MGB Oil Filter Problem 77 MGB

[kyreb1862]

Had a strange experience with an oil filter yesterday. I changed oil on my "B" and replaced the Fram oil filter on the car with a new Bosch oil filter from my local Auto Zone. I started the car up and noticed that the oil pressure was only reading about 20 pounds. I immediately shut the car off and checked the fluid levels and looked for leaks, everything was good. I started the car again, same problem. This time I removed the Bosch filter and retrieved the Fram I had just taken off. The Fram on cold start had always given 70+ pounds of oil pressure. I put the Fram back on the car and started up, I was immediately rewarded with 70+ pounds of oil pressure. Has anyone else ever had this happen? It was a new one on me. I'm taking the filter back to Auto Zone on Monday and discussing it with them.

 

[Steve_S]

My only suggestion is to buy a quality filter. Napa Gold and K&N are both highly regarded.

 

[kyreb1862]

My only suggestion is to buy a quality filter. Napa Gold and K&N are both highly regarded.

According to the info I came up with Bosch was supposed to be a high quality filter. Maybe I just got a bad one !

 

[Steve_S]

Maybe. I've never used one so I can't say for sure.

 

[DJThom]

When you took the filter off, was it filled with oil or dry?

perhaps it's the oil bypass on the filter housing. It only allows a 2 psi pressure drop accross the filter before flipping into bypass mode. The theory is dirty oil is better than no oil.

As the oil warms up and drops in viscosity, the pressure drop dips below the threashold and oil starts going through the filter again.

you could try filling the filter with oil to wet the paper and "prime the pump" as it were.

 

[Camshaft]

What's the part # for the "proper" K&N filter?

 

[Steve_S]

I'm not sure if a '74.5 filter is inverted or hanging, or if it would be the same as my earlier car, but on my RHD '67 which uses an inverted filter, I use K&N HP-2004. On a couple other cars with the Moss hanging spin-on adapter I use HP-2007.

Cross reference charts:
https://www.knfilters.com/search/kn_cross_ref.aspx?kn=HP-2004
https://www.knfilters.com/search/kn_cross_ref.aspx?kn=HP-2007

 

[Camshaft]

Mine takes a spin-on filter, and it's inverted.

 

[Steve_S]

I believe the 2004 is your filter but I'd suggest confirming with a mate model owner. Or order a Wix brand from Moss which are also highly regarded.

 

[Camshaft]

Thanks for your help Steve! Will do.

 

[MgKid1974]

you might want to just crank the engine with no spark to see if you have oil pressure when you put on the new filter...not too sure if it will make a difference on engine wear compared to firing it up...just a habit I get into whenever I have pressure problems.