Humvee 6.5L engine block coolant plug

Spagman

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Hello forum members,
I started servicing the cooling system on a M1025A2 equipped with a NA 6.5L that was purchased this summer and ran into an issue with coolant slowly leaking from a small hole in the driver side rear of the engine block just above the oil filter lines. This hole is between the rearmost threaded coolant plug and the transmission bell housing. When I compare the engine in the 1025A2 to the one in my 1045A2 I notice that the 1045A2 has a small plug installed in this same hole that looks like a miniature press fit freeze plug. The 1025A2 engine has what appears to be a short piece of pipe pressed into the same hole, but it is open straight through into the block. I searched the web to see if the plug for this hole is part of a standard 6.5L freeze plug set, but had no luck. Attached is a picture that I took of the 1025A2 engine with the end of a small screwdriver pointing to the hole with the protruding pipe end sticking out.

Appreciate any help you can provide on why the 1025 set up is different and where I can get the proper plug to seal this hole. Thank you.

20191027_160324_Burst01.jpg
 

Spagman

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Thanks NDT, DREDnot, and Action for your feedback. After doing some research using the information you provided I was able to find some pictures of the engine without the transmission installed that shows the drain pipe.

Now I see that my 1025A2 is actually set up with the correct valley drainage, but the 1045A2 is not. I assume that all if the 6.5L blocks have the upper valley drain hole, but without the drain pipe all the water must go into the bottom of the transmission bell housing, which can not be good. I suppose if things stay clean it will come out of the small weep hole in the bottom of the torque converter inspection cover, but this hole is small and likely clogs easily. Why they did not install the drain pipe on all of the engines by default is a bit puzzling to me.

I realize the primary reason that this drain exists in the first place is to drain diesel fuel from the engine valley should the injector pump or lines develop leaks, but on military humvees water leaks right past the hood to cowl seal (which is totally absent in the center of the hood) and accumulates in the valley.

All of this has me wondering how this issue is dealt with on the Civilian H1 variant of the truck. Surely this same water pooling issue in the intake valley does not exist on non military H1s.

Thanks again for all of the feedback.
 

NDT

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If your 1025A2 engine is a GEP, maybe that drain is something that AM General fixed that GM did not have set up very well on the GM blocks pre-2000.
 

diesel dave

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I’ve got a GEP engine and International/AM General didn’t fix anything. The drain still plugs and will ruin the injection pump if water is not drained and left in the valley for a period of time. Don’t ask me how I know.
 

Retiredwarhorses

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The trucks coming out of auction all have the drain tube removed during rebuild...thus no drain.
this is only on the rebuilt motors..which is about 99% of them. My trucks with original motors are intact. They install a plug in the hole so no water drains to the top of the torque converter...
 

Spiller

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Cos Cob, CT
The trucks coming out of auction all have the drain tube removed during rebuild...thus no drain.
this is only on the rebuilt motors..which is about 99% of them. My trucks with original motors are intact. They install a plug in the hole so no water drains to the top of the torque converter...
Hi, on my humvee (fresh from auction) the engine valley fills with water everytime it rains and is already very corroded/rusty. What is the fix for this issue? many thanks
 

Ajax MD

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LOL many thanks! guess a cover is my future as for sure won't fit in the garage :)
I've seen people fashion a rubber trim strip on the inside lip of the hood that channels rain water to the sides of the vehicle where it drains off, harmlessly. There actually is a factory piece of rubber but it's inadequate and is often rotted off and missing altogether on surplus trucks.
 

Spiller

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I've seen people fashion a rubber trim strip on the inside lip of the hood that channels rain water to the sides of the vehicle where it drains off, harmlessly. There actually is a factory piece of rubber but it's inadequate and is often rotted off and missing altogether on surplus trucks.
thanks for the idea. Fashioned one today out of a door sweep, to cover the middle exposed section. Before and after shots below. Will let you know how it works out after the next rainstorm! (Also pained the Centre strip black as was rusty and needed sanding) thanks for the tip.
6F66A79B-DE61-437A-99EB-D54FE06BE02A.jpeg94732494-9D10-42DB-8715-2058293A5BCB.jpeg
 

Ajax MD

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@Andyrv6av8r Looks good. I need to do this as well. How effective is yours?
The garage in the background leads me to think that you park indoors most of the time. Any prolonged rainfalls?
 

Andyrv6av8r

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@Andyrv6av8r Looks good. I need to do this as well. How effective is yours?
The garage in the background leads me to think that you park indoors most of the time. Any prolonged rainfalls?
Actually it's parked outside always and I had the hood up yesterday ; dry as a bone. It works well.
 

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