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MG Midget and Sprite Technical - Catch tank/ Oil separator question

Interested in getting a catch tank / oil separator for the frogeye, it has a slightly hot 1330 (single Hif44,) with a 276 Kent cam. Any good suggestions that aren't either very expensive or a couple of pipes in a jam jar.
G Lazarus

plenty on ebay
the china ones are good value but take 2-3 weeks to arrive
There are some nice kits on there with an hose fittings and hoses supplied
You need to work out if you're having an oil return or manual drain and if you want a breather on it
If you use your car for competition, i don't know your regs. there but here there are minimum capacity sizes depending on the size of the engine

personally, I think for a tank to work properly you need the engine breathers sealed off and the breather hose or filter(optional) on the tank only, with a return from the bottom of the tank into the oil pan below the oil level

Found this universal one that has plenty of threaded holes and fittings for hoses / filter etc
William Revit

I have one that you can have.
Alan Anstead

Ooh thanks Alan.
G Lazarus

If it turns out Alan's isn't available he-who-can't-be-mentioned has said -

Hi Nigel,

Thread: Catch tank/ Oil separator question

Point Gary to one of these.

Iíve put one on my Consul Capri 1500GT. Works REALLY well.

VERY cheap purchase, BUT NOT cheaply made. In fact itís VERY well made.

Mine is part of the PCV system, that I modified to make it fully sealed.

(name redacted)

see below

Nigel Atkins

My engine spec is about the same as yours. My catch tank is fed from the timing cover and rocker box and open to atmosphere via the cap. Never seems to collect anything.

f pollock

Nigel. Please pass on my regards to he who can't be mentioned.😉
b higginson

If they're not already seen I will do.

Do you want me to include it as a part of a rehabilitation program. :)
Nigel Atkins

Best wishes to "Him" from me too.
G Lazarus

Will do Gary.
Nigel Atkins

Bernie, Gary, regards are returned.
Nigel Atkins

Nigel ditto from me OK?
Bill sdgpM

Bill, done.

How are you and the car?
Nigel Atkins

Bill your greeting have been returned.
Nigel Atkins

While You're on a roll Nigel could you pass on a hello to L from me please-not urgent -----next time you're in contact's fine -
William Revit

Nigel doesn't really need to 'pass on' these comments as Mr S keeps a fairly close oversight of many of the topics anyway. A mention of front wheel bearings,lower wishbone bushes or oil burning and he will be there watching over the discussion and probably grinding his teeth with frustration when we get it wrong!

I guess that's right but he missed all but the early posts so isn't always an avid reader.

So Willy I will pass on your "hello".

Nigel Atkins

he who can not be named says "Hi Willy".
Nigel Atkins

Cheers Nigel
William Revit

There is no such thing as a silly question, although, I asked about a smoking exhaust, which must have been a silly question because I didnít get a single reply. I thought I must be the only person in the world with this problem. I had already looked in the archives for a solution with no success. I didnít know I should have been looking for breather or sucking oil, but then if I had known that was the problem I wouldnít have needed to look anyway. The problem had been discussed at length, but I wouldnít know that since I was new to the forum. I still wonder why nobody pointed this out. I thought just gas was drawn from the sump, it had for 28 years. Having had those Ford windscreen wipers that worked on the depression in the manifold and been told by a mechanic the depression was negligible and by another that this is the reason for turbochargers, it hadnít occurred to me it was possible to suck oil out of the sump. Someone gave a link to a SU tutorial; it then occurred to me that the dashpot oil could be seeping into the cylinder and causing smoke and misfires. When I pointed this out I was ridiculed by the unmentionable chap, his p*** taking did lead me to a solution. Nobody is obliged to help I know, but this is what the forum is supposed to be for and would have saved me a load of aggravation.
L Langley

It's odd that you got not a single reply to your question. If you look at the listings of discussion threads very rarely indeed are they limited to a single post. Usually someone asking advice or help gets lots of response.

The fact that your question may have been asked before doesn't usually stop those prepared to help. Most people here are friendly and very willing to help, especially with newcomers. I think your experience is pretty unusual. But finding answers by searching the archives can be very hit and miss, and can take a long time even when you have a fairly clear idea of what you are looking for!

Hi L Langley,
a thread can be missed for a few reasons I'd guess but not usually because no one wants to help or reply. Sometimes attention is drawn away by activity and interest in another thread or threads distracting from a new thread started. Also you may not be aware that there can be different settings to how the BBS, threads and posts are seen and the way you have it set up may be different to others so they're not exactly seeing the same presentation as you.

Often if I see a thread started without a reply I will put a reply, even if I know less than I usual don't know, just to highlight the thread and perhaps get further more useful replies. I don't think I was around for your thread, or at least I don't remember such a thread, or perhaps I too didn't see your thread without a reply. I do sometimes hold back for a more knowledgeable poster to reply but can always be relied on to at least give an opinion, as my mate says "everyone is entitled to Nigel's opinion".

So was it dashpot oil that caused the smoke, and what oil were you using, not everyone uses engine oil, I'm sure you'd get plenty of replies and opinions on that. :)

I'm only half joking with this, not in your case with no replies, but many posters now seem to post asking for information get lots of varying information and the poster never returns to the thread with the solution or result meaning others can't fully learn from the thread as it's literally inconclusive.
Nigel Atkins

just had a look in the archives and I can't find it L.L
Can you remember the exact thread name--?
William Revit

Thanks for the replies, I think I owe you chaps an apology, it is clear now that had you seen my post you would have responded. The post was definitely at the top of my list for three days, although I canít find it in the archives under Smoking exhaust or Clouds of smoke. Maybe being the first post after signing up it didnít go through, I had no trouble with further posts.
L Langley

perhaps you posted on another section of the site by mistake - I've hit one of the MGB sections before when I didn't mean to.

I don't know the terms but the computer or search wotsit can hold an old image (my wrong word) of a site or page if you loose live connection to the site, or sumfink or sumat like that. Otherwise I don't know what or how you get an unanswered thread to remain at the top of a list.

I found a thread started by you 18 December 2015 in the midget and Sprite General Archive, titled Exhaust smoke but it has replies. One was from he-who-can-not-be-named but I didn't notice any piss-taking in it, certainly not to the usual standard. Perhaps this thread was after your initial thread and not the one you refer to as it was you that was a harsh to our shrinking violet former poster.

All water (or urine) under the bridge now. :)

Nigel Atkins

Ah yes, it was in the general section
Just reading it, yes ,I can see that if it was your first posting that it could be taken as a not interested - said member's dismissal of your question may have been a touch short in nature, but looking through his eyes it was probably a case of 'here we go again' and really his reply was quite tame
As Nigel suggests , water under the bridge is the best approach

Main thing is that you are still here now
The more the merrier as far as I'm concerned
The bigger the variety of members the better the content gets--Hang in here LL everyone's welcome

I see the Technical section as the place to ask questions like yours and discuss problems and methods used to repair or replace things
To me the General section is more of a place to go for general Midget and car(sometimes)based chit chat and can be a very interesting site at times
William Revit

With many thanks for the donation from Alan Anstead. I owe you beers

G Lazarus

Here is another idea. This one is smaller, and can just be mounted inline so it doesn't need to be mounted to the bodywork. You can see I simply plumbed it between front can and carbs. Not for competition, but I have it just for additional cleaning of oil before being sucked back into the engine. I recently checked it after a 2600 mi. trip and it had collected 2 tablespoons of oil. Don't know if that is significant, but its 2 tbs. that didn't get burnt in the engine. Cost is more than the others shown, and shipping may be high, too, but just an idea. See more at Item no. 555-52206

Jack Orkin

This is connected with this thread, I was going to write about my catch tank saga, but I have another problem. Returning from a show a week last Sunday I parked on the drive for a couple of hours, after pushing the Sprite into the garage there was a large pool of oil on the drive. The next day there was another in the garage. It seems the oil is building up in the timing cover and running out of the crank oil seal. Poking a wire down the hole behind the crank timing sprocket it is clear till it hits a solid wall. Does the gallery turn down at 90 degrees? I have tried blowing it with a compressed air canister, but I think it is still blocked. Going to borrow a compressor tomorrow, or has anyone a better Idea? - Many thanks.
L Langley

LL: oil smoke in the exhaust has been the subject of EXTENSIVELY long posts here, equal to front wheel bearings. The issue is simply that certain engines can draw oil up from the timing cover into the manifold if the two are connected.
"He who shall be nameless" produced extensive test reports. The whole issue is rather like "ghosts" -either you believe or you poo-poo it. Believe me two of my three 1275 engines have suffered this!
Graeme Williams

Indeed yes.
But what is interesting about this observation is that the lack of oil drain is caught on the act.
Do either to much oil is getting in there or the
Exit is restricted. Nothing that a major strip-down won't solvr
Paul Walbran

Thanks for the reply Graeme, yes too numerous to read and there is not much in there on cause or cure. My namesake did a lot of work on the subject, he is a great loss to the forum. My latest problem was oil pouring out of the crank seal in the timing cover, obviously the oil wasnít returning to the sump. This is the root of the problem, too much oil being pumped in or not enough getting out. What is remarkable is that this problem seems to be unknown outside this forum. Saying that, overhearing a bloke, at that show, talking about a 1952 Ford Consul he had with vacuum operated windscreen wipers. It had a booster vacuum pump driven from the camshaft. This could pump oil into the manifold causing smoke and misfires. He cured the problem by blocking the manifold pipe and putting on electric wipers. Before that he had taken the head off and I believe was about to take the pistons out till a mechanic told him what the problem was.
I can sympathise, I didnít connect the missing with the clouds of smoke or with the engine sucking oil. I had a bloke with a Sun tuner and forty years experience working with carburettors, check the motor, he did examine the valve but found nothing wrong. I took him on a ten mile trip; apart from one blip it ran perfectly. I donít think he was aware of this problem. The following day I did fifty miles with just one blip, but the next day it was misfiring that badly I struggled to get home after two miles. Then I found out what the problem was.
I soldered, into the top of a syrup can, a 15mm copper pipe and one on the opposite side more than 50mm apart, it didnít work. Then a 22mm copper pipe stuffed with gauze and reduced to 15mm each end and connected directly to the sump above the oil level; that didnít work either. Then I used a flour can 200mm deep with the in pipe going into the can 175mm and the out pipe close to the top. This was successful, the motor had never run so well. I was thinking about making another with a drain plug when that one on e-bay came up. That is really good for the money, but I was dubious about the hose connections being adjacent to each other. I pushed a 10mm central heating pipe into in hose connector to keep then 75mm apart. It works but the motor doesnít run so well and pops in the exhaust with the foot off the accelerator. This is connected to the sump so the flooding of the timing cover is a separate problem.
On a forum a poster had this problem, he found the drain hole blocked with a leaf of gasket cement. I didnít find anything blocking the hole, perhaps I had been over zealous with the cement last time I took the cover off and a piece was in the gallery. It was pointed out that this occurs after a recondition, it did for me. Perhaps it is as simple as gasket cement blocking the drain hole. I had thought about a new oil pump being more efficient, but it would have occurred with new vehicles. Got to put it back together now
L Langley

Paul I was typing while you were posting. I agree I don't believe in magic either. I had posted a picture of the flour can but it hasn't appeared.
L Langley

Yes, gasket too would be my pick, there aren't that many other variables. Drain holes getting hardened arteries could be another. Happens gradually as an engine ages, but oil pump output bleeds off in many dire tons for the same reason. Then put a new pump and reduced bearing clearances, and maybe there is extra flow into the timing cover.
Maybe a thing to do during recon is to open the drain holes a little.
So see how many auto-not-correcys I scored this time...
Paul Walbran

I found cold oil made the problem worse due to higher viscosity and it only occured when the oil level was near Max. My current engine does it very briefly after about a mile where there is a roundabout or traffic lights. The oil separator tank solves that and collects about 5 mll of oil each run.
Graeme Williams

Paul: I know at the time "the nameless one" carried out some very extensive tests with several engines, with timing covers with transparent panels and so on. No obvious blockages. At one point over delivery due to worn or dished cam bearing and plate was suspected.
It just suggests that the difference between flow out of the cover compared with flow in can be marginal and small changes (cold oil for example) can upset the balance and cause the level to rise until it floods the breather. The "what" isn't rocket science but the "why" seems to be.
Graeme Williams

Oil surge in the sump under heavy braking (for Graeme's roundabout) is also a factor, probably reducing the rate of return of oil from the chaincase.

Catch tank photo:


Just a belated update. I fitted the catch tank which resulted in losing vacuum in the engine, leading to a drip drip drip oil leak ( about two drips per second) from the rear of the engine. Quite surprising as I have a Datsun 5 speed with a rear oil seal. I replaced the hose from the timing chain cover back into the carb and the dripping stopped immediately. I may try reconnecting it back with the catch tank inline with and without the catch tank breather between the timing chain cover and the carb, to see what that does. I'll keep you informed.
G Lazarus

Guy - Thanks for posting the picture of your Illy tank system. I couldn't remember who had posted about it previously but it did prompt me to copy it (I hope it's not patented!) to try to lower the crank case pressure and reduce rear oil seal drippage.

I found that only Illy seem to supply foodstuffs in screw-topped containers with metal lids.

The components used were two screwed pipe fittings, a 'table' made out of expanded mesh to create a void at the bottom and two stainless pan scrubbers sitting on the table, a length of thick walled hose.

One pipe fitting is central in the lid, with a length of hose going down through the scrubbers to the void. The other fitting is off-centre, drawing fumes from above the scrubbers and feeding into a hose running to the PCV. I knocked up a nifty connector between the timing cover canister and the Illy can with 15mm copper pipe and a couple of elbows, connected at each end by short bits of hose.

The Illy can lid is not air-tight so I seal it with electrical tape.

The drippage definitely reduced and, for the best part of two years, there was only a few drops of water condensate and a coating of oil in the tank.

Last winter I tried the Sprite without the tank and it started to smoke on accelerating away after ticking over at junctions.

The system is now back in place but collecting quite a bit of oil. As I've done absolutely nothing else to the engine, I can only think that the piston rings have given up. I keep meaning to do a compression test but I suspect the engine's going to have to come out over the winter.

C Mee

Gary, is your catch tank connected to the carb on its outlet side? It should be, and assuming the tank and plumbing is sealed sir tight, then the suction will be the same as before.

Colin, yes your system is pretty well exactly as mine, including the need to seal the illy lid with tape! The connectors on mine are made from DIN cable connectors with the internals removed as they were neater than plumbing fittings, but inside the tin the use of SS pan scrubbers and one shirt, one long pipe is the same. It does seem to work well enough for my 1275 set up.

My recollection of the Illy tins was that they had a seal as I used to drink the stuff. Maybe they have changed, IIRC a seal of some sort should be there to help keep it fresh.
David Billington

Yes they do have s plastic liner inside the lid, which does form a seal of sorts. But not really good enough so a turn of tape (duck tape, in my version) completes the seal. The tin fills so slowly with condensed oil vapour that it only needs disturbing to wipe clean inside every 24 months of so, by which time the tin itself is beginning to deteriorate. I have just renewed the tin in mine

It occurred to me that if the oil is entering the timing cover from the camshaft and returning to the sump by gravity the gas from the sump is going in the opposite direction through the same gallery, there is a problem here. I thought taking a pipe from the sump would prevent any build up of oil, but not so. After less than 100 miles there was 180ml of oil in the flour can. The oil in the timing cover should have been sucked into the sump, it wasnít.
L Langley

LL, there is,or should be a much larger opening between the chain case and the main crankcase above the front crank bearing that allows the crank and chain case gas pressures to equalise.

I say should be because it is formed by a rough "knock out" in the block casting aligning with a machined circular hole in the front engine plate. Conceivably this might not be cleared during manufacture, but I think it extremely unlikely.

Oil is pumped into the chain case via the gallery that also feeds the rocker shaft and cam shaft (gallery splits just before front cam bearing). Changes to the oil pressure at the front cam bearing can be caused by a decrease or increase of flow elsewhere in the pressurised part of the oil circulation system so if it's arriving in the chain case faster than it can drain away you may need to consider what else may have changed in the whole system.

Is this any good for you Gary, its our combination tank, can be water header and washer bottle or header and catch tank.


Guy, wish I had read your post before I put the sprockets back on (yesterday) and the timing cover (today). Can't recall seeing any other hole than the one below the crank. If this isn't solved this time I am going to SORN the motor. I am getting too old for this; my grandsons can sort it when they are old enough, if they are interested.

L Langley

I totally understand your frustration, I've had it a few times with my classic cars particularly when I or others have done work on my cars.

SORNing the car would be one of the worst outcomes - but things are not as dark as they seem.

There is a cause and cure in that thread you refer to - "the cause is too much oil entering the timing chain cover, exactly why that happens, and why only to some engines, is what was not entirely established".

The last post -
"Just letting you know that I still haven't sucked any oil at all, since doing the modification. But more than that, the engine goes so much better with the modification. I've even turned the mixture screws up. There must have been an amount of oil always being drawn up, even after the 'big' smoke ceased.

I might even go so far as to say it's worth doing even if you don't get the obvious oil sucking. Especially to an engine that already has a drilling for the mechanical petrol pump, since it's such an easy mod to make".

Lawrence has sent me photos of "additional oil separators, that COMPLETELY stop oil sucking, and obviate the need for a catch can at all, whilst still retaining a fully working PCV system".

If you want I can send you the photos and/or give you Lawrence's email address to get the full info straight from the horses mouth. Lawrence was extremely helpful and knowledge when I had my FWBs problem and has helped with other matters, always lively views but also always helpful.

My address is above.

Nigel Atkins

"and obviate the need for a catch can at all, whilst still retaining a fully working PCV system".

Just to clarify as this it might be interpreted that a Pressure Controlled Crankcase system and a catch tank are not compatible. (I don't think Lawrence meant it like that). They work well together. A catch tank like mine is sealed and in line with the PCV so it actively lowers Crankcase pressure and extracts and catches and condenses oil vapour.

At one time I had a pcv connected between the breather and the manifold (no catch tank) - there was no carb connection on mine. When I started up after about 10 seconds I couldnt see for exaust smoke and when I rushed round to turn off the ignition, the car kept running for about 15 seconds dieselling on the oil. On that car I subsequently left the breather open and accepted the oil drip at the rear. I sold the car like that.

Of my two current 1275 one has a catch tank and connection to carb (small volume of oil). The other currently has nothing (and no leaks either)

It seems to be the general observation that the same engines do not spew out oil if the breather is left open to atmosphere - it's only the suction that draws it up.

How about a chat about Front Wheel Bearings...... No-one?
Graeme Williams

A small consideration but one of my set-pieces - the bling metal oil filler caps only have a very small hole in them whereas the original type black plastic oil filler cap has a much greater area of opening(s) (and a mesh filter).

Nigel Atkins

Mine ran splendidly open to the atmosphere, but left a trail of oil around the neighbourhood.
L Langley

This thread was discussed between 20/05/2019 and 19/07/2019

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