribute Coronet with 472 World block Hemi. Ed heads, intake, and carbs. I hadn't noticed before, but the temp gauge starts just above the "C" when I first start, and gradually goes to about 85-90% towards the "H" and then sits there, no further change no matter how far I drive (up to about 50 miles at a gime so far). No leaking coolant. Seemingly no issues. No steam from anywhere. 1 - how to tell if the gauge is calibrated? 2 - Can it get "too hot" and cauge damage without no observable signs?
 
66 Tribute Coronet with 472 World block Hemi. Ed heads, intake, and carbs. I hadn't noticed before, but the temp gauge starts just above the "C" when I first start, and gradually goes to about 85-90% towards the "H" and then sits there, no further change no matter how far I drive (up to about 50 miles at a gime so far). No leaking coolant. Seemingly no issues. No steam from anywhere. 1 - how to tell if the gauge is calibrated? 2 - Can it get "too hot" and cauge damage without no observable signs?
Install another mechanical gauge or use a infrared pyrometer to sample various areas.
 
or use a infrared pyrometer to sample various areas.

I bought a HAZET 1991-1 and measure at the thermostat housing mainly. Also at the coolant hose near it or the radiator. It seems to give very accurate readings.
 
66 Tribute Coronet with 472 World block Hemi. Ed heads, intake, and carbs. I hadn't noticed before, but the temp gauge starts just above the "C" when I first start, and gradually goes to about 85-90% towards the "H" and then sits there, no further change no matter how far I drive (up to about 50 miles at a gime so far). No leaking coolant. Seemingly no issues. No steam from anywhere. 1 - how to tell if the gauge is calibrated? 2 - Can it get "too hot" and cauge damage without no observable signs?
Re-reading your post it almost sounds like your gauge is not right. To me most when cold and you turn the key on will be at or below the cold mark. So is your gauge reading above the c mark when cold and the engine has sat over night?
 
Start with testing your gauge.
c-3826-jpg.jpg

If the gauge is good, normal overheating elimination process.
 
I find it hard to believe that anyone with a hemi wouldn't want mechanical gauges so you know exactly how everything is running. I have a 472 Hemi with mechanical gauges and never look at the factory gauges.
 
Well tonysrt it's a pretty accurate tribute, I don't want gauges screwed in under the dash.

Thanks to the other responders, I will try these things.
 
A tribute is fine but when a $15,000 engine overheats it could take you to the cleaners.
 
A great alternative to screwing gauges into the lower dash is to buy some really strong Neodymium magnets and mount the gauges to the magnets. They can then be stuck to the dash with no additional holes necessary. I use this concept for my tachometer.

Tach_Mount.jpg
 
So, things tried so far:
- flush/fill radiator (no air bubble present)
- New 180 degree thermostat
- new fan clutch/spring (was weak, fan not engaging until much hotter than desired)

Pyrometer aimed at the water pump housing both before and after the above still shows ~220-225C, and the gauge starts at C and goes about 80% towards the H after about 10 miles of mostly highway driving. I am hesitant to go any further from home.

I am smelling may be a problematic water pump? Flow seemed fine when I changed the coolant, and there is no noise or vibration.

I am getting pretty stumped here.
 
What’s your timing mapped out like - initial, total, vacuum advance? But sounds like gage could be off. I know on my old Corvette we basically put the sender in a pan of boiling water, pull the needle off and reset it to around 210F and make sure it returns to below the cold mark when cooled off. Don’t know if that’s possible with Chrysler gages too?
 
I bought a temp gun to get accurate temp readings for high temp gage readings in my car. you can check temp reading at thermostat and also upper and lower hose input and outputs. It's the only way to know if the gage is reading correctly. Is your system sized for the hemi? Radiator, cooling fan, fan shroud, proper mix of antifreeze 50/50? If it's a fresh engine tolerances while new cause warmer temps until a few miles during brake in. Also if it's an auto trans trans coolant lines to rad could raise temps if you have higher stall convertor. Did you put new water pump on engine? High flow pump? Fluid needs to be in radiator long enough to remove heat. That's why a temp gun is handy reading input and output from radiator will tell you improvements are working based on temp drop from input to output of radiator.
 
So, things tried so far:
- flush/fill radiator (no air bubble present)
- New 180 degree thermostat
- new fan clutch/spring (was weak, fan not engaging until much hotter than desired)

Pyrometer aimed at the water pump housing both before and after the above still shows ~220-225C, and the gauge starts at C and goes about 80% towards the H after about 10 miles of mostly highway driving. I am hesitant to go any further from home.

I am smelling may be a problematic water pump? Flow seemed fine when I changed the coolant, and there is no noise or vibration.

I am getting pretty stumped here.

220-225F

What water pump housing? I read that some of the aftermarket aluminum ones were rather restrictive.
 
You could temporarily run a mechanical gauge mounted at base of windshield on vent grill. It would allow you to eyeball calibrate temp gauge. Another idea make hinged mount you can fold back under dash with temp and oil pressure gauge. One more buy an oil pressure sender that will light the dash light if oil pressure is below 15 psi.. As said Hemis aren't cheap to repair.
 
What/who made you think that an aftermarket blocked Hemi is running too hot ? Depends on more than coolant. Whobuilt the engine ? How thigt was it built ? Friction is a major cause of "excessive" heat. Many people think engines should run at 190 ° Not even true on a low compression all iron motor. Modern fuels, higher than 9:1 CR , proper pressurized system @ 16 psi. 50/50 coolant to distilled water Thermostatic fan( should engage immediately) after 45 mph fan is really non functional.
  • At 16 psi the boiling point of a 50/50 mix is 267 degrees F. One of the easiest ways to differentiate between an expansion tank and a recovery tank is whether the tank is part of the pressurized part of the coolant system or not. Expansion Tank Set Up: An expansion tank is part of the pressurized section of the coolant system. "
 
Also remember2/3 of blades of clutch fan must be in the shrould, outer diameter of fan blades must be within 1/4 inch of diameter of shroud, then shroud must cover entire finned area of radiator, water pump impeller must be with in 60 thousands of an inch from inside back of pump housing measured with putty
 
On mine the 2 best things i did was put an aftermarket mech gauge in it. And went to a stewart components thermostat.
I thought i clicked on a 180 stat. But when it showed up was 165.

So,,I used it anyway. And my car runs in the 180 to 185 range all day as long as its moving. Even on 110 degree days. As ambient temps cool down, I may actually up it to the 180 , as it seems like thats where it wants to run anyway. I was out in it last nite and it stayed right at 165ish which in all honestly is to cool
In traffic on hot days the gauge will rise up to about 200. Maybe a tad over.....but then it cools right back down once moving.

180 on my mech gauge is about straight up dead center on the stock dash gauge. 200 is about 3/4
Mine is a real hemi car....but purist be damned....i prefer knowing exactly what the motor is doing.


edit,
Mine is .020 bore, 11.5to1 comp. 2800 stall auto. Stock hemi water pump. Recored factory stock radiator and shroud with an 18" fixed blade fan with all factory pulley arrangement. I run straight distilled water ( Im in southern AZ ) with a rislone water wetter type additive. No anti freeze of any kind.
Out here,,, When its hot out, its hot. But I dont have to worry about block freeze ups . My garage isnt heated . And " IF " it happens to get into the 30s at night. I lay a spot lamp under the car and have no worries
 
Last edited:
Auto Transport Service
Back
Top