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MG MGB Technical - Oil Filter - Message for Tim Jenner

Tim
I saw your query/letter in a the latest issue of one of the classic magazines. Did you feel that it was a valid answer as they focused on the vioscosity you were using and not the root cause of the drain back valve IIRC? I think you you did a better job of resolving it yourself with the experiments on the different brands.
BTW if I can be cheeky, what were the recommended filter brands as I have just got my engine running again and noticed a huge delay in pressure buildup so need to get a decent unit.

Thanks.
Martin

Hi Martin,

Actually, I thought their answer was useless! Editorial cutting removed most of the detail from my letter as well so it was a bit irrelevent in the end. However...

As you may have read in some of the threads I had on here a while ago, the root cause is that the anti-drainback valve in certain filters have changed and no longer seal adequately. I tried Champion C102 (until this year, my standard filter - never had a problem) and Unipart GFE121 filters and both had the same problem. Spoke to Roger Parker at the MGOC, who took the matter up with Unipart and found out that they HAVE changed the valve and will now no longer even refer to it as an anti-drainback valve (because it doesn't work any more). It doesn't look like it's related to oil type, though thinner oils are probably more likely to leak past a marginal quality valve. Possibly the change is an industry wide trend, or more likely the Unipart and Champion filters are made in the same factory. Roger promised to try to find a suitable substitute for the club to supply but I have not heard anything since.

The upshot of all this is that I am currently using a new-old stock Coopers filter (can't remember the part number, I can look it up if you want) which I found at Epsom autojumble. Coopers are the same as Fram filters, which are more common and you should be able to find one at a motor factor somewhere - this presupposes that Fram haven't also changed their valve in recent times! I currently get almost instant pressure after standing overnight, and no more than a second's delay after standing for over a week. Not as good as the old Champion filters I used to use, but a hell of a lot better than the new ones! The best way of testing them (apart from putting them on the car) is to find a bolt the right size to seal the centre hole (the outlet from the filter). Fill the filter with oil, seal the outlet with the bolt and invert the filter over an icecream tub overnight to see how much oil leaks out.

Hope that helps - if you need more info (part numbers, etc) let me know.

Cheers,
Tim.
Tim Jenner

With the ongoing problem of oil filter drain back valves, isn't the final solution to get an adaptor that mounts the filter up the correct way. Moss (USA) list one for the MGB.

Mick
M F Anderson

Tim
Thanks for the detailed answer. I thought that they had pre-supposed too much and had come up with a less than helpful answer. Obvious space constraints in magazines do unfortunately mean that this happens, and I guess the gurus that answer these queries are not always as familiar as the one make specialists. It would be nice if they passed these enquiries to the specialists.

As to mounting the filter the other way around, on the 1980 model that is impossible since the starter motor gets in the way. I would have thought an inline drain back valve in the oil cooler pipe next to the housing might have improved the situation, or indeed between the block and the hose so that the cooler etc all reamin full. I know that the filter is below the level of the hose as it passes through the radiator shroud on the later cars, but I suspect some syphoning occurs as the oil drains back, thus emptying the entire section.

I have a thin Penrite running in oil, and after a night, it took 5 seconds which is not good.

Thanks again, Tim.

Martin
Martin

I had silmilar problems with a Unipart and have now changed to Volvo part no. 3517857, as suggested in a previous thread. The oil pressure now builds up immediately
C Atherton

Hi All,

This subject has long puzzled me and I have never had problems of oil drainback using the inverted filters as fitted to later Bs.

The oil is pumped from the sump - it cannot drain out of the pump when the engine stops as the pump inlet and outlet are both at the top of the pump - so there must be oil in the pump at start up.

The oil goes from the pump to the oil cooler and back through the filter one way valve to the outside of the filter element - again, since the connections to the cooler are higher than the cooler, the oil cannot drain out of the cooler, so we have a full oil pump and a full cooler on start up.

The oil passes through the filter element from outside to inside and then down the vertical central tube to the main gallery and then on to the bearings - so the filter should be full at start up.

The only place that oil can drain away is through the bearings and it is only under the head pressure of a few inches from the filter ( the highest point in the supply system) to the bearings. If the clearances are OK then I doubt much oil can get through - capilliary action probably balances static pressure.

OK so there must be some siphoning going on somewhere - and air has to get into the system to allow this, so where does it comes from?

Possibly the rocker gear, if worn allows sufficient air into the top of the oil passages - unlikely, because it has an intermittant oil supply regulated by the rear cam bearing. So is air getting in via the main or rod bearings? Depends on engine condition.

So perhaps the answer is that oil draining out of your filter is a symptom of engine wear and not really the problem to be solved! This would also explain why the Unipart filters work OK on newly rebuilt engines with their close clearances!

Unless anyone knows different.....??
Chris Betson

Chris,

You clearly know far more about B's than I do, but from experience I also suffer from this problem. My engine is 3 years old, and doesn't puff any blue smoke at all.

I had a Purolator filter on when I bought it and I got instant oil pressure from start up. I changed the oil and changed for a Unipart filter. The oil pressure took so long to come up it was scary. I then changed to a Fram filter which was marginally better, but still total crap.

I have now stocked up on Pipercross oil filters and I once again get instant oil pressure.

Will be sticking with Pipercross from now on, and the Unipart filter was not OK it was crap, on a new engine!
joseph phillips

Gentlemen - For what it's worth, here is a link to a fairly comprehensive study done on various oil filters available on this side of the pond. I have used the Wix filters for many years with good results, but I don't know if they are available (perhaps under a different name) over there. Cheers - Dave
David DuBois

Haven't had much luck with Fram filters...

Steve S reckons the K&N Gold is the best he has used, but i have not seen that for sale here in the UK.

Joeseph

Where are the Pipercross ones sold - model/part number perhaps? That is if you have them to hand...

My oil pressure is not as instant as it was, but i figure engine wear to be a factor - even so, i have found that picking and choosing ones filters carefully can lead to better (or worse!) results.

~PHIL
Phil

I honestly don't think engine wear is the issue here - mainly down to the fact that I had no problem at all until I changed the filter. Different brand, problem solved. My engine is also, to the best of my knowledge, in not particularly worn and had a new head a couple of years ago. If it helps, the Coopers filter I'm using is a Z27A and I have seen several of these new-old stock at auto jumbles over the past few months.

Tim.
Tim Jenner

I don't refute that there is evidence that points to the filter being the culprit - I just don't understand the mechanics ( or hydraulics!) of the process.

My simple mind says that for oil to drain out of the filter, air MUST get in, and I don't see how it does unless it comes from the main oil gallery into the centre of the filter and the oil escapes past the anti drain valve through the oil cooler and the pump, back into the sump.

And if the air is coming in along that route, it must do so through the clearances of the bearings or, possibly, through a badly seating oil pressure relief valve.

Perhaps the solution is to return to the original design of the filter element in the upside down can and replace the clunky old starter with a new high torque unit which is much smaller.
Chris Betson

I gave up trying to understand too deeply a long time ago! :) But I agree with you, Chris, it's an odd one...whether we are fixing the problem or the symptom, finding a decent filter is certainly a good move. When you talk about the "original filter" I assume you're referring to the Teclamet paper element. I guess these must have had the same problem - was there a drainback valve somewhere other than the filter housing on these?

Tim.
Tim Jenner

Chris
My unit is freshly rebuilt, just completed the cam burn in and about 20 road miles. I do have the Penrite Running in oil in the engine at present so that maybe a factor as it is thinner, which was the answer given by Practical Classics in their response, but this is shortly due to be replaced with 20W50.
If nothing else a strong case for the switch back to a hanging filter would be a much cleaner oil filter change! Although I suspect the mess the oil makes is all part of the grand chassis anti-rust plan formulated by the Leyland engineers!

Martin
Martin

Just went back and read my post (much to my embarassment) and found that I left off the link. Here it is:
http://www.frankhunt.com/FRANK/corvette/articles/oilfilterstudy/oilfilterstudy.html
Cheers - Dave
David DuBois

Tim,

The original filter housings were bolted directly onto the block and hung downwards so the only bit of the system that could drain back would be the oil galleries.

So a downward facing spin on filter adapter, as sold by Moss for the MGA engine, would allow the modern filter to fit in the original orientation and drainback should be eliminated.

The only issue is then starter motor clearance.
Chris Betson

From memory, doesn't the steering column get in the way as well?
Tim Jenner

Tim,

No, there is clearance for the column.
Chris Betson

This thread was discussed between 16/07/2003 and 17/07/2003

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