Oil misting

[Jimgreen01]

Hi all,

I know there are loads of posts about this in various forums but I’m getting a lot of oil misting, it’s pooling in the valve cover pipe”lip” and the underside of the hood. 
I have a 4 that was first registered in the US in 1964 but looks to have been made in 1963.

i am not convinced that the draft/venting set up I have is at all standard - see attached pic. 

My question is - would a vented oil filler cap help or not?

I don’t particularly want to retrofit a PCV from a later model. If a catch can could help them maybe a yes to that. 

Any advice or reducing the misting? 

Thanks!

[Trumpy3]

Jim

I suspect your car would have had a PCV valve that has been removed. In this case there would not be a crank case vent fitted. This is a pipe fitted down behind and under the fuel pump. Cars with a PCV do not need this vent as the crank case needs to be sealed to work. This would mean the engine's only breather is the single pipe from the rocker cover and this is not enough. Your rear and front crank shaft seals are probably leaking a bit also due to a positive pressure in the crank case.

A vented cap would probably not provide suffiecent breathing to prevent your "misting issue". I do not remember if the TR4s with PVC had the boss cast into the block for the vent so not sure how you can fix it.

Brian

 

 

[Bfg]

Hi Jim,

The rocker cover / crankcase breather setup your car has is familiar from original photographs I've seen. I suspect it's of US spec TR4A's with Stromberg carburettors.  I thought the TR4's had the crankcase breather 'snorkel' alongside the fuel pump and no vent in the rocker cover, but of course that may have just been UK spec cars, and later TR4's of California emissions may have swapped to your car's configuration sooner than our own.   I'd suggest the design of breather is correct, using the draw through the filters to evacuate air pressure from the crankcase, but the component parts and the pipe clips may not be,   

My own car is a TR4A with SU carburettors, which I often drive hard. It has a rubber pipe from the rocker cover (in the same position as yours) but the pipe is led down to ground, outside the chassis.  The engine is good condition now and mostly only condensation comes out of the bottom of the breather pipe. 

In any case the breather pipe should be a tight fit, whereby no mist escapes over the top of the engine.  More likely your oil filler cap is vented, whereas it should Not be.

Alternatively the oil filler cap's seal is leaking ..whereby oil splash from the rocker arm is then a weep out from under the cap.   Again it's unlikely to form a mist over your rocker cover, but it would be enough to leave a puddle in the rocker cover's rim.

The usual place for oil to leak is ; from the rocker cover's stud holes.  I've sealed mine with 2mm fabric-reinforced rubber and then stainless steel penny washers under the nuts (please see attached photo).  You'll note that there's a cut away segment of the rubber washers - just locally to clear the raised rib of the rocker cover (..so the rubber sits flat to the cover ).   Even if these weep, it's unlikely that they would cause a mist of oil.  

Excess breather pressure is caused by blow-past of combustion cylinder gasses.  This is easily identified by checking the cylinder compressions.   Using carburettor cleaner as a spirit solvent, and clean paper towels to dry everything thoroughly - with a clean engine you can start afresh in tracing where an oil seep originates.   

Oil mist all around the engine and on the underside of the bonnet may be from a leaky front crankshaft seal.  Oil leaking from there spins out from the fan belt pulley and is flung into the fast flowing air from the cooling fan. This is of course thrown back over the engine and under the bonnet.  Again, cleaning and systematic running the engine and examination will help pin-point the cause.  From your photograph it doesn't look to be the issue here. 

It looks from the photo as if you have a weepy oil filler cap, and likewise from the rocker cover studs each contributing to the oil in the rim.  Rectify these and then see if you still have an issue.

Hope this helps,

Good luck, P..

Edited November 7 by Bfg

[john.r.davies]

I agree with BFG - if the oil is pooling on the lip of the rocker cover, then it's coming from the filler cap, or around the hold-down studs.    He shows those with large washers with a rubber seal under them.  Here's another way, that is less obtrusive.

Fit washers that are a loose fit on the stud, but only just wider than the nuts.    Before you add the nut, put on an O-ring  that is a snug fit on the stud.   The nut will compress the ring into the annulus between stud and the hole in the cover, without it going  through.    It's very effective!   And all that can be seen is a small washer under the nut.     The O-rings need to be replaced every time you lift the cover.

John

[stuart]

On a 63 TR4 before CT25394 it should have the engine block snorkel down on the L/hand side below the fuel pump After that it has what you have for rocker cover breather and the snorkel was replaced with a core plug. How much pressure is there if you remove the rocker filler cap when the engine is running?

Stuart.

[Z320]

Hi,

the knurrled nuts on Jim's photo are ideal to cut a notch for an o-ring!

This is what I did:

I measured the total length of the studs, the length above the cover and caculated the length above the cover.

Cut a tight on the studs fitting petrol hose some millimeters longer, the propper cut as well as possible 90° angular,

and slide them over the studs to be compressed by the cover - sealed!

Ciao, Marco

[Jimgreen01]

Guys - thanks for all your input (although I did have to look up what annulus meant 🤔).

I'm going to try a new filler cap (the current one is not vented by the way) and new fittings around the hold-down studs first and see if that helps.

The car is US spec - CT25510-L.

@stuart - can you let me know how i would test this? Just from "feel"?

Edited November 7 by Jimgreen01

[trchris]

Remove the dipstick engine running and see how much pressure is coming through the tube using your thumb 

Chris

[Jimgreen01]

Will do. Thanks. 

[stuart]

Or remove the filler cap from the rocker cover while its running and put the palm of your hand over it and see what pressure you have there as well.

Stuart.

[BlueTR3A-5EKT]

1 hour ago, stuart said:

Or remove the filler cap from the rocker cover while its running and put the palm of your hand over it and see what pressure you have there as well.

Stuart.

I would have guessed none as the rocker cover is vented via a hose and Y pice into the atmospheric side of the air filters.  
 

The oil puddle on my rocker cover outer lip was primarily from the standard venting push on oil cap but also drips from the attachments nuts.   Solved with seals as Marco describes and added a turned mushroom inside the oil cap to catch oil splatter, rather that it getting up in the cap and dripping through the wire gauze filter.   
After a motorway thrash the rocker cover exterior would be well oiled.  Now it is completely dry.

my car is with standard block side snorkel vent and breathing type oil filler cap.

 

Edited November 8 by BlueTR3A-5EKT

[Jimgreen01]

Well I tested the pressure this morning. With the filler cap off, I could feel what seemed to me to be good pressure, although I have no way of really knowing good from bad!

The dipstick "hole" was less so but definitely some pressure there also.

Now just waiting for some parts to try replacing cap and hold downs.

[john.r.davies]

Crankcase pressure comes from piston blowby, and apart from poor extraction, excess pressure comes from poor ringbsealing.   Havevyou done your bore compression pressures?

John

[Jimgreen01]

No - not yet - going to try the sealing methods first.

[john.r.davies]

52 minutes ago, Jimgreen01 said:

No - not yet - going to try the sealing methods first.

Hmmmmmmmmmmmmm!  That's a bit hopeful.  If you do have excess pressure. it's going to leak out somewhere!

John

[Jimgreen01]

Yes. We live in hope and we die in despair apparently. 
However it’s not a sealed unit. There is the venting mechanism shown in my first post. 
If the seal improvements suggested above don’t work then I’ll get the compression tested. 

[john.r.davies]

A tester is cheap, and while detail essential, the method is simple.  

Warm up engibe, remove all plugs, fix throttle wide open, disconnect LT wire from coil.

Screw in tester, turn engine on starter unti guage maxes (4-5 turns)

Read guage.

Repeat on next cylinder.

Repeat whole test, until individual bore readibgs are consistent.

Good luck!

John

 

[Jimgreen01]

Thanks John - I will certainly do that.

As an aside, having cleaned up the valve cover, cleaned out the venting tubes, replaced the filler cap and fitted the o-ring suggestion above, I am getting a leak still and its now very obvious its coming from under the hold down nuts.

[john.r.davies]

You have a source then!  See earlier posts about ways and means.

But that could be excess pressure too!

[Jimgreen01]

Understood and I will test it. 

[Bfg]

As Peter W says there should be no crankcase pressure when there is a breather pipe being sucked via the carburettors. 

I'd recommend you check that the breather pipes and the Y-junction are clear (easily blown through) from either end.   Might I further suggest you remove the pipes from the air filters and run the engine (with oil filler cap on, perhaps with a piece of polythene bag tightly under it to ensure it is sealed ) ..for just a short while to see how much blow, if any, comes out of the breather pipe. 

4 cylinder engines have two pistons rising in their bores as the other two descend, which balances the pressure out.  Inside such an engine (inside the crankcase) there should be little or no positive (blowing outwards) pressure. On the contrary your engine's breather ..being sucked via the carburettors.. should cause negative crankcase pressure (very slightly sucking your hand to the filler hole).   

You may feel the blast of wind though (a whirlwind from the spinning crankshaft) as well as the splash of oil from the rocker arms.  Wind may be felt on the palm of your hand when placed over the filler cap hole (as Stuart suggested) but that's different to pressure  ..which is where you feel the palm of your hand being lifting off the filler hole.   Excess pressure is a sure sign of piston ring failure (worn or broken) or a deeply scored (scratched) bore.

P.  

[Jimgreen01]

P. Thanks for the detail. 
I have thoroughly cleaned the venting/breather pipes and Y-piece although frankly they were not too cruddy and definitely not blocked at all. 
So if I remove the pipes from the air filters and do as you suggest am I looking for air pressure (away from the cover) or oil or both?

thanks. 

[Jimgreen01]

10 hours ago, john.r.davies said:

A tester is cheap, and while detail essential, the method is simple.  

Warm up engibe, remove all plugs, fix throttle wide open, disconnect LT wire from coil.

Screw in tester, turn engine on starter unti guage maxes (4-5 turns)

Read guage.

Repeat on next cylinder.

Repeat whole test, until individual bore readibgs are consistent.

Good luck!

John

 

I’m assuming I need to disconnect the fuel pump also?

[john.r.davies]

Bfg,

"  Inside such an engine (inside the crankcase) there should be little or no positive (blowing outwards) pressure. "

The seal of piston rings on bores is never, never can be, perfect.  There is always ' blow-by',  gases leaking past, into the crankcase.   It can be about 1% of the gas vented down the exhaust pipe, even in a new engine.  If there were no such a leak, why is acrankcase breather provided?

John

[Jimgreen01]

Guys. Forgive my ignorance but to test the compression, do I need to disable the fuel supply? Disconnect the fuel line to the pump?