Hello. This is my first post so please bare with me. First of all my dodge is a 1975 d100. She is two wheel drive regular cab. Has a 318 2 barrel carb on it and a 727 auto transmission. Getting up there in miles 96000 or so. As far as i know the engine is stock with the exception of a dual exhaust. When i got it the temp gauge did not work. I finally got it working and it was reading hot. So i removed the thermostat. Ran right in the middle to low normal range on the gauge. So i installed a new thermostat and gasket. Now it runs hot again.
When i installed the thermostat i turned the heater up high and drove/idled for 30 mins checking and adding coolant. If it does have an air lock why did it run hot with the old thermostat. Just a side note both thermostats are 192 f. I boiled the old one and it opened and closed ok. Rad looks good and no leaks or noises from the water pump. Any suggestions would be greatly appreciated
thanks


Opps forgot. It does have a fan shroud. Also has the fixed 4 blade fan.

 

1st -

Barring radiator/airflow/water pump problems:

Try a 160*, do NOT use a Mr. Gasket thermostat, just get a std Stant.
You might try a water-wetter, usually good for about 10*

Welcome to the forum.

Archer

 

Yep... worked at a parts house for years. stant is the way to go. i always told customers to remember the KISS rule haha. simple, affordable, effective.

 

Thanks for the reply. I will order a 160 today. I wonder why it had a 192 in it. It has been there a while

 

1st -

180-190 was pretty standard back in the day, but with the "new and improved" gas and old crud buildup, a lot of older engines like a little move flow.

Archer

 

Take the radiator out and back flush it with a hose... Also back flush the block the best you can while you have it apart... Sounds like you my have a restriction like Archer Suggested in his first post to you... If it has a fan Clutch test that and make sure it is working properly, and a fan shroud is a must...
Myself would say use a 180* thermostat. Lower temp stats don't regulate as well and also cause engine oil Sludging over time....

 

I move this thread to general discussion.

 

Ok. I installed a new 192 thermostat. No change. I bought radiator flush and followed the instructions. No change. I removed rad and back flushed. Lots of flow and clean water coming out. Removed one heater hose and flushed same result. Good flow. Flushed back through bottom rad hose and then through block. Seems good, no restrictions. So does that mean the pump is bad?? Its quiet and does not leak. Bearings seem tight. Or could the gauge be out of wack. I replaced the original with a used one. I ground tested it and it went to hot. It is gradual in reaching high temp after a cold start. I installed a new sending unit. Just wondering if i should put a water pump in while its apart.

 

Maaaaaaaaaan, that has to be super frustrating. Do you know anyone with access to an infrared thermometer? Shops use them, maybe they’d let ya point theirs at the engine for a couple bucks. Other than that, yeah, only thing I can think is maybe the impellers in the water pump are bad but the bearings are holding. Heat issues drive me nuts, always have.

 

1st -

The IR thermometer is a good idea, and they are pretty cheap - try Harbor Freight.

Yes, the pump could be bad, but ... if the pump was working, you should see water moving through the radiator cap hole (don't do this hot).
You said that removing the t-stat helped, but going to a 192 didn't. That doesn't make sense.

As far as the gauge, you can pick up a cheap mechanical one and plug it into a water jacket fitting for a test.

Archer

 

i always ran 180s in my rides. i added an elec fan to my Plymouth and it ran ice cold lmao.

 

Thanks for all the advice. I finally had time to put everything back together after i flushed the system. Same water pump(after i removed and inspected),the new 192 thermostat, and original 4 blade fixed fan and shroud. To my surprise it seems to in the low range of normal on the gauge. I guess i had a blockage or an air pocket. Im going to get the compression and timing checked so at the same time i will get them to check the engine temp with a temp gun for peace of mind.
thanks again

 

Wait a minute...... 4 Blade fan????? I think those are for Slant Sixes?????? That truck should have a 5 or 6 Blade Fan as far as I recall.... ????????

 

ahhhhhhhhhh! nice catch!

 

Interesting. I take parts off a 1972 with a 7 blade fixed fan. The other truck at the junkyard is a 1975 d100 with 318 and it has the 4 blade fixed same as mine

 

ya know, thinking back, i can't remember how many there were on my stock 318... i coulda sworn five but that was some time ago haha.

 

I'll take your work for it.... I'm getting old you know.... LOL