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MG MGA - recurring low oil pressure

The quick motor history on my is that I had a 1500 engine that was in an MGA when I purchased it in 1976 that similarly did not have the machining for the tach drive output. The engine number is 15K 926. I have been curious about the number for a long time...great engine that ran without any problems for 35 years in my car. Any ideas what the origin of this motor would be? It replaced the original motor which was number BP 15GB 23596. I subsequently found an original MGA 1500 replacement motor around 1994 that I finally put into my car in 2013. The replacement engine has number BP15GB-19276.

I am not sure how long it took to produce the 4000 units in between...but I am having issues with low oil pressure and overheating in the rebuilt motor. I was wondering if there were any inherent problems associated with this era of motors that may have caused my original motor to be removed and also endemic to my replacement? I have had to rebuild the rebuilt motor a second time under warranty repair by the same mechanic after very low pressure and found the #3 and #4 main bearings to be burned up. Since the repair went back in this past January I have been having overheating problems and again, low oil pressure is reappearing. It's as low as 25-30 psi running at 2500-3000 RPM.

Any thoughts how to solve it now?

Steve Lofaro

Stephen Lofaro

Read Barney's page on oil path flow
And see John Twist's video on causes of low oil pressure. Link on mgaguru page
Then work your way through the items that can be checked with the engine in place. If this doesn't solve your problem then it is an engine dismantle to check clearances ie plasti-gage
Check oil quality, relief valve and oil pump condition would be my first items to check.
Mike Ellsmore

MY 1958 MGA started having low pressure at idle, 5-10 PSI, on very hot days when idling at stops. I replaced the oil pump (which turned out to be the original first type), shimmed the pump spring, as per Twist's recommendation, and replaced the rod bearings. That was 15 years ago and the oil pressure runs strong with very little variation. I use Castrol 20-50W.
Bill Haglan

This thread was discussed on 23/10/2015

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