Engine Oil

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Engine Oil

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Engine Oil

Postby kmam » December 22nd, 2017, 6:29 am

My engine has been completely rebuilt and is in virtually new condition. I am measuring oil pressure with a professional gauge connected instead of the normal sensor. I am using 20W-50 oil. When the engine is cold I have oil pressure of just under 35psi. However when it warms up the pressure drops and after it has been turned off a few minutes then restarted the presssure is 0! The ambient temperature is around 32+C or about 86F. I have bought heavier grade oil today and will try it tomorrow.

I am wondering what grade oil the US Army used in the M151 when operating in consistently high ambient temperatures? I have the manuals and know what is specified but I wonder what was used in the real World.
Howard

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AM General M151A2
RAAF Tactical Trailer
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Re: Engine Oil

Postby rickf » December 22nd, 2017, 8:17 am

The Army called for straight 30 weight and in later years went to 15W-40, the same that they used in all of the diesels. 20-50 is pretty heavy, don't go any heavier than that. If you have no oil pressure than it is a mechanical issue and the weight of the oil will not change things. The fact that you had pressure and it went away and also the fact that this engine is new and all the clearances have been checked I would say the pressure relief valve spring in the oil pump failed. You are probably still getting oil flow but no pressure. That is not going to be good for the cam bearings and especially the top end so don't keep running it. If you want to do a quick check to verify that it still has flow take the filter off and crank it and see if oil comes out. I really hate to say this but it doesn't really matter if it does or not, you still have to get the oil pump out and see what the issue is with it. Was it a new pump or the old one?
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: Engine Oil

Postby rickf » December 22nd, 2017, 8:41 am

I am thinking that if you are using the original oil pump and that heavy oil and with the new tight clearances you could have pushed the pressure relief valve all the way back in it's bore and back into an area where there was varnish from non use from before and it may have stuck there.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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