Radiator Repair Suggestions

mtdave · Posted: Fri Jul 08, 2011 9:30 am Post subject: Radiator Repair Suggestions

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.
_________________
Huntin'-Trappin-Fishin'-Jeep fixin' that's all I do.
Ball sports are boring.
Stock car racing is ok.

wesk · Posted: Fri Jul 08, 2011 10:00 am Post subject:

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.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

RICKG · Member Joined: Aug 31, 2010 Posts: 1741 Location: SO IDAHO

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.
_________________
keep 'em rollin'
RICKG MC 51986 DOD 01-52, '50 CJ3a

Bretto · Member Joined: Nov 24, 2010 Posts: 1390 Location: Orem, UT

bubagun · Member Joined: Jan 11, 2007 Posts: 66

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.
_________________
1950-M38, 1952-M38, 1964 M151A1, Mechanical Mule, 1945 CCKW,M100 trailer, M416 trailer.

wesk · Posted: Fri Jul 08, 2011 12:20 pm Post subject:

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.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

mtdave · Posted: Fri Jul 08, 2011 12:41 pm Post subject:

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

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.
_________________
Huntin'-Trappin-Fishin'-Jeep fixin' that's all I do.
Ball sports are boring.
Stock car racing is ok.

RICKG · Member Joined: Aug 31, 2010 Posts: 1741 Location: SO IDAHO

the block water drain petcock is on the rt side of the block
between the starter and gen.
_________________
keep 'em rollin'
RICKG MC 51986 DOD 01-52, '50 CJ3a

BullRun · Member Joined: Mar 10, 2009 Posts: 459

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 · Member Joined: Jan 28, 2010 Posts: 179 Location: Texas

Any chance the thermostat is upside down?

oilleaker1 · Posted: Fri Jul 08, 2011 7:22 pm Post subject:

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

John

wesk · Posted: Fri Jul 08, 2011 8:40 pm Post subject:

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

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.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

artificer · Posted: Sat Jul 09, 2011 2:24 pm Post subject:

mtdave · Posted: Mon Jul 11, 2011 8:36 am Post subject:

wesk · Posted: Mon Jul 11, 2011 9:03 am Post subject:

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.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php


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