TR4 SUDDEN OIL LOSS

[Willie]

To answer Raalph and Hamish:

My air filters are the standard wire mesh type capable only of filtering out bumble bees!

The oil level was checked almost 2 weeks after the run with everything cold. The dipstick is solid - no movement of the cap and seal, and is sitting aat the same level as always.

I checked the top pipe from rocker box to carbs earlier and confirmed no blockage by blowing through.

Willie

[Motorsport Mickey]

I’m with Alan BW, you need a compression check to see if you have broken a ring which has caused the oil to be pumped down and out the exhaust.
Alternatively check the PRV (pressure relief valve) on top of the filter housing,  if it’s stuck or the valve spring weakened it will pump large quantities down the exhaust exiting in a fine haze and not too much smoke easily missed. You won’t get much in engine exterior oil leaks, it easier to get out down the exhaust.

Mick Richards

[Willie]

Thanks Mick. Alan only lives 3 or 4 miles away and has a tester, so I'll see what we record and feedback in this discussion next week.

Willie

[Lebro]

No PRV fitted as far as I can see, just direct from rocker cover to air filters.

Bob

[BlueTR3A-5EKT]

What oil is your engine being filled and topped up with?

I had problems with high oil consumption when using cheap 20/50.  Having changed the oil to a branded 20/50 (Millers Classic) the oil consumption dropped noticeably.  Pressure is maintained when good and hot too after an hours run on the motorway.

Peter W

[Motorsport Mickey]

32 minutes ago, Lebro said:

No PRV fitted as far as I can see, just direct from rocker cover to air filters.

Bob

Sorry Bob, I think I misdescribed it. I mean the pressure regulator valve with large ball bearing and spring on the oil filter head.

Mick Richards

[Willie]

Bob, what PRV should there be? I have one in the servo line, but not the breather.

I decided to go nostalgic - Duckhams 20/50 in the sump.

I do have the Moss rocker feed braided hose hose from oil gallery to top of head.

Would the PRV jamming affect the oil pressure gauge reading? My engine runs at 70 psi at cruising speed.

Willie

 

[Motorsport Mickey]

If your pressure gauge is varying throughout the range and giving 70 lbs at over 2000 revs I would expect it to be ok. Just the compressions to check then.

Mick Richards

[stuart]

31 minutes ago, Willie said:

I do have the Moss rocker feed braided hose hose from oil gallery to top of head.

 

Willie

 

That may contribute if its fitted without a restrictor as it brings a lot more oil up onto the rocker gear and without valve stem oil seals you can get more oil drawn out

Stuart.

[Lebro]

The additional oil feed to the rockers is not necessarily a good thing, it can starve the bearings which need it most, & encourage burning oil via the valve guides.

General opinion on here (as far as I am aware) is - don't bother fitting it.

Bob.

 

Stuart beat me to it !

Edited May 14, 2021 by Lebro

[Willie]

I feel a restoration brewing! Good info - thank you! 

2 pics attached showing oil pressure at 800 rpm and 2000 rpm.

Willie

[Motorsport Mickey]

“I do have the Moss rocker feed braided hose hose from oil gallery to top of head.”

That’s a good spot, I hadn’t noticed that in the prose. As reported above unless you are spending lot’s of

1 minute ago, Willie said:

I feel a restoration brewing! Good info - thank you! 

2 pics attached showing oil pressure at 800 rpm and 2000 rpm.

Willie

Aaaahhhaa.....the culprit.

800 revs should be showing considerably less, about 20lbs from memory. The continual showing of 70 lbs at 800 and 2000.revs sez ... something wrong.

Has it been adjusted recently ? Maybe by a garage ? Or the oil feed to the rockers only fitted recently ? The pressure valve is either stuck or had been wound up, it’s blowing the oil out through the exhaust.

Mick Richards

[Willie]

Oil filter housing not touched, and oil feed to rockers hs been there for several years. It did increase oil consumption. Any simple advice on how to adjust the setting on the PRV?

Willie

 

[Motorsport Mickey]

Yes, check out the workshop manual for the method... which broadly says “ undo the lock nut and using a large bladed screw driver turn the adjusting screw either way until your pressures are set at 70 lbs at cruising speed falling to 20 lbs ( from memory) at tickover ( the 800 revs). The correct figures are available in the manual.
 

Because the problem has arrived without any contributing work happening on the engine, I should suspect an internal problem near the screw/spring/ ball bearing area. I had low pressure for a couple of thousand miles ( no forum available those days) which caused inadvertent rustproofing of following cars in the oil haze, before I found a chunk of carbon the size of the Hope diamond stuck in the spring. Remove the items and clean, if any rust on the ball ( unlikely, it’s routing oil) then clean off with Emery and refit. If nothing obvious the spring could have relaxed and need replacing ( normal suspects).

Mick Richards

Edited May 14, 2021 by Motorsport Mickey

[Willie]

Thanks Mick. The manual just refers to oil pressure rising to 75psi then displaying 70 psi at 2000 rpm.

 

Willie

[John L]

Doesnt the banjo bolt into the head of the external feed act as a restrictor, if it has the correct size hole in it, but how small should it be?

John

[stillp]

Doesn't the pressure relief valve just control the maximum pressure? Does it really have any effect on the tickover pressure? And why would a decent oil pressure at tickover be a bad thing?

Surely if the PRV has been wound up Willie's pressure would be higher than 70 psi at 2k rpm?

Pete

[stuart]

49 minutes ago, John L said:

Doesnt the banjo bolt into the head of the external feed act as a restrictor, if it has the correct size hole in it, but how small should it be?

John

No it doesnt. It shouldnt be any bigger than about 1mm but better not to use one at all.

Stuart.

Edited May 14, 2021 by stuart

[Motorsport Mickey]

1 hour ago, stillp said:

Doesn't the pressure relief valve just control the maximum pressure? Does it really have any effect on the tickover pressure? And why would a decent oil pressure at tickover be a bad thing?

Surely if the PRV has been wound up Willie's pressure would be higher than 70 psi at 2k rpm?

Pete

Not if the spring is ‘ Jack Jones’ ( buggered) and yes a “to high” pressure is not what these engines need. Flow is what’s required, otherwise the manufacturer would say 70 lb at 800 revs.

Mick Richards

[Motorsport Mickey]

1 hour ago, stuart said:

No it doesnt. It shouldnt be any bigger than about 1mm but better not to use one at all.

Stuart.

On 4 cyl race cars we use a 1mm restrictor inside the camshaft towers and that’s when we use up to 7000 revs. That’s so the oil stays where’s it’s needed around camshafts and crankshafts and not drowning the rocker shaft and valve stems.
So how much oil do we think should be pushed through these add on hoses at 3500 revs as we argue that it’s not...that windy with the top down ?

Totally not needed.

Mick Richards 

[Willie]

The rocker roil feed will be history tomorrow and before I adjust the oil pressure relief valve. I've located the original plugs!!

I'd like to express my sincere thanks to everyone who has contributed. Fantastic knowledge and preparedness to share with an enthusiastic amateur. I hope the discussion has been useful to others.

I will update when I have checked the compressions

[stillp]

2 hours ago, Motorsport Mickey said:

Not if the spring is ‘ Jack Jones’ ( buggered) and yes a “to high” pressure is not what these engines need. Flow is what’s required, otherwise the manufacturer would say 70 lb at 800 revs.

Mick Richards

Mick, I agree with all that, except maybe the last part, but since the pressure depends on the pump output and the restrictions to the flow that come from bearing clearances, etc, I can't see how any failure mode of the spring could make the pressure higher at tickover.

Regarding the last part of your statement, the manufacturer is, surely, stating the minimum pressure that is acceptable to provide sufficient flow, not a 'target' figure.

Pete

Edited May 14, 2021 by stillp

[Lebro]

I agree with Pete on this one. I would be looking for a restriction in the oil flow somewhere causing the unusually high pressure at low revs. maybe a kink in the oil pressure gauge feed pipe. Does the pressure drop at tickover if left for a while ? Could the filter be clogged causing the increase.

Bob

[barrytr4]

Hi Mates

here 's my two bobs worth, the dipstick is at the front, say,  car  was very slight down hill  when topped up, and very slight up hill when rechecked, that would be a big difference, the car needs to retested after  another  run , it can only leak or burn, if nothing has been adjusted ?, could have a broken oil ring?--Barry

[Willie]

Update....oil feed to rockers now removed. Engine from start up hit 60 psi at 850 rpm with choke. When temperature was in the 70 degree zone, 60 psi at tickover, rose to 70 psi at 2000 rpm! That's the target! See shot taken earlier. Do I need to adjust anything?

As a matter of interest, does anyone know the AF spanner size for the PRV adjuster locknut? Looks to be just under 1" AF.

Willie