M38A1 Overheats!

[Tarfu43]

My A1 overheats (goes past 200 degrees) and boils-over within 10 minutes of idling. I've changed the thermostat - no help. I haven't checked the timing or carb adjustment, but the jeep starts and runs great, so I don't know how it could be a timing or carb issue. Looking in the radiator fill neck, there seems to be a lot of crud in there, so I suspect the radiator is clogged. Does that sound right to you guys? Is there a way to confirm the radiator is clogged before I start taking things apart? The TM states to clean the cooling system per TM 9-2858. What's involved with that? Should I just take the radiator to a shop and have them look at it? The first time the radiator overheated, I wasn't paying attention and the oil pressure dropped to 10 psi. Should I change the oil as a precaution?
Any help with this matter would be greatly appreciated. I'm at a standstill until I can figure this out. Thanks!

 

[AaronHorrocks]

The first thing you should do is flush your radiator!
It's easy and it's cheap. There's a joke in there somewhere...

 

[TedG]

Well my M38A1 runs 160-180. If it was mine I would drain coolant, check t'stat for correct install, disconnect the radiator hoses and reverse flush the radiator to see what crud comes out. If it is cruddy, then take it to a shop to have cleaned or recored. Prior to installing clean rad, flush the engine (drain the block and flush with water), and if real cruddy, I would consider replacing the water pump for peace of mind. This is all cheap compare to a rebuilt engine. Good luck from a former Minnie-sotan from the da cities area!

 

[armytruck63]

There could be one more sinister cause - a cracked block. This happened to my dad and me. Check for exhaust bubbles visible in the radiator with the engine running. Our block was cracked by the front-right head-stud. A freind of our with a machine shop welded up the crack for us. The M38A1 runs great now.

 

[Blood_of_Tyrants]

The next suspect is a bad water pump. With the thermostat out and the engine running, you should be able to see the coolant circulating. That is if the neck is on top of the radiator and you can look down in the radiator.

 

[WillWagner]

When it is hot, feel the lower radiator hose near the radiator. If it is cool enough to put your hand on it and leave it there, it is most likely a plugged radiator. When water pumps fail, you get fluid out the weep hole most of the time or a fan that wobbles around.

 

[stampy]

Best way I have found to clean a STEEL radiator is muratic acid. It will remove lots of crud quick just never use it on Aluminum or plastic. I use 100% flush for 5-10 min then drain, flush with water, flush again with water. Then put in new coolant. Aways wear cloves and eye protection. Muratic acid is sold at pool supply houses and Hardware stores.

 

[Tarfu43]

All,
I had the radiator overhauled. It was filled with gunk and had a small leak. The radiator came out great. I installed it this past weekend and now the jeep runs at 160-180 degrees. I also back-flushed the engine block before reinstalling the radiator.
Thanks for all the great advice!

 

[Edward Anderson]

My 1954 M38A1 is not a daily driver, but it starts and runs fine on the carport. I have a mechanical gauge that shows 150-160 degrees at idle after warm up (160 degree thermostat). Oil pressure runs about 25-30, again on a mechanical gauge. I replaced the water pump two months ago as the old one was leaking out the weep hole. It has recently developed a habit of suddenly overheating at 45-50 mph. When that happens, the engine suddenly starts to bog down and even misfire. I pull off the road and the temp goes back to 150-160. I then drive to my destination with the engine behaving normally. This has happened the last few times I have taken it out. I changed thermostats, but the problem persists. Any ideas??