Over flowing radiator

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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Shug4
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Over flowing radiator

Post by Shug4 » Sun Feb 10, 2019 9:10 pm

When I first start up my m38a1 antifreeze pours out the overflow tube it also flows out the top of my radiator when I stop engine and undo the cap. This happens when antifreeze is cold. What causes this?

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Re: Over flowing radiator

Post by Ben Dover » Sun Feb 10, 2019 10:20 pm

Is it a 4# CAP Does it have a rubber seal on the valve or is it the early type that is used with the fiber seal in the filler neck?
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artificer
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Re: Over flowing radiator

Post by artificer » Mon Feb 11, 2019 1:06 am

First the coolant should not be filled right to the top but about 2 knuckles under the bottom of the filler neck.
Leave the cap off & startup if there are bubbles it is indicative of a blown head gasket.
If so, check by doing a compression test 'properly'.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Over flowing radiator

Post by Ben Dover » Mon Feb 11, 2019 8:56 am

M-38A1 is usually not that touchy with correct cap.
Does your engine still have the bypass elbow between the head and the waterpump?
Again which cap do you have?
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
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COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

Shug4
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Re: Over flowing radiator

Post by Shug4 » Fri Feb 15, 2019 6:17 pm

Will check on the bypass elbow.


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Re: Over flowing radiator

Post by Shug4 » Fri Feb 15, 2019 6:21 pm

It looks like I might have a head gasket blown because when I start it up it blows grey smoke out the exhaust. Also I have the cap with the rubber seat in it. I think it is smaller than the neck.

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Re: Over flowing radiator

Post by artificer » Fri Feb 15, 2019 6:49 pm

To work as intended radiator caps must be the correct length for the rubber or composite material to seat in the radiator neck.
Blown head gasket will show on a properly conducted compression test or bubbles will show up in the radiator on a leak down test isolating 1 or more cylinders.
Smoke can be indicative of many things & grey is not usually associated with head gasket, white is.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Over flowing radiator

Post by Ben Dover » Fri Feb 15, 2019 11:17 pm

Can you post a pic of the type radiator cap you are using? If the valve on the cap has the rubber seal, there is no ned for the fibre seal in the neck. Steam upon start up is not a good sign. Does it stop after a few seconds?
Evidence of coolant in a cylinder is indicated by a spark plug with little or no deposits when compared to the others, also, rust may be on the tip of the spark plug in the affected cylinder.
Removing the spark plugs will give you a quick answer.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

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