Radiator Repair Suggestions

mtdave · Post by **mtdave** » Fri Jul 08, 2011 9:30 am

Well I'm still fighting an overheating issue on my 1950 M38. I replaced the water pump which was leaking badly, put in a new thermostat with the correct spacer and a new radiator cap and then she started this overheating thing. I tested the thermostat, it's ok. My mechanic that works on my "modern" vehicles lent me several hi-tech devices to run some further tests in case I have a head gasket issue. These include a gizmo to test for combustion gases in the radiator, coolant in the exhaust gases and a tool that would remove an air pocket in the cooling system. All tests came back negative. The one thing I notice is that the water pump has a distinctive rattle when it gets really hot. Could I have a pump issue like the impeller working loose from the shaft when it gets that hot. My parts supplier says "no way" and I don't doubt his word but stranger things have happened. I'm leaning towards a plugged radiator now since it's now leaking in a dozen different places, possibly caused by all this overheating and or the new pump and cap putting more pressure on the system. I checked the local raditor shop and he said a unit that old would probably need a recore at about $500.00. I'm open to suggestions from the panel of experts before I spend that much money.

Post by **wesk** » Fri Jul 08, 2011 10:00 am

Take the radiator out of the jeep and drop it at the radiator shop for an inspection. They will tell you very quickly if it can be rodded clean and patched or if it needs to be re-cored. If not comfortable with their answer get a second shop's opinion.

A plugged radiator is usually simple to diagnose on the jeep if you have the experience and just observe coolant flow rate through the upper tank. When you open the block drain petcock do you get an immediate flow of clean coolant. If no flow or rusty low flow then you will need to get the block flushed as well.

A pump can rattle when it is pushing coolant against a block radiator or engine block.

RICKG · Post by **RICKG** » Fri Jul 08, 2011 10:03 am

I wont pretend to know the cause of the overheating but i will
say that chasing leaks in old radiators is futile. It seemed
for every leak i killed, 5 would show up for the funeral..
I went the recore route and bit the bullet for about $450.
I havent fired it up yet but im confident that i'll have a
well functioning cooling system.

Bretto · Post by **Bretto** » Fri Jul 08, 2011 10:32 am

RICKG wrote:It seemed
for every leak i killed, 5 would show up for the funeral..

that was humorous

bubagun · Post by **bubagun** » Fri Jul 08, 2011 11:15 am

I have rebuilt a few Jeep engines, both flatheads and OHV's. Many times the blocks have had their water passages pretty much plugged up with that "stop Leak" crap. Itl lays inside the blocks coolant passages like thick stiff mud. They will overheat if coolant cannot circulate arount the cylinders...and to and from.. the water pump/radiator.

Post by **wesk** » Fri Jul 08, 2011 12:20 pm

Often using a power back flush system will clean the block out well enough.

Make sure you have the correct pressure cap. Max pressure is listed in the operator's TM's.

mtdave · Post by **mtdave** » Fri Jul 08, 2011 12:41 pm

Wes I hate to admit it but I've never noticed a block petcock

where is it located? With all my crawling around I've not seen one and don't see one in the parts illustrations. But even with checking that she cooled just fine until the water pump went out and the radiator started leaking. I'll check it out this weekend time and weather permitting. My work area is under the big sky we call Montana so I have to dodge thunderstorms, hail and the sun.

RICKG · Post by **RICKG** » Fri Jul 08, 2011 1:42 pm

the block water drain petcock is on the rt side of the block
between the starter and gen.

BullRun · Post by **BullRun** » Fri Jul 08, 2011 5:07 pm

This is a long shot but worth considering now that it has been decades since these jeeps were new.

A friend of mine was an Army and then National Guard jeep mechanic for 35 years and then more in retirement. He always told me that if you take an L-Head or F-Head and bore the engine to .060 and greater the engines tend to overheat as the cylinder walls get too thin so it is better to sleeve them in a rebuild.

I remember seeing .060, .080 and even greater cylinder/engine rebuild kits from J.C. Whitney in the past... maybe your engine is way overbored?

Oldsalt · Post by **Oldsalt** » Fri Jul 08, 2011 5:29 pm

Any chance the thermostat is upside down?

oilleaker1 · Post by **oilleaker1** » Fri Jul 08, 2011 7:22 pm

Go to G503 MB/GPW Tech. and open thread GPW running hot. 8 pages of this problem discussed!!!!!!!!!!!!!

John

Post by **wesk** » Fri Jul 08, 2011 8:40 pm

It's simply amazing folks can fill 8 pages with the basic checks needed to sort out an overheating l134.

1 - Is the temp gauge correct!

2 - Is there clean coolant in the system?

3 - Does it circulate when the engine is running? Are there any air bubbles while it is circulating?

4 - If it circulates with the engine running is the ignition timing correct.

5 - If it circulates with the engine running is the thermostat opening and closing at correct temps?

6 - If it circulates with the engine running but you get a lot of air bubbles then do a compression check and look for the source of the air bubbles.

7 - If it does not circulate with the engine running check thermostat for operation and opening temps.

8 - If the thermostat checks ok reverse flush the radiator and block.

9 - If still no circulation inspect the fuel water pump.

10 - Check pressure cap for proper operation and correct pressure relief value.

If a large overbore is the culprit you would have had a hot running issue all along.

Some really handy tools to have on the shelf for this exercise are: mechanical thermometer, digital temp gun, coolant system pressure testing kit, a known good mechanical temp gauge and a power flushing kit.

Verification of gauge function is very easy to do. Just immerse the sender in a pan of water supporting it so it doesn't touch the metal sides or bottom and insert a mechanical thermometer in the water the same way. Heat it on one of those portable electric burner units and compare the temp gauge reading to the thermometer reading all the way til she boils at 212 degrees or so.

artificer · Post by **artificer** » Sat Jul 09, 2011 2:24 pm

then she started this overheating thing

BTW what do you call overheating?
What did you do exactly to cause this? Look there first.
It was not overheating before?
Kind of rules out the radiator, unless you disturbed a lot of crud & this should be evident if you pressure clean radiator bottom to top.

What seems funny to me [let alone the 8 pages of repetitive stuff] is that no-one thinks past the issue of "the coolant system being the only cause of overheating" & they go round & round in circles.
What about ignition timing being retarded or the mechanical/vacuum advance not working for one or what about running too lean or dragging brakes....think outside of the box.
Hook up a vacuum gauge & check a few things with it.
The over boring thing is just a red herring.

mtdave · Post by **mtdave** » Mon Jul 11, 2011 8:36 am

RICKG wrote:the block water drain petcock is on the rt side of the block
between the starter and gen.

Now I know why I never saw a petcock in the block, it doesn't have one. Mine has a hex head plug someone over the years stuck in there. When I pulled the plug she flowed nice clean green antifreeze. And to answer all the other questions:
1) I consider overheating when the needle pegs the gauge and antifreeze comes blowing out the radiator cap and all the pin holes in the radiator.
2) Thermostat is in correct I double double checked and even tried the old thermostat and bought the correct spacer since mine had some odd straight sided sleeve in there not the proper tapered spacer.
3) As stated originally I used all the high tech tools to detect gases and antifreeze where they shouldn't be.
4) And in a nut shell everything was fine untill the water pump went tits up. Changing the thermostat and radiator cap were just SOP when doing a water pump. I pointed my problem at the new water pump since it's the major component I replaced and only started thinking clogged radiator because it started leaking after the pump was replaced. I'm not dismissing anybodys ideas but I think I've covered most of the bases.

Post by **wesk** » Mon Jul 11, 2011 9:03 am

Did you test the new thermostat? That is an absolute must everytime you change one. You put it in a pan of water along with a thermometer and heat the water and observe that the thermostat starts to open at the correct temp, reaches full open, and starts to close at the crrect temp and is fully closed when done. I have encountered bad thermostats new in the box often.

The leaky radiator after installing a new pump and pressure cap means the old radiator was tired and will need work. If of course the new pressure cap is the correct pressure? The M38/M38A1/M170 are 4 1/2 Lbs. Most modern replacement caps in the stores are 7 to 15 Lbs.