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MG Midget and Sprite Technical - Oil change using a oil cooler

Just put on a oil cooler and the thought just came to mind. When you change oil, do you just drain as usual and then put new oil in and let it combine with the older oil?
RC Bishop

Pretty much. Gives one incentive to change the oil frequently. I suppose one could dismount the cooler and drain it as well. That would keep one in touch with the condition of the radiator hoses. FWIW the oil is clean enough after a change that I can't really see it too well on the dipstick. Not that my eyes are going or anything..

R
Richard 79 1500

I hope you used a new oil cooler.... I have seen some serious engine failures with folk using a second hand cooler. Engine failure debris tends to find its way into the cooler matrix and then when fitted to a new engine, mysteriously unleashes itself on the good bearings..... :-(

Yep, change oil as normal.

Mark.
M T Boldry

I do an annual oil change with low mileage so don't change the oil in the cooler.

Exceptions for me is after running in a new engine and then every 2-4 years when I remove it and empty it.
Daniel Thirteen-Twelve

I always completely drain the oil cooler without fail, but it is a race car so is more accessible.
David (davidDOTsmithAT stonesDOTcom)

Isn't there anything which could flush out an older oil cooler properly. Parafin or similar?
Gary Lazarus

Gary yes but it's always a bit of a gamble, same as radiators, however many times you flush them some more cack always comes from somewhere...
David (davidDOTsmithAT stonesDOTcom)

Hi Mark

Many install the cooler between the block and filter housing, replacing the external pipe on the Series.

In this case, isn't the cooler before the filter in terms of flow?

A
Anthony Cutler

yes but the filter head has a high-pressure bypass valve so on cold start unfiltered oil goes round the engine.
David (davidDOTsmithAT stonesDOTcom)

OK; thought the bypass was on the block by the pump?

Is there one in the filter too (I know there's one for the old paper filter in case it becomes blocked; is this true for the canister?)?

A
Anthony Cutler

Never thought about that, I suppose when the oil is cold (20/50) there is a chance that it may be high pressure in the filter and perhaps some oil will bypass due to that pressure. However I have always assumed that the by pass valve was for filter blockage. Where did you learn that snippit David?
Robert (Bob) Midget Turbo

Dirty oil is better than no oil. And don't forget, the original small-block Chevy V8 that debuted in 1955 as a 265CID had NO oil filter whatsoever.
David "they remedied that oversight fairly quickly" Lieb
David Lieb

Bob, Steve at MED mentioned it when we were examining one of the new fancy repro screw-on filter heads, which don't have the bypass. He was telling me I should remove the ballbearing etc and plug the hole as I'm using an original one from a Mini I think. Theory is that nobody ever looks at them but usually do replace the bypass valve in the block. So if the new one in the block works at 80 psi but the old one in the filterhead has gone soft and operates at 70 psi....
David (davidDOTsmithAT stonesDOTcom)

Page 30 anyone?

Note you can't plug the long filterhead as easily as the short one, if at all. (I suppose you could get it welded)
Daniel Thirteen-Twelve

good call Daniel !
David (davidDOTsmithAT stonesDOTcom)

I used all new parts on installing a cooler. I am reluctant to loosen any connections to the cooler, as they need to be tight.
I will just replace the oil more often as I only run about a 1500 miles a year max.
Typical midget I guess,uses about a quart of oil in about 500-700 miles. No leaks but it is going some where.
RC Bishop

David,

I don't see that blocking the filter head bypass would have any effect other than possibly causing the filter element to fail. The bypass in the block (oil pressure limiter) dumps oil back to the sump, the bypass in the filter head or filter itself just bypasses the filter element to prevent too high a pressure across it and the oil ends up in the oil gallery anyway.
David Billington

The bypass valve can prevent the oil from being filtered. Most race engine builders will plug it. Some of the more recently available machined from billet filter housings for the A-series engine simply don't have that bypass valve.
Daniel Thirteen-Twelve

Daniel,

Fair enough that is the case and lack of the bypass may be OK so long as the engine isn't revved too much before the oil warms and thins. I took David Smiths' comment though as saying the bypass in the filter or filter head has an effect on the system oil pressure as though it was in parallel to the main pressure limiting valve in the block, it isn't so it can't have the effect mentioned as I understood it.
David Billington

in series David, not parallel. If the main bypass valve works first, that's fine. But if the main valve is going to open at 80 but the filter head bypass is old / soft and opens at 75 (i.e. first) then unfiltered oil goes straight into the engine, no?
David (davidDOTsmithAT stonesDOTcom)

David Smith,

No, the main valve limits the system pressure to its setting of say 80 psi, IIRC the filter head bypass pressure is much lower but its purpose is to prevent oil starvation and /or rupture of the filter element, oil pressure for the bypass valve is the pressure drop across the filter element and so different to the main oil pressure , which is a measure of the pressure relative to atmospheric.
David Billington

whatever the science - and I don't dispute it - I'm still happy to take the advice of my engine builder.
David (davidDOTsmithAT stonesDOTcom)

Curious, think we will have to go out on a limb here David B.

I too believed the oil filter bypass valve was a DIFFERENTIAL pressure valve and when David S mentioned it passing on start up I could see that with a 20/50 oil and cold weather then it was possible that the DP across the filter would be high and would pass oil. Personally I have not heard of engine builders plugging this valve, with modern oils I would not have thought it possible even when cold to get passing of the bypass but by the sound of it the people David S uses and indeed Daniel's men do seem to think otherwise. Good debate anyway!
Robert (Bob) Midget Turbo

I spoke to Keith Calver in November last year about the Billet Filter Heads. He claims that the std unit bypasses oil at about 36psi which means that a certain amount oil unfiltered oil is constantly circulating in the engine.

Take a look at his website.

http://www.calverst.com/shopopen.htm

Mark.
M T Boldry

I too think the filter bypass is a differential drop across the filter thing, and I don't feel like digging one out to check. Obviously more of a problem on neglected road engines in winter, (do you know what happens to paper elements with water in them?) but I shudder to think of pieces of filter element in the oilways.

FRM
FR Millmore

This debate could be concluded by looking at the design of the relef valve, e.g.

- is the spring pre-loaded
- is pressure measured across the filter or to ~atmos (ike the desgn in the block.

A
Anthony Cutler

Mark,

The filter bypass valve, being a differential pressure valve, it would only open if the pressure differential across the filter is 36 psi or greater which I think is rarely the case. That means that it only passes oil on the occasions the differential pressure is exceeded not continuously.
David Billington

Anthony,

It wouldn't be much of a pressure relief valve if the spring weren't preloaded. As it's fitted between the inlet to the filter and the outlet it will operate on the differential pressure across the filter.
David Billington

Well I have copied this from Calver's site. It seems he believes that it is NOT a differential valve and would pass oil continuously. Surprised at that, begining to question my beliefs now?? At the moment I will stck with the differential theory!

""Special spin-on oil filter head
£48.50
Special billet-machined aluminium spin-on oil filter head to eliminate gasket failure issues and prevent a continuous stream of unfiltered oil going to the crankshaft and bearings via the standard pressure relief valve in the filter head. Has 5/8" UNF thread for oil pipe union fitting; this is non-standard and is used to match the standard pre-injection type block union. Oil transfer pipes CST3019 and CST3021 were made for this fitment so flow restriction is minimised.""
Robert (Bob) Midget Turbo

Some info here

http://www.fram.com/carcare/techSpecs.php

such as http://www.fram.com/pdf/EngineOilFiltering.pdf

The A series is a full flow system.

Oil system valves
http://www.fram.com/pdf/ThreeVital.pdf

Could this happen with no bypass
http://www.fram.com/pdf/CollapsedCenterTubes.pdf
David Billington

In as much as there are only two passages in the filter head, namely "IN = prefilter" and "OUT = post filter", just where in hell is the dumped oil going if it is anything other than a differential bypass valve?

Don't question your beliefs, Bob.

If Mr Calver actually has some basis other than nonsense to show that dirty oil "IS" bypassing the filter, then I would suggest that a bigger filter is in order. That's how competent engine builders deal with the problem. Bill Jenkins used to fit a pair of giant truck filters when eliminating the element bypass, and carefully restricted rpm until the engine was warm. Oil and water preheaters are also commonly used. Only the larger filter is practical for "normal" use, and you still want the bypass, until the filter is about the size of a whole Spridget.

If the filter is big enough, the bypass will never open, and that answers the question implied by David S - "Theory is that nobody ever looks at them but usually do replace the bypass valve in the block" - the pressure relief valve operates most of the time, the element bypass operates only when the differential drop is excessive.

Before people start jumping on me re Calver's rep as a "successful" engine builder, I will say this:
I read many of Calver's articles last night, and by and large I find him eminently sensible and totally in agreement with my thoughts, but this one is silly.
A successful engine builder is a guy who has managed to make his stuff last long enough to finish, or maybe longer than other builders. His "success" doesn't mean he is doing everything, or even most things, in an optimum way - it only means he's got a better "package" than the competition. Race engines in particular are subject to unreasonable maintenance levels, rebuilds due to many causes which fix imminent failures that haven't happened yet, etc. And when they die, the mantra is "race engines do that". When a builder makes engines that run for years without failure, then you have a master builder. But it can be argued that a race engine that lasts longer than the race is overbuilt, hence too heavy, therefore slower than otherwise possible. Catch 22.

Jim Boffo used to run a Cooper S in SCCA at national championship winning level, and told me that all internal parts and clearances were at book specs, and, he ran it three seasons without taking anything apart - never did anything from year to year other than standard tuneup.

FRM
FR Millmore

I know Keith as a personal friend and will say that MOST of his thoughts are good, however, like most people with some authority behind then, some statements may be taken as fact whereas they may not always be the case.....

Mark.
M T Boldry

Swiftune sell the billet filter heads without a bypass also and say "No bypass valve so only for cars with an oil cooler or flexible pipe.". I have to ask WTF does having an oil cooler of flexible pipe? have to do with it.

http://www.swiftune.com/Product/358/swiftune-billet-oil-filter-housing.aspx
David Billington

LOL.
Robert (Bob) Midget Turbo

The oil stays cold longer, giving you a better chance of blowing the element apart, so you will buy a new engine or bits! But "race cars blow up".

FRM
FR Millmore

FRM,

That may be right, thanks for your previous post, I think you summed up quite eloquently what I was trying to convey in a few previous posts.
David Billington

Yes - agree with all comments along lines of DB; we have a full flow system; easiest pressure regulator is differential (and that's what it needs to be anyway to protect the filter medium); only under extreme conditions would this by-pass need to operate.

A
Anthony Cutler

I may just be lazy & haven't looked through all the threads but i really don't see how the pressure of 36psi was measured without the use of a differential pressure gauage (expensive piece of kit) & take off's to suit which don't exist on the standard filter head.
Brad (Sprite IV 1380)

My view coming into this a bit late... is that it's simpler to tap and plug the bypass in the filter than to fit a bigger filter.

Of course David Vizard advocates the use of a big oil filter to prevent oil being circulated without being fitered. At the time he wrote that I don't think it was common practice to plug the filter head bypass and of course on the long filter head there is insufficient metal to tap so it would have to be welded.

The bypass valve is there to prevent oil starvation for a completely and utterly blocked oil filter I guess but like the warning light for a blocked filter it's redundant for owners who regularly change the filter and want the best for their car's engine.
Daniel Thirteen-Twelve

This thread was discussed between 16/07/2009 and 26/07/2009

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