Oil pressure



Have an MGTF 1250cc with 60,000 miles that shows constant 10# oil pressure even with increased engine speed. Ready to rebuild oil pump, but would expect “tired” pump to at least increase oil pressure with RPMs. Any other ideas?


Is the gauge stuck?


No, I replaced the gauge.


Have you inspected the oil pressure relief valve? Perhaps it is sticking open a bit.


have “examined” oil pressure relief valve appears fine but I have no way to measure spring tension and to know if ball is worn. oil line behind guage barely dripping oil when engine is reved but appears to have plenty of oil at top end when adjusting valves. thinking of removing oil line at bottom of engine (that feeds to top) and check oil flow - appears you don’t think its the pump either. first time with this problem. @ 60lbs pressure this oil should shoot out when I turn it over???


How about the sensor?


I would either check the pressure with an external gauge since this removes the car’s system from the equation or replace the oil pressure sending unit.

An old oil press. sender often develops a higher electrical resistance over time. Higher resistance always forces the needle to read lower than normal even with normal oil pressure being present.
This is also true of temp and fuel gauges.


My TF has a mechanical pressure gauge. I have just observed flow from the block to the pressure gauge line, lots of oil, but pressure??
Will test at gauge end tomorrow. Thanks for the help, any other suggestions?


The gauge could be off, but I’m voting for the pressure relief spring being weak.


You could put a ball bearing at BOTH ends of the spring and see if that increases oil pressure. Wear on the ball or its seat is not really an issue here. A little leakage would not make that much difference.

I once had a girlfriend with an old MG. One night with her driving the gauge line broke and covered her white dress with hot, black oil…The last time I saw her she was driving a Studebaker Hawk.


Caddyman makes a good point. The gauge on your TF is connected to the engine by a tube full of oil, as opposed to an electrical connection, correct? Is there an obstruction within the oil pressure tube?


Caddyman’s idea of second ball bearing got us from 10# to 20# of pressure however, what’s coming out of gauge feed end wouldn’t ruin anyone’s dress. Finger over exit from engine to gauge doesn’t give any feel of pressure. For Mcparadise we took all lines out and blue them out with air pressure used 2 sets of lines and two different gauges got to 25# on engine reving. This is first time we have seen reaction to engine speed and oil pressure. Now it sounds like oil pump problem to me. Preparing to order parts and rebuild, and cancelling plans to drive to car show. Thanks for all the help. Any contrary thoughts to proposed action I’m all ears - have to loosen steering column and raise engine to get to pump, will try anything first!!


Oil pumps do eventually fail, I just had to replace an oil pump (and drive chain) on a benz diesel engine (almost 400K miles). Similar symptoms, the pressure was reading lower than normal, especially when hot.


It could be the pump or the pressure relief spring, or it could have just developed a case of loose bearings. Hey, it’s TF with 60K miles. It’s to be expected. I’m sure you can get a pump from Moss Motors or Victoria British, but you might want to check the bearings with plastigauge just to be safe. It’s too valuable an engine to ruin.

Also consider asking your question at http://www.british-cars.co.uk/ You have to “join” but it’s free. There are forums on just about any British car you can name.