The MGA With An Attitude

  Felt oil filter element
Felt Oil
Filter Element

This picture is an absolute mess, and the engine it came from is also an absolute mess. The oil filter in the picture, or what remains of it, was originally a felt filter (picture at right). This is the type of filter you see illustrated in the Workshop Manual and the Service Parts List. It has been the old reliable filter for decades, preferred by some for the depth penetration filtering and dirt holding capability. In this case, for some entirely unknown reason, it not only failed but also ruined a nearly new engine. We can only HOPE that this is a freak incident, a single isolated case, and that it may never happen again.

Failed Felt Filter
Click for larger image

On October 14, 2011, Don Livingood in Medford, Oregon, USA wrote:
"I recently encountered a problem that I have never heard of before. I have attached a photo for reference.
I have a 1959 MGA 1500. I finished a frame up restoration on it in June of 2008. I currently have about 12,000 miles on the new engine. I drive the car regularly in good weather. I change the oil and filter at about 3000 miles or every year, whichever occurs first, usually the miles. I take good care of the car and it usually takes some sort of prize when entered in a show. I tell you all this so that you will know that this car receives better than average upkeep.
A week or so ago I was headed to California (I live in Oregon) for a show. This is about 300 miles and the first 200 is on the super slab. I don’t drive her fast, she has all the original gearing, I usually am floating along at about 60 to 65 MPH, trying to keep her under 3500 RPM. It was hot, about 95 F, and the engine temp did get up over 200 for awhile. When I stopped for a break after leaving the freeway I opened the hood and let her cool off for about 1/2 hour. Then I was into the 2 lane, lazy country roads for the rest of the trip.
Trouble is as soon as I was off the freeway (top has been down all the way) I could hear a rattle that I knew right away was rod bearing float. I shut her down and checked the oil. It was black! It was a nice clear amber when I left the house and right at the full mark. From there I had the car brought home on the back of a trailer. I dropped the pan and filter and found the mess I have attached. The filter screen was plugged almost solid.
The original filter was a Moss 950-510 in the original filter cartridge. As you can see, it kind of melted down into a black sticky sludge which almost totally plugged up the oil pump pickup screen. I have cleaned everything up and flushed the engine. A short run after reaching temp shows that the engine is probably ruined. Rod rattle is evident if the RPMs are raised a little and the oil pressure hovers around 20 or lower. I may be able to replace the rod bearings to get some more life out if the engine but if that much damage was done to them I suspect the rest of the engine is now as equally worn.
There was never any ”knocking” of the rods so the crank may still be OK. I may throw in a set of rod bearings to see if the car will be drivable but I am going to build another engine, I would never be trusting of this one now. I have been thinking of swapping in an 1800 anyway.
The big issue is: Have you ever heard of this before? I have been running Joe Gibbs oil in it because of the zinc content. Is there any reason this oil should not be compatible with the Moss filter?
Anyway one for the books for me. A pretty expensive experience"!

On follow up Don comments:
"There is no water in the oil. Head gasket is fine. Engine runs now. The sludge is the result of the filter coming apart. Check the picture, nothing left but screen. The filter material is almost all gone. There is a little left around the edges. It was the filter material that clogged the oil pickup screen.

Chuck Schaefer in West Chicago,IL, USA asked:
"Have you asked Moss to comment on their filter yet? It would appear that the felt has left the filter element and clogged your oil pump inlet. Moss supplies this filter from various manufacturers so it would help if you knew which brand filter you used so you could alert the rest of us. It may be related to just one manufacturer.
It would seem that the earlier oil pump strainer was revised. It might be good time to 'upgrade' to the 'newer' 53 year old oil pump cover and screen design?.

To which Don responded:
"I think you are right on all counts. I still have the box the filter came in so maybe we can pin down the manufacture. It is listed in the catalog as 'from various sources'. I have already changed over to the spin on adapter and installed a WIX filter. It's too late! I just dropped a rod cap and the bearing is down to copper and the shaft is scoured. I am not sure how much else damage has been done to this 1500 engine. I am going to call and talk with Moss next week and will report what I hear from them. The main reason I posted this was to alert others to the possible problem. I only stayed with the original filter to begin with to remain 'Correct' for shows".

And Barney comments:
"For the felt to get from the filter to the sump it has to go through the crankshaft bearings, and the camshaft bearings, and the rocker shaft bushings, and all of the small bore oil galleries in the engine block. I can imagine the whole engine may be thoroughly clogged with the fibers, not just in the sump. So it would need a complete tear down and hot tanking of the block to clean it out. Since the crankshaft is scored and needs to be reground anyway, that much disassembly is about 80% of the way to a stripped bare block".

On October 17, 2011, Kelvin Dodd of Moss Motors in Southern California, USA wrote:
Don, -- Did you have an idea of the oil pressure during this problem. I've never seen a filter come apart like this and was just wondering if perhaps the oil pressure relief valve might have jammed open. -- Strange. -- I'll copy this information and save it to the Moss part number. -- It is a first. -- Kelvin

On October 18, 2011, Paul Gaylo in Corning, NY, USA wrote:
"I definitely lean toward an oil-pressure problem. If the oil pressure relief plunger in the block gets stuck, as the RPMs increase, so will the oil pressure. The pressure will grow to like 100+ psi and will easily destroy the filter. There is also a tiny port behind the plunger that, if plugged, will produce the same result as a stuck plunger".

To which Barney calls for a correction:
Excessively high oil pressure will not destroy an oil filter element (although it might explode a spin-on canister). With normal flow rate through the filter there will be only a few PSI pressure drop across the filter. If for some odd reason there was excessive pressure going into the filter housing, there is still the same small pressure drop across the filter with similar oil flow. If there was 100 PSI pressure on the inlet side of the filter, there may be 95 PSI on the outlet side of the filter element. If the filter might get clogged and exhibit a higher pressure drop, there is a pressure relief bypass valve in the filter head that will allow oil through (bypassing the filter element) with still quite low pressure differential. From the MGA Twin Cam Engineering Technical Data book, the oil filter bypass valve opens with 13 to 17 PSI pressure differential.

Considering cause and effect, it is my opinion that failure of the felt filter element ran lots of felt fiber through oil passages of the engine. Normal oil film thickness in the crankshaft bearings is about 0.001 inch. I suspect the felt fibers are considerably thicker than that. As such when the felt is forced through the bearings it will be severely abrading both the soft bearing liner and the hard crankshaft journal. Ultimately all of the felt missing from the filter had to pass through the bearings (crank, cam and rocker shaft) to get into the sump. There is high probability that some of the felt in the sump would get through the pickup screen to be recirculated through the engine more than once. From appearance of the screen in the picture, the felt clogging the screen may have been sufficient to restrict intake flow enough to reduce oil flow and oil pressure to a minimum. If fiber contamination of the oil didn't eat the crankshaft bearings, then lack of oil flow would.

Thank you for your comments -- Send e-mail to <Barney Gaylord>
© 2011 Barney Gaylord -- Copyright and reprint information