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MG Midget and Sprite Technical - Fixing the leaks, catch tanks

Due to my finger injury which is largely still healing and my thus inability to do any serious engine-out work on the car, I am consigning myself to coming up with some practical next steps to my oil leak problem, which I posted about a while ago and still haven't solved. I am not driving the car anymore as it really does lose a considerable amount of oil per even a small trip.

At the moment I have a the normal breather connected to my HIF vacuum, a sump breather venting to a K&N behind the grill, and a rocker breather venting to a K&N right above it.

I have a feeling that these may be part of if not all the problem. I would like to think that a catch tank may solve some of my woes as it's a bit of work I can reasonably do with my screwed hand!

Am I right in presuming this and if so, which catch tank should I get? There are many and I can't see the wood from the trees. Fabricating is out of the question at the moment, I don't have the dexterity or the tools!

Thanks in advance.
Rich Amos (1330cc Blaze Red '72)

Yeah your breathing to atmospher....meaning its a 1:1 ratio...So because of the blowby in the piston rings your getting positive pressure in the engine at higher rpm, ...meaning your oil is looking to find a way out of the engine ....sort of like when you pump up a garden spayer with liquid in it, what you need is a neg. pressure inside the engine...thats the theory anyway

I cant help you with the "practical" of fixing the problem as I dont know much about single HIFs...Im guessing its a HIF6....there is some stuff in the archives,,,but others will be along soon.

Any thoughts or ideas on the following.....

I have been kicking the idea around of hooking up an electrical vacume pump with an adjustable valve,In order to control the amount of pressure it sucks out of the engine. I was thinking of hooking it to the metal blub that used to be the fuel pump area on the block.

prop
Prop

For catch tanks, shiny expensive aluminium ones looks great, but a plastic oil container works very well and can be found on a few race cars here.
In your case Rich, a 20 litre oil container or perhaps fit a return line to the engine?
Mike Allen

Rich,

Think about the standard set up, air is vented into the engine via a small hole and filter in the oil filler cap, the suction is created by the feed into the carb/inlet manifold. As Prop says you are letting too much air into the engine so there is no vaccuum in the crankcase, so any blow by will cause an increase in crankcaes pressure, ie leaks. I am sure the A sries is designed to work with negative ( vaccuum ) pressure in the crankcase. Try blocking up 2 of the breathers you have and leaving the one to the carb.

I have a HIF carb on mine and never have any serious leak problems.

Mike.
M J Pearson

I'd have thought blocking up breathers simply forces the remaining breather to work harder.

The idea of a crankcase breather(s) is to prevent a build up of combustion and exhaust blow by gases remaining in the sump, at pressure.

A catch tank will not prevent oil loss - it simply collects oil that would otherwise be deposited out of the breather filters or via the exhaust (if the breather goes to the carbs).

It's not that expensive to have AH fabrications make a bespoke oil catch tank of a size you require. The main think you need to consider is how many inlets do you want and whether push fit or threaded fit.

An empty 1 or 1 Litre milk container can suffice for many years.
Daniel Thirteen-Twelve

Thanks for the comments so far

Honestly, I'm just trying to get a gauge of what I should do with these breathers - block them, catch tank, anything else? I know little about the breathing science... but something tells me that a 7k mile engine shouldn't be leaking so much so soon.

These breathers are the only difference since rebuild so in my eyes it tends to point to the problem!
Rich Amos (1330cc Blaze Red '72)

I got to agree with you rich,

try blocking those breathers off or redirecting them back into a vacume port....

look at vizards book, he has a system with a gulp valve that hooks into the exhaust system....the more rpms the more neg. pressure is created in the engine, as the exhauste creats more of a vacume the faster it goes.

prop
Prop

If the oil is leaking out of the rear main seal, fitting a catch tank will be of no benefit.

You need to reduce the crankcase pressure, so you need vacuum. No catch tank I can think of will produce this, no matter how shiny or expensive.

Try joining all of the breathers together and then connecting to the carb.
Dave O'Neill 2

Thanks Dave, exactly what I wanted to hear. I will attempt this to start with and see what I get.
Rich Amos (1330cc Blaze Red '72)

I like what Dave says.

Positive pressure is caused by poor retention of piston-caused compression. the more breathers you have the more opportunities for spewage. The more breathers you have the more difficult it will be for any line to the intake system to create vacuum. All breathers should be connected to vacuum, none open to atmosphere. I think.
Richard 1979 1500

These are all band-aids on a hemorrage. If you are spewing that much oil you are just going to mask a serious situation. Also, you will be burning the oil which will keep it off the garage floor but it is still disappearing from the crankcase. Oil is not an efficient fuel so plug fouling, poor running & emissions failure are all definite possibilites. Hate to say it but I fear it's time for a rebuild.
Mike G

AAAaaahhhhh Mike,

Your such a killjoy, Of course your correct...but who wants to hear that. Far better to pretend that nothing is wrong, I spent 20 minutes in my living room earlier today, pretending my car still ran, and I had an enjoyable ride, driving thur the back country roads, looking at thhe fall foliage...granted it was all make belive, but hey thats the life of a midget owner....LOl 8 ^ )

prop
Prop

Rich, I too have a similar problem, and like you I have been trying to find a solution(I have lost count how many threads I have started and looked up on this subject)
I have a similar set up, 1275 with a hif44 carb. Breather from the timing case and a breather from the mech fuel pump boss. Ive tried both breathers venting through K&N filters to atmos, Still leaks. Ive tried venting timing breather to the carb and the other to atmos, still leaks. Ive tired joining both breathers to a tee, then to the carb..and still leaks but not as much. Also tried venting both breathers via a plastic home made catch tank then to the carb...no change, and no oil caught!
I can remember when I had twin carbs with the two breathers venting to the carb and it behaved quite well.
Seems like all the problems started when I fitted my new shiny big single carb!
I have even pulled the engine and fitted a new seal on my rear crank seal conversion I did years ago, and still oil is passed. Im not convinced its the seal, im sure the crank pressure has a big factor. In fact Ive just got back In from my garage with an idea.. could it be by some chance that im trying to vent too much with the added mech fuel boss breather, could this be upsetting the balance, that with my twin carb set up seemed fine?
I dont know.. any ideas?
If you happen to sort it id love to know the answer, and if I have success Ill let you know.

Ian
i coxon

Ian the frustrating thing is that I had a leak before the rebuild, however this was due to blowby as the car was running lean on the new HIF44 (air leak in manifold), which then caused the rings to go among other stuff.

So now, I have a brand new engine that after 6k just pissed oil, to the point that it's constant. My only solution given your experiences, I presume is to totally rip it out, replace all seals and block the auxiliary breathers.

Frustrated.
Rich Amos (1330cc Blaze Red '72)

When I built my 1215 and 1420 A series I fitted 2 large bore, 1" ID breather pipes into a catch tank and that worked for me, one from the fuel pump boss and one from the rocker cover. No rear seal just standard scroll, the idea being minimal resistance to gas flow so minimal pressure build up in the crankcase. The system did let oil vapour past but oil leakage was negligible.

Now a few months ago a thread mentioned problems like this and like Props idea I semi seriously suggested the likes of one of those "electric turbocharger" units on ebay but used to suck gases out of the crankcase. For the application I would expect a fan/blower capable of shifting a large volume of air at low pressure would be worth trying.

I also don't subscribe to the idea that the A series was designed to have negative crankcase pressure, at least not initially only later when emissions concerns came in , as the early engines vented straight to atmosphere. I had a 1098 fitted with a 948 tappet chest breather and that worked OK but the engine was worn and I found out that the vortices in the engine bay vary according to speed, going down the M4 at 70 left a battleship worthy smoke trail, dropping to 55 didn't, it effected whether the ejected oil ended up on the exhaust manifold to burn off.
David Billington

Rich, I totally know how you feel, frustrated is definately the word, especially after you have your new engine,and the problem is still there, but then surely that must point to it being a different cause,(since now you dont have excessive blowby etc)so I shouldnt pull the engine just yet.
Have you tried venting your two K&N breathers to the carb,just to see if that does make a difference, I know it hasnt worked for me, but if i remember correctly the frontline instructions for the rear sealkit says that if you have a newly built engine it wil most likley cause oil to pass the rear seal, and to vent from the sump or mech fuel boss to a filter or the carb. May be worth a go.
Im going to try basics, and try just the original timing chain breather, with a good diameter pipe,( currently its approx 12mm, stepped down to about 8mm to fit onto the carb.)and blockmy additional vent. Then I may even try fitting my twin carbs just to satisfy my curriosity.
My engine is a gold seal with pretty low mileage about 17500 miles , and doesnt burn oil, and sucks at the oil filler cap quite nicely,so Im not convinced its worn , so im sure its breather related.

Is it possible to vent too much, to cause leakage? Any one know?

Ian
i coxon

Ian,

I don't think you can vent to much but Vizard covers things like this and IIRC the bore diameters you are quoting are insufficient to properly vent a tuned engine. Basically 8mm bore pipe just won't flow enough to provide the desired crankcase depression.
David Billington

engine is almost out!!!

I got my engine Half way out tonight,,,,just 1 more bolt on the exhauste, the tranny bolts, the engine mounts and the starter....and she is out of there....one of the benifits of pulling for the 7th time...it goes fast...only took about 45 minutes to get this far.

When I build my engine in the next several weeks, Im going to build a dyno stand out of wooden 2x4's so to test and break in the new engine....after I get 500 miles of of engine time sitting still so I can break it in and check for leaks...then Im going to install it back in the car


prop
Prop

I agree with comments: block up the extra breathers, use the proper cap on the rocker cover and bring the system back to standard. As stated several times above, the engine / scroll are designed to work with a vacuum - remove the vacuum and you WILL havea leak.

My 1275 used to leave a very occasional tiny spot on the garage floor... that was oil-tight enough for me. (Take of the breather and the oil would dribble out ~continuously when hot.)

Anthony
Anthony

Dave O'N/Rich

I can't see how joining all the breathers together into the carb would help. The flow will still be restricted by the single pipe going into the carb, no matter how many others are joined onto it.

I think Dave B's idea is best to have a couple of 1" breathers somewhere. I'll be putting at least one in the sump, another thru the fuel pump blank and I also have a smaller one out of the rocker cover.

Then again, not having pistons which waggle from either side in an alarming manner might help.
Tarquin

... actually the flow is restricted by the vacuum pull through the carb and the restriction of the breather cap on the rocker cover. If you remove this cap, or provide other breathers, then the vacuum in the crancase will disappear.

A
Anthony

Tarq, I have those breathers, but where will you route these 1" breathers to?
Rich Amos (1330cc Blaze Red '72)

Anthony

no-one listening!

there should be no need for extra oil breathers.

if there is there must be something wrong on the "extract" side of the system and no number of extra gizmos is going to cure it.

The famous P.M. oil seal kit advises that for it to work you need to clean out all the accumulated crud of ages gone from the chain case canister by soaking for a goodly while in thinners to soften hardened crud then swill it out. you still need the gauze inside though to catch heavy fume solids

(it doesnt mention repainting the chain case, believe me, you'll need to) then ensure a good clear pipe to the inlet manifold connection so the manifold vent can draw it through

then expect to see the garage floor puddle reduce to a signature "spot"

even with the kit and after two or three years (I forget how many) there is an occasional spot somewhere, but I think it may well be the type9 "relaxing" after use.

If you have breathers you will lose the "less than an atmosphere" effect inside

oil will flow sure as eggs is oval
Bill

Buy two PCV's en connect them to the inlet manifold and the various breathing points
arnold

Bill,

<<oil will flow sure as eggs is oval>>

Not heard that one before, sort of depends which way you look at the egg though.
David Billington

Think of the Vacume system like this....


Pos. pressure-

A pump up garden spayer...put fluid in the sprayer and pump up the spayer(your pistons) you got pos. pressure...put a hole in the sprayer below the fluid line(your leak) and the fluid will shot out.

Neg. pressure-

Use the same garden sprayer with fluid in it, and tap the sprayer ABOVE the fluid line and attach a Mity vac. (the little vac. pump with a gauge to suck air out...like on a d*ck pump) suck the air out and you have Neg. pressure....Meaning the fluid will NOT leak out the hole below the fluid line(your leak)

put another hole above the fluid line (aka breathers) you lose the neg. pressure, making a 1:1 atmospher pressure ( the pressure is equal ) and the fluid WILL drip out the hole below your fluid line(your leak)

Combineing POS. And NEG. Pressure-

If you have a motor running the pumper on the sprayer,,,your creating the pos. pressure (your pistons) and you have a hole below the fluid line (your leak)you will shot fluid all over the place...If you can pump the (the d*ick vacume pump)hard or fast enough to to suck MORE air out of the sprayer then the motorized pos. pump can Put air into the sprayer...then the fluid WILL NOT flow out of the hole below the fluid line (Your leak is fixed)...if you put a hole in the sprayer (breathers) above the fluid line, you will lose your neg. pressure and the pos. pressure will over power or equalise the neg. pressure and the fluid will escape thur the hole below the fluid line (your leak)

Im using "Air" instead of "pressure" for better conceptalization....but you get the idea.

god Im great!!!
prop
Prop

Rich,

I agree with Bill. We have a 1380 with an HIF6 SU. Breather tube connected from the timing cover to the SU, plus oil filler cap with breather/filter and only a very small oil weep from the rear main - standard scroll.

This worked with the standard timing cover and now with a vented cover on a timing belt conversion.

I would suggest reverting to the standard breather solution and go from there. Some vacuum is essential, which will be lost if you add any additional breathers at all.

You do need the vented oil filler cap for it all to work. The system draws air in through this, but evacuates through the carb at a higher rate, thus causing a partial vacuum that keeps the oil (or most of it) inside the crankcase.

Richard
Richard Wale

To add another penneth...

1330 with a 45 Weber catch tank vented from timing cover, block and rocker cover into a catch tank vented to atmosphere. No oil from the rear scroll.
Daniel Thirteen-Twelve

Daniel,

Thanks I was feeling lonely as one without oil leakage and no vacuum drawn on the crankcase and a standard rear scroll seal. I think the 1275 crank and 1098 crank have the same sealing arrangement, IIRC an oil slinger disc then the scroll before the flywheel boss, as I have a 1098 crank in the 1420.
David Billington

Just another..

I ran with a single K&N breather filter last year and had a large oil leak (and lots of fumes getting inside). Reverted to the breather into the carb and the leak was much reduced.

If I did go for lots of breather I'd make sure they all went to a catch tank under vacuum rather than atmosphere.
Dean Smith ('73 RWA)

On my set up, my engine is standard apart from the hif44 carb, modified head and high lift rockers, are we saying that my 12mm ID bore breathers are too small? (I know the step down to 8mm to fit the carb body probabley is) If so how do I get an 1" ID pipe to stay on the tiny vent port on the carb body?
I must say I feel like we are getting somewhere with all your comments..Im definately going to use just one breather from the timing case to my carb, block the mech fuel boss vent, and use the vented oil filler cap. Fingers crossed I will get the odd drop of oil I used to get with my twin su set up, rather than the dripping tap effect I get now!
Thanks all, keep them coming.
i coxon

Ian you will just have to "step-down"

I do with my HIF and have, as I say very little drip-by

I have 1.2" pipe off the canister and feed that onto a smaller diameter hose that fits the HIF suction vent tube doodah

I sealed the joint between both with self amalgamating tape, job done

You can sort of see it in this very blurry picture


Bill

So I'm decided from all this that my best bet is to try blanking. So...stupid question... how do I blank these 2 breather pipes on the sump and on the rocker temporarily? Is there some sort of 'bung' I can get?

We'll see how that goes...

Rich Amos (1330cc Blaze Red '72)

how about taking the pipe along from one and popping it on the other?

balance?
Bill

Bill, Thats just what I had in mind, and to be honest its what im doing now, only with smaller bore hose, plus my step down piece is a touch too long (about 6 inches) thinking about it now, im not sure why!
Any case, I will get hols of some pipe and give it a go. I have some nice blue silicone hose, but its 12mm ish ID , I take it this is still too small? Is 1" the way to go?

i coxon

I'm not a scientist, so I dont see how much it would matter

I'm damned sure I'd try with whatever was to hand before spending unnecessarily

12mm isnt that far off the 15mm usually quoted as 1/2" is it?

:+)
Bill

Ian,
My engine is similar to yours, but without the high lift rockers. I changed from twin SU to single HIF44 last year and the oil loss increased, but only very slightly from almost none at all. Occasionally it now leaves a drip or two overnight, that is all.
I use only a single breather pipe from the can on the timing cover to the port on the HIF

Easiest way to close off the unwanted breather ports if you don't want an extra hose wandering between the two is to use a short (1") length of hose with a stubby bolt pushed in the end and secured with Jubilee clips.

I have even seen it done using old spark plugs! ;-)

Guy
Guy Weller

Bill, I guess not, I will try my 12mm pipe, which is much bigger than that im currently using. So are you using 1/2 " ID pipe? Think I misread it for 1.2" (one point 2 inch)

Guy, thats exactly whatseems to have happened to me when I swopped from twin su To single hif. I had virtually no leak, to quite a noticeable leak. So im hoping the single breather from the timing case will help.

Thanks all, will keep you posted one the weather eases, and I have spare time to take her out.
i coxon

Oh bugger...

true confessions time again

I havent measured mine

I just found some hose that fitted the front canister outlet and fed that into the size that fitted the carb breather vent inlet
taped round the outside with the self amalgamater

couple of jubbly clips

and

job done and working
Bill

He he nevermind Bill. I have fitted a 12mm hose from the front canister and fitted a smaller bore pipe inside this one at the carb end, fits like a glove. Only problem is I didnt have a length of hose long enough , so for tempory measure to see if this works, I joined two lengths of 12mm using a piece of copper pipe as a straight coupler in the middle.
Just need to take her for a spin, fingers crossed, and hope it works.
Will keep you posted
i coxon

I'll keep 'em crossed for you

should be fine
Bill

Thanks Bill, Still Havent took the car out yet, ...just not enough hours on a sunday!! Will do soon, and post the results.
i coxon

Same here, still haven't done anything, too busy fixing bikes (and keeping my fingers this time!) but soon, soon!
Rich Amos (1330cc Blaze Red '72)

Rich,

Firstly I admit to not having read the whole text, however we always deal with vent issues at FMC-Powertrain and here would be my thoughts based on that experince.

If you have some breathers vented to atmosphere and another to the carb. The carb will be drawing air back down the two breathers open to atmosphere into the engine. This increased rate of gas will give a high vent gas speed and will not allow the oil time to separate out of suspension in the air.

The separator on an A-series drawes air from the centre of the cam sprocket. The spinning sprocket provides an means of cetripetal (spelling!) separation before the gases go into the separator tube. The wide diameter of the tube allows the gas to slow, and provides time for the oil to fall out of suspension and drain back down the large tube into the engine. Thus I would suggest this is the most effective point to draw the vent gas out of the engine.

If this still does not provide adequate degasing, then use multiple breathers, but put them all into a catch tank, not say two into a catch tank and another into the carb, due to the reverse flow situation.

If you wanted to break new ground I would suggest perhaps making your own separator. I would use a large tube like device similar but larger than the original. I would introudce the vent flow at a tangent to the bottom of the tube, to promote a swirling flow in the tube. This cyclonic action will aid the separation. The gases should then be permitted to exit the top and center of the tube. The bottom of the device will need to be able to drain the separated oil back into the engine, to prevent vent gas being draw through the drain, return the pipe to the oil pan below bulk oil level.

My 2P worth. JE
James

JAMES JE

Very interesting and no mention of blocking up breathers which always seems like a bad idea.

For any engine with breather pipes feeding into a catch tank clearly the flow of gas should aways be breathing out of the engine into the catch tank.

However, the argument exists that it's beneficial to have a partial vacuum in the sump and that venting the engine to a catch tank can't do this.... unless ..... non return valves are fitted to the breather hoses? What do you think?

Daniel Thirteen-Twelve

I still havent took the car out for a drive yet, but soon as i have my weekends back once i start my new job, i will be out there. Any way... I took my other car (punto) for its MOT on monday and spoke to my mechanic who has works on many a-series engined cars, I mentioned the leak I have , and indeed he has seen it when she was MOT'd back in may. He suggests to remove the wire mesh from the separator. They always did this even on standard cars. The reason he gave was, that even though when blowing through the pipe it seems free flowing, and the mesh may look clean when viewed through the top of the canister,in his experience they generally sludge up at the bottom. So when the engine runs the oil cant return back into the sump properly, and can cause a pressure build up causing the leaks.
Just another idea to throw into the pot.
I know Im going to try and remove mine, (without removing the timing case if poss, as my crank nut is a real bugger to get undone!)so Im absolutely sure its clear. If IRC Tim at frontline recomends this on newly built engines, and im sure someone else mentioned it too, Bill i think.
i coxon

Prop,
i use an evacusump system as described in Vizzards book. It requires about 1200rpm to develop enough vacuum before the engines leak free.
You can up your idle, live with the drips or change your cam :-)

Brad
B Richards

Rich - http://tinyurl.com/3lmjpb
Toby Anscombe

Too small a tank for speed events or racing unless purchased in multiples!
Daniel Thirteen-Twelve

Just looked at Morosso's site, looks like the original exhaust evacusump is no longer available, however this Vac pump is

http://www.moroso.com/catalog/categorydisplay.asp?catcode=17200

Brad
B Richards

Brad

Any chance of a photo of yours in place?

Carl
C Bintcliffe

I've fitted a 'loop back' which just connects the sump breather to the rocker breather directly. So far I'm still seeing some leakage from the car, though it is of course, driving just as well as before.

the leak is definitely coming from the rear of the engine. There is very little oil till you look underneath and see that the clutch slave is covered in oil, as well as the pushrod, along with the earth strap, which subsequently channels oil down the chassis rail!

I think it's going to need an engine out and rear seal replace....
Rich Amos (1 Sprite 1 Midget!)

Heres an old photo of the tee in to the exhaust just past the LCB.


B Richards

And another old photo showing the Morosso one way valve, it's at the NS front.
From the valve the hose goes directly to the timing cover.
I now use a another tee with a modified one way valve to a small K&N. As the evacusump needs about 1200rpm to work, below that you get no vac, so i vent to atmosphere via the K&N, when the evacusump is in operation it closes the one way valve to the K&N. Bit of a set-up but it seems to work.

Before i get a heap of emails, i have changed the rocker cap type as well.

Cheers
Brad
B Richards

Doh,
forgot to attach the photo!


B Richards

Rich, I know exactly what you are experiencing. Although I still havent taken the car out for a test run with amended breathers, the oil leak and pattern of it creeping back and covering the clutch slave is just what happens to me, and did before even when my leak was minimal. I just hope I can get the leak to a minimum this time, as I dont really want to pull the engine again, asI know my real seal is less than a year old.

Good luck and fingers crossed.
i coxon

This thread was discussed between 28/09/2008 and 23/10/2008

MG Midget and Sprite Technical index

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