Posted: Tue Jul 04, 2017 9:40 pm Post subject: M38A1 Missing Oil Pressure in Places
Hey! I have an oil pressure problem on my M38A1. The engine arrived with multiple bubbaized oil lines including a 1/4" jumper line between the two rear holes on the oil gallery group on the driver's side of the block. After re-plumbing all external oil lines and installing the missing timing gear spray fitting, I have minimal oil flow to the filter housing and none, "0" to the line on the top rear of the cylinder head. That means that there is no lubrication to the rocker arm assembly.
The oil pan and pickup were solvent flushed spotless after removal from the block.
The camshaft seems to have excessive play front to rear. WTH? What controls that on this motor? The thrust washer is there. Is there also a plug or spring at the rear of the camshaft?
The bottom line question is: "Should I just replace the oil pump or is there a procedure to check/flush the oil gallery that I should try first?"
This is not my first time at the rodeo, but, these little powerplants are a far cry from big diesels I am used to. Somebody send me a life preserver please.
I moved your post to the tech board. This board is for members to show the ongoing status of their resto project as it progresses.
The previous installation of a jumper tube to help with top oil is a clue that the gallery has been plugging up. Start by hooking up a direct reading oil pressure gage to the 1/8" pipe plugs along the gallery one at a time and record the pressure readings you get. If you do get variable readings then odds are there's a lot of trash in the gallery. The only good and safe way to clean the galleries out is by hot tanking the block. Wire picking and flushing fluids or air pressure will only move the trash somewhere else. The smaller feeds to the cam and the crank main/rod bearings may already be plugged or your attempts at pressure cleaning my just move the trash to new places.
The cam has a welsh plug at it's rear bore. Excessive forward/aft movement means worn bearing thrust plate and or retainer.
Just a quick update to the oil gallery problem. We removed the front fitting (oil filter feed) and the two rear fittings ( Oil pressure sender and cylinder head oil feed). Using a 1/4" neoprene fuel line attached to a 1'8" MPT X 1/4" Hose barb adapter, we gently blew through the gallery by mouth. Air escaped from the lower of the two rear holes but not the upper. Clogged by what appears to be carbonized oil residue.
No attempt was made to flush out the gallery or to jeopardize any of the bearings by pressurized air.
An alternative was considered to use a 24 volt fuel pump to suck out the gallery with the front hole providing a supply of ATF as a solvent. This would minimize the possibility of contaminating the bearings by providing vacuum at them instead of pressure. Since it was the upper hole that was clogged, no attempt was made to use this method.
In the end, the lower hole was fitted with a 45 deg, 1/8"MPT X 1/4" FPT street elbow, 1/4" chase nipple, 1/8" X 1/4" X 1/8" FPT Tee and two 1/8" MTP X 1/4" Hose barb fittings and the connections made by 1/4" neoprene hose. Since there is no flow to the oil sender, (just a static pressure line) oil flow to the rockers remains undiminished despite sharing the same output hole in the gallery.
At this point, we still don't know what the condition of the cam and crank bearings are, but, at least we know that there is oil flow at all the visible places and that the engine runs fairly quietly as is.
You are certainly optimistic the engine will survive unscathed at least in the near future. Hope you get lucky but seeing oil at 3 of the external main oil gallery pipe plugs is no guarantee all passageways to all the critical internal passageways are unplugged or un-restricted. Any remaining restriction can still destroy or shorten the life of the Rod/main bearings, Front cam bearing and and the back 3 block cam bores as well as each lifter bore. We'll all say a prayer for you! _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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