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MG Midget and Sprite Technical - Arnold F/Stein

I am quickly losing patience with my oil leak at the rear of the engine.
With a turbo fitted there is a lot of oil dripping out

Arnold I think you encountered similar problems and may have cured them using evacusump system. Can you comment please

Or anyone else for that matter.
Robert (Bob) Midget Turbo

Hi Bob
As you know I have a major oil leak that is coming from the bottom of the bell housing, now I have removed the engine and gearbox I am putting an extra breather on the sump as when I put a breather on the dip stick it did improve things under normal load, but as soon as I give it any stick it comes gushing out again.

So have you tried an extra breather or two? dont forget these turbo engines like to breath.

Is your oil coming from the bell housing, could it be gearbox aswell ?

When you replaced your clutch was there any oil on the release bearing, this would point to gearbox leak.
Rob Newt

Hi Rob

I have 2 large breathers

I have a 22mm breather on the old dissy hole (I have programmable ignition now). Also I have a 15mm breather on the timing cover and rocker cover, this is connected to the manifold suction via a non return valve so experiences suction when not on boost.

However when idling the engine is oil tight but under stick it pluthers out. I fear the only way to reduce this leak is to find some vacuum on full load. That is the function of the exhaust evacusump but I was ondering how much suction was actually created?
Robert (Bob) Midget Turbo

Hi there

I did a lot of experimenting on this oil leaking. In the end it worked to have two 22mm breatehers in the sump, one on the timing cover, one on the rocker cover. I use the PCV and a evacusump to keep up vacuum under boost. I also use an oil separator to oil in the combustion (be careful lowers the octane number).

What else can I tell? engine is not completely dry but ok for me. Please remember that the vac won't keep the oil in, the breathing does!
a.o. arnold

Should have mine back together in about a week or two so I will keep you posted if the extra sump breather worked or should I be putting two on now?
Rob Newt

How big was the pipe in the exhaust please Arnold?
Robert (Bob) Midget Turbo

Bob this issue has been solved countless times by proper designers on every production turbo engine. Pick up a Haynes manual for a Metro or Montego turbo and see how they did it. Not rocket science.
David Smith

C'mon! Really?
Do we need this?
Trevor Jessie

whenever we modify our cars it pays dividends to look at how similar/same problems have been solved elsewhere - it seems daft to reinvent the wheel and give oneself so much grief when it doesn't work as intended.
David Smith

Not to worry Trevor David is no problem a little gullable yes problem no!

David correct me if I am wrong but as I understand it the Metro turbo venting worked in the following manner

From the inlet manifold a non return valve allowed suction to the engine breather when a vacuum was available in the inlet manifold(off boost). During boost conditions this vacuum becomes a pressure thus closing the non return valve (this is refered to by some as a PCV) During these times a second valve opened that tried then to make use of the extremely slight vacuum available at the air filter inlet (before the turbo).
The Metro turbo operated at a mere 5psi of boost and the engine rear seal was a far better design than the non existant Spridget variety.

Is this correct or have I missed an important bit of technology?
Bob Turbo Midget England

I'm interested in a genuine discussion of the issue because I plan on building a turbo system in the near future. Currently, my supercharged engine does not have a problem with oil leakage, but it is only producing 9 psi.
Trevor Jessie

Theory correct, vent to inlet manifold on overrun and vent to air filter enclosure under boost. Don't think there's two valves Bob, the one I know from the Monty turbo (and believe same or similar part on Metro) is a 'flip-flop' valve with one input and two outputs. Used on other turbo cars too back in the day, Turbo Technics used to keep them as a stock part. It's also important to have an oil droplet retention device in all breathers otherwise you may get a lot of oil deposit in induction system, pooling in bottom of filter enclosure is not uncommon. Small in0line metal gauze filters are useful for this.
How do modern petrol turbo engines arrange breathing? Or is it the case that tolerances are so good now that there's hardly any pressure in the sump?
David Smith

Yep David I thought I was right (it does happen occassionally) Anyway the 2 valves I refered to were the PCV and the flip flop as you refer to it which is essentially a non return valve. It needs to be a non return valve otherwise when the engine was off boost the line to the air filter would simply be a bypass around the carb. :)

Anyway for your info I have recreated that system exactly on my car. With boost at 5 psi the engine is fine but with boost at more than 20 psi the system is totally inadequate and hence the need to find a better suction solution during boost. I also have oil seperators fittesd to the breathers that I fabricated myself.

By the way I have owned a Monte turbo for a number of years plus 2 Metro turbos, one of which I sold only a year or so ago. :)

I think a solution to this problem is to have some sort of air pump to evacuate the enine when on boost to substitute for the lack of manifold vacuum. I am wondering if the USA type emmissions pump would be something that could be used?

Has anyone any info on that pump please Trevor maybe?
Robert (Bob) Midget Turbo

Bob,

Thinking outside the box a bit, what is the condition of your engine, in particular your rings? If they are worn then the positive crankcase pressure will increase I assume? I'll speak to the old man and see what boost pressure he's running on his Maestro Turbs.

BTW see you friday at the H&J

Steve
Steve H K-ser

Steve

Yes mate that could be the case and with the engine being recently rebuilt perhaps as it beds in it could improve.

Anyway will see you Fiday, by the way you won an MGCC Lincs award at the annual dinner for your autotest efforts at East Kirkby, Jeff picked it up for you. If he has not delivered it yet then I will contact him and get him to bring it along.

Robert (Bob) Midget Turbo

And the funny thing is, the autotest was done in my Dads Maestro Turbo! :)
Steve H K-ser

BTW Bob when I was talking to P.May regarding my oil leak, he told me of an MgB engine he rebuilt that leaked For 2000 miles then suddenly just stopped !
How many miles have you done on the rebuilt engine ?
Rob Newt

Sorry, I have no knowledge of how much vacuum the emission pumps pull. Given how they were configured I can not imagine that they pulled much vacuum.
Trevor Jessie

What dtails do you have on them Trevor
Fitment etc?
Robert (Bob) Midget Turbo

Dont know if its particularly relevant, but a Spridget racer at Mallory last year had a DIY evac system fitted to his engine to help overcome excessive oil consumption. I cant recall his name but he races a class C / 'roadgoing' car usually in the MGOC series and he was giving the MGCC series a try. From memory, it was based on a pond pump.
Doug Plumb

Having refreshed my memory of the information by Vizard I have decided to give the evacusump a try. If it is as good as David describes it ought to solve the problem. Will let you know.
If it doesn't work then I will be looking to fit the american emissions pump.
Robert (Bob) Midget Turbo

Evacusump is probably the way to go Bob,just watch you don't pull all the oil out of the engine as well!(it has happened)
steve cowling

Made the pipe for my evacusump

Robert (Bob) Midget Turbo

Welded it into my exhaust pipe and pipe fitted back onto the car.

Didn't test it today as the weather was atrotious and I don't like putting dripping wet cars into my garage.

Tested the pipe when the engine was ticking over and I thought I was getting a bit of pressure? Hope that when the car is travellin at speed exhaust will create desired suction.

Robert (Bob) Midget Turbo

Hi Bob,
just replumbed my evacusump for the new engine, email me if you want some specifics, i'm a bit busy with other projects at the moment.
RS
Brad 1380

Bob
Just test done a test drive.....

it has halved my oil leak after fitting extra 1/2" breather to the sump,under normal driving conditions no leak at all not a drop!!!
So now I can live with this and sleep at night, no more reading Vizards book into the early hours.
How you getting on with your evacusump or have you already fitted a k series !
Rob Newt

OK I have my evacusump connected and I think the leak has lessened but is still there.
However in the meantime I have developed a fuelling issue which is preventing me doing any more than a couple of miles before it cuts out through lack of fuel

Think the fuelling issue is vapour lock so need to sort that and then give it a try. Unfortunately my MGF had a starter motor problem so that has occupied me for a couple of nights but will hopefully get back on my midget shortly.

By the way getting the starter motor out of an MGF is a nightmare :)

Anyway I was cycling home from work tonight and thinking about things (Great way to consider problems is getting on your bike) and I suddenly thought is my main breather clear?

I had fitted a 22mm breather to the old dissy location and I suddenly thought to myself that I don't think I have removed the original drive spindle!!! That I will need to check first thing at the weekend.

I could be heading for idiot of the year!!
Robert (Bob) Midget Turbo

I know this sounds extreme... but you know me...LOL

But what about gap-less piston rings???, at the end of the day, thats what your battling "engine blowby from worn out rings"

Trevor jessie knows of a company where you only have to replace the 2nd ring... I cant remember the name of the company... But Im a fan.


Prop
Prop

Bob -
"I thought I was getting a bit of pressure?"
There should be a check or "anti backfire" valve in the line from the exhaust to the engine. That keeps positive pressure from getting to the engine. Also "If this item is not put into the system, the engine can easily experience a sump explosion if a backfire takes place." - DV
Maybe you have this but....

Not entirely clear to me, but have all of you using these things now blocked off all those breathers? That would be a requirement of a true evacusump system, though I suppose there might be "half & halfs".

FRM
FR Millmore

Here ya go Bob,

http://www.jegs.com/i/Moroso/710/25900/10002/-1?CT=999

Remember you have to have a free flow exhaust other wise the back pressure will activate the gulp valve ... (large PVC valve) I want to say the gulp valve needs to be able to flow 17 to 20 CFM to be effective, But Im reaching into the back of the brain noodle for that tid bit of info

Prop
Prop

the kit shown by prop is the way to go. You need a Bernoulli effect to get suctio from the exhaust (similar to a carb sucking in fuel). I my case in only starts to work at higher RPM's
a.o. arnold

Hi Arnold and others I have installed mine as described

I have a pipe welded into my exhaust in such a manner that it is experiencing suction as air passes along its length, do you not think this will have a "Bernoulli effect"? See images in above posts.

I also have a non return valve so that connection to the breather system is only available when pipe is under suction. Think that ought to be fine?
Robert (Bob) Midget Turbo

I think you got it bob,

to get the Bernoulli effect you need to have the angle of the pipe at 40 to 50 degrees... which looks really good in your photo and the radius looks nice and tight to create better suction, and I think the pipe size dia is a good size...Hook up your gulp valve and your ready to go... where Are you going to hook up to at the engine side?

On my moroso kit instructions... like the kit I showed you, the shorter the path from the ex pipe to the engine hook up the better the suction

Curious tho, Ive wondered from time to time ... if you have loops and arcing bends in the hose from the EX pipe to the engine hook up... will there be drops in suction, ive noticed this on shop vacs with small dia vacume hoses esp with longer hoses... it seems the same would apply in this secnerio

Prop

Bob,
just had my engine spew out oil at high rpm, the evacusump works fine at low rpm, but from around the mid point i can feel pulses coming back up to the non return valve. I have used the weld in adapter supplied with the kit, though i think i may change it to your design as theres less chance of pressurising up the hose.
I run a Jolt system too so have taken the evacusump feed off from the old dizzy location.
I might do as Arnold says & put some 22mm breathers in the sump, i guess they need some sort of valve on them to stop the evacusump breathing outside air in.
Anyone know where to buy 22mm weld in bungs & valves?
Brad 1380

Made a new exhaust adapter using the supplied bit (you get two of everything as its for a V8) & adapted to Bob's design with a pipe angled down the exhaust. Looking at the old adapter it is ever so slightly canted into the exhaust stream so i think that was the cause of the pulsing.
I'm also putting a large breather into the sump too complement the rocker cover, dizzy take off & timing cover ones, hopefully that should be the end of it.
Brad 1380

That's it Turbo is going to have to come out what with fuel problems but more importantly oil leaks abound I think my 1400 NA will need to go back in so I can happily do the Midget 50 LEJOG.

Anyone want to buy a turbo engine and ancilliaries?
Robert (Bob) Midget Turbo

Bob,
how are you going to plumb in the 1400? are you keeping the evacusump system?
Brad 1380

Yep I think I will and before I put it in I will add a breather to the sump. Think I will not bother with the rear seal. I feel that is not helping with the problem?
Robert (Bob) Midget Turbo

Just put a 28mm breather in the sump today, had to use an Oxy set to get enough heat into it to braze the fitting, also fitted another smaller fitting low down for oil drain from the catch tank. I've used the other oil strainer from the evacusump kit for the sump breather, hopefully get it all plumbed up tomorrow.
Brad 1380

Keep the faith Bob,don't give up on the turbo - life's too short!
Brad,I have the breather setup you describe,the oil drain back to sump is well worthwhile,oil definitely comes over,as I found when I pulled mine apart.
steve cowling

Steve did you put a one way valve on the return to sump line?
Brad 1380

No,Brad,just a small 6mm? flexi from the bottom of the tank to the top side of the sump.There is a big line from dizzy hole to tank and another to atmosphere.The tank is sat on the chassis rail.
steve cowling

Steve, i put my oil return bung low down on the sump as i didn't want it to turn into another breather, the valve operates when the tank is about 1/2 full.
My catch tank is just an old Tudor windscreen bottle, but if this set up looks like it will work i'll get something better fabricated.
Brad 1380

Bob

You could try Prop's suggestion of gapless rings - its something we used to do years ago on the Metro Challenge turbo engines - doubt they used quite the boost you do however. I've not had anything to do with an inline turbo A series so can't comment further, other than to say that if you need any assistance refitting the rear oil scroll drop me a line - I'm quite good at doing that - haven't had any rear main leaks from any of my (atmospheric only) race engines...

Good luck

James
James Bilsland

There is a guy in the states that "rebuilds" the surface of the that scroll cap with metallic epoxy (JBWeld). I do not know the exact procedure, but it involves cutting a groove to hold the epoxy and some sort of thin material to create the clearance while it hardens. Then the new surface is back to the tightest spec.

Many people swear by this technique. I was fortunate to have mine fitted by the machinist when he did the line boring of my block. So far, no leaks to speak of.
Trevor Jessie

James I'm interested in any advice on refitting scrolls as I'm about to pull my engine apart and renew bearings etc.
steve cowling

James I may give this one more try but I would need a couple of weeks or more to re install a decent 1400 to do Midget 50 lejog so must make a decision soon. Will seek advice on the rear seal shortly!
Robert (Bob) Midget Turbo

Had to change the one way valve from the catch tank as it was a push fit & leaked so now have a proper S/S bulkhead free flow fitting for return to sump.

The Evacusump system still pulsed back up the pipe even after welding in a pipe similar to Bob's (though at tick over it gave better suction), i have a free flowing exhaust but its obviously still too restrictive, so i have blanked off the Evacusump exhaust fitting as i can't get it to work through the whole rev range.

Now the engine has 1/2" rocker, 28mm sump, 3/8" timing cover & 3/4" dizzy breathers, thats a lot of hoses going to the catch tank, hopefully that will be it breathing properly now.
Brad 1380

Hi Brad,
I have 28mm dizzy,15mm timing cover and top cover.It's ok for normal driving,but after arun up the strip,say 15 seconds full throttle,there are always one or two drips on the sump from front and rear sumpseals.
steve cowling

Do you still use a PCV? I was allmost desperate and considered to use an electrical air pump (used in diesel engines) to ensure vac in the crankcase. You could give it a try, but I am pretty sure if all this venting does not help, something else is the problem
a.o. arnold

What do you guys use for your breather hoses? I've got some silicon hoses, but they are very thick walled and so dominate the engine bay. I'd have thought some thin walled wire reinforced convoluted stuff would be good enough, but I can't find any in various sizes anyway. Maybe I'm not looking hard enough.
Tarquin

Tarq, basically what ever i've got laying around, which isn't too much at the moment after several rehashes on the breather front.

Can anyone recommend a catch tank fabricator?
Brad 1380

Arnold that has cheered me up

""I was allmost desperate and considered to use an electrical air pump (used in diesel engines) to ensure vac in the crankcase""

I thought everyone else had just a tiny leak, hopefully if everyone else has a torrent then we can all help find solutions.

I too had thought about an extra air pump to evacuate the crankcase. I thought about the emmissions pump from a USA spec car but struggled to find information about them
Robert (Bob) Midget Turbo

I'll be going for a run tomorrow Bob, so will let you know how it goes.
Have you tested your Evacusump system for pulsing?
Brad 1380

Yep I have felt the end of the pipe with the engine reving in the garage and it does seem to pulse. Dont know what happens under power runs but I think sometime I will have to measure it with a gauge.
Robert (Bob) Midget Turbo

Bob, I never updated you on the USA emissions pump. I looked for a working example and could not find any locally. The one that was on my car when I got it was making noise and did not seem to be functioning and thus it was trashed. Such is the story with most everyone else. They do sell them remanufactured as some states still require the OEM emissions.

I still wouldn't expect them to create much vacuum even when in new condition. If so, I would imagined that people would have been using them for brake boosters on hotrods that are boosted.

On a side note, the midget's wiper system and variations of it are very common in streetrods.
Trevor Jessie

I brought this up before, but nobody answered.
Why are you fitting evacusump systems and leaving all those breathers open?
Per DV and others, "For the system to work effectively, the engine must be virtually airtight....Most engines will hold 15-20"H2O vacuum before air starts to leak in past the seals.... all vents save those associated with the evacusump must be sealed."
That would be the PCV to inlet and the connection to the exhaust. And note that back pressure in the exhaust also makes it not work. The crankcase should then always be under vacuum, and if it is not, you have a blowby problem, which may be unavoidable at high boost if the cylinder walls are flexing.

FRM
FR Millmore

Bob,

Is the section of pipe you welded the suction tube into the same diameter as the rest of the exhaust system?

I would think it would work better if the section with the suction tube were a smaller diameter than the rest of the system, for example a 1 3/4 inch setion in a 2 inch system.

I don't know if that will insure negative pressure all the time, but the smaller setion should at least have a lower pressure than the rest of the system.

Charley
C R Huff

Well the engine is almost oil tight now, just a small drip from somewhere which i can't find as the oils new & too clean. Still its better than having the catch tank overflowing over the exhaust & filling the car with fumes.
So in my opinion Evacusump just doesn't work on a road car with a silencer, a racer maybe.
Just need to make a better catch tank now.
Brad 1380

This thread was discussed between 30/01/2011 and 10/03/2011

MG Midget and Sprite Technical index

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