1966 304 Not Getting to Temp

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Hello, again, I recently changed my thermostat to a robertshaw 180°
www.ihpartsamerica.com

Robertshaw Thermostat for IH International Harvester 152, 196, 266, 304, 345 or 392 Engine

Check out the deal on Robertshaw Thermostat for IH International Harvester 152, 196, 266, 304, 345 or 392 Engine at IH Parts America
www.ihpartsamerica.com

I also just installed my new coolant temp gauge as well (threaded nicely into the top right of the engine, I think it’s the manifold.

The engine gets up to around 150° and doesn’t seem to get hotter than that. I let it idle for about 20 minutes expecting for the thermostat to open, and I would top off the radiator, but it never happened.

From what I’ve read online, either the thermostat is bad (I think unlikely) or maybe I installed it somehow allowing coolant to bypass the thermostat. That seems unlikely too honestly. The install seemed so obvious.

Any ideas?
 
How long was the engine allowed to run? I'm highly dubious that one of these old cooling systems could be efficient enough to maintain the coolant temp at 150 for any great length of time. Is the location used for the coolant temp sender being reached by the coolant? T-stats can be checked for function in a pot of heated water on the stovetop with a cooking thermometer.
 
I allowed it to idle for more than 20 minutes. It was 40°F outside, but I’m sure that doesn’t make a big difference. OEM gauge read just under halfway. New mechanical gauge was 150° ish ( the scale and labeling kinda sucks on this gauge)

Dorman 7-123 Water Temperature Gauge https://www.amazon.com/dp/B002ET4O5...abc_1GF926FRXRJPDCCA9E2P?_encoding=UTF8&psc=1

When I installed I used RTV blue to seal the threads. Decided after I filled with coolant to use thread tape instead. So I pulled out the sensor and it gushed coolant, so I think it’s being reached.
 
It probably doesn’t make a huge difference, but I did a fair bit of work to the cooling system.

I had the radiator rebuilt with a new core because it was leaking.
I bypassed the heater (trying to save money by not replacing it, $10k ago)
I flushed the system and replaced all the soft lines
New water pump
New 180° thermostat (not sure what was in there before or if it was working correctly)
Also I don’t have a fan clutch although I want one after reading another post on this sub forum yesterday!
 
Sometimes a bit of debris can get in the thermostat. Take it out and run it down the freeway before you decide there is a problem.
 
I can’t even run it down the driveway as it is now haha

I’ll wait until I can drive it and come back. Thanks
 
Did you verify you actually ordered/received a 180 and not a 160 degree thermostat? If it was the 160 version your situation is probably within gauge error.
 
I didn’t think to test it. The coolant return line definitely got hot, maybe that means the thermostat was open?

I’ll pull it out and toss it in a pot to see where it opens.
 
When running the engine you'll know the thermostat is working on a 40 degree day when you feel heat coming from the air being blown thru the radiator. A lot of aftermarket gauges are not the most accurate. And if your new gauge is electric, make sure the threads on the sending unit are making good contact with the engine. By putting on a lot of thread sealant or teflon tape on the sending unit, you could be affecting its overall reading if it is not getting a good ground. If the gauge checks out and you decide to pop out the thermostat to verify we didn't screw up and send you the wrong temp, there will be a set of numbers on the side of it. That is the part number that we can verify the correct thermostat was sent.
 
Be careful, my wife's kitchen thermometer wasn't very accurate measuring the water temp. I ended up using my IR thermometer
 
My new gauge is mechanical, it has leads for a light, but I haven’t hooked them up yet. I used thread tape, so if it needs to be grounded, it’s likely not touching at all. I tested all this by running straight out of a gas can. Seems like a pretty bad idea. I just ordered a new tank from Binder Boneyard, so I’ll just wait 10-12 weeks and come back to this. Thanks!


@meisterj thanks for the tip! Sounds like part number is the way to go without an IR thermometer... not that I didn’t need another reason to want one haha
 
That sender doesn't need a ground in your case. The gauge face scale is a bit gappy, especially in the most critical 150 to 210 range, which is where you'd like to have the most detail and tick marks for best monitoring of these engines. With a properly working stock Temp or Oil gauge, anywhere on the horizontal line is supposed to indicate normal, with dead center of the line being ideal temp or oil pressure. That still doesn't totally bless your stock gauge yet, but it is encouraging to see that it reads about half way. IR thermo's from places like horror fright tulz are inexpensive and make great diagnostic tools. It can be very helpful and informative to be able to take instant readings at various points of the coolant passageways.
 
Where did you get the new thermostat? Robert Shaw stopped that retail production a number of years ago. 99% of the "New" Robert Shaw styled stated are Chinese crap. they can leak coolant through the center seal and make it hard to reach temperature. I had 2 in a row do this, just put the old true RS back in and fixed the issue. 40 degrees is cold enough for a small leak past the stat to significantly delay reaching opening temp.
 
Robert Kenney said:
Where did you get the new thermostat? Robert Shaw stopped that retail production a number of years ago. 99% of the "New" Robert Shaw styled stated are Chinese crap. they can leak coolant through the center seal and make it hard to reach temperature. I had 2 in a row do this, just put the old true RS back in and fixed the issue. 40 degrees is cold enough for a small leak past the stat to significantly delay reaching opening temp.
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Robert, I believe he bought the thermostat thru IHPA. We are still able to purchase USA made Robertshaw thermostats that are still made here in the USA. We buy them in cases of 105 units per case and then repackage them.
 
That’s correct, I got mine from IHPA, so I trust it’s a quality unit.

One thing I’m uncertain about is the thermostat gaskets. On IHPA, it mentions two gaskets are usually needed. Why is this the case? Should it be RTV>gasket>RTV>gasket>RTV? I’m not noticing any leaking at the housing, but it also hasn’t really gotten up to temp so it’s hard to know. This probably wouldn’t cause slow heating though.
 
The two gaskets are because the t-stat housing is removable along with the upper water neck fitting that caps the t-stat. So from the bottom, it's gasket 1 - housing - t-stat - gasket 2 - upper neck. I'm not big on the RTV. If used at all here, it should be a very thin and even smear only. I prefer a product called Copper Coat. Gasgacinch is also good. These will not spoog up and break off into little snot boogers when compressed the way excess RTV is known to do.
 
That's great info, thanks! I didn't remove the t-stat housing, so I'm hoping there won't be any leaks. Hopefully things are okay with this RTV.
 
If you laid a bead of RTV and then compressed things together, then you have excess RTV pooping out with the potential to slough off and get to places where it doesn't belong. If you finger smeared it thinly and evenly prior to assembly, then it will be fine.
 
I did finger smear a thin layer, but I can see some RTV pushing out of the housing. I wouldn't be surprised if some was pushing on the inside as well. I did buy that second gasket just in case, so I can redo it. This wouldn't be the cause of the trouble getting to temp would it?
 
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