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Basil
06-03-2006, 06:18 PM
I have rebuilt the motor in my Spitfire and ever since I have been getting oil out the rear seal like crazy. This is despipte replacing the rear seal- twice! When I rebuilt the motor I put new .030 oversized pistons in and I'm wondering if I installed the rings incorrectly could that cause too much crankcase pressure which, in turn, could be causing my oil leak out the backside?

Basil

Brosky
06-03-2006, 07:48 PM
Start it up and take out the dipstick. Any sign of blowby coming out of there? Next remove oil filler cap and see what happens if you put your hand and a rag over to seal it up. Any pressure there? You may have to rev it up when you do these checks to get results.

Harry_Ward
06-03-2006, 08:06 PM
Basil,

Good assumption does it flow more when it's running or the same when shut off. Did the leak occur immediately after initial start up. Are the seals you are using original old stock or of new design currently manufactured. Did you lubricate the seal with oil before install. Check the valve cover for blow out through the fill cap. Check for plugged vent on valve cover. Seal may be getting distorted or cut on install. Ok stretching there but you never know.

Questions questions, never any answers,
sorry!
Harry

Basil
06-03-2006, 09:39 PM
[ QUOTE ]
Basil,

Good assumption does it flow more when it's running or the same when shut off. Did the leak occur immediately after initial start up. Are the seals you are using original old stock or of new design currently manufactured. Did you lubricate the seal with oil before install. Check the valve cover for blow out through the fill cap. Check for plugged vent on valve cover. Seal may be getting distorted or cut on install. Ok stretching there but you never know.

Questions questions, never any answers,
sorry!
Harry

[/ QUOTE ]

It probably leaks when its running but just gets tosses about, but for sure right after I shut it off I get a nice stream of oil from right where the rear seal is immediatly after I shut it off. It will stream out for a few seconds then slow to a drip and stop - until next time I run it. Its the only problem that is keeping me from enjoying my Spit!

Basil

piman
06-04-2006, 07:04 AM
Hello Basil,

from your last comment I don't think that the rings are the problem as it sounds like pumped oil from the rear bearing is escaping out of rather than back into the engine.
If that is the case then I would say that it must be a very serious oil leak? It's a long time since I had a Triumph engine apart so don't remember all the details of that area. Guessing I would be looking for a blocked oil drain etc because bearing in mind some engines don't even have seals in that area.

Alec

tomshobby
06-04-2006, 07:29 AM
Hi Basil,
Yes it could be blow-by. Like Brosky said you can get an idea if it is by taking off the filler cap while the engine is running. If funes are coming out then lay something like card stock over the opening to see if it has enough pressure to lift it slightly. If all is well it should pull slightly.

By any chance did you check end gap in the rings before installing them on the pistons? Just to see they fit the bore properly. Did you stagger the ring gaps?

In any case, give it a chance. Let the rings seat and see if the problem continues after a few hundred miles. You know that pretty cross hatch pattern the machinist makes when he hones the cylinders, that is to wear the rings slightly and seat them. The idea is for the cylinders to be worn smooth and the rings to become seated togather.

Paul Johnson
06-04-2006, 09:05 AM
I cannot see the rings as being a problem, but will listen with an open mind if someone can explain that.
If the rings are very loose, and oil is getting past them, then you would be burning it with a large trail of blue smoke, as the oil would enter the combustion chamber.
You most likely have one of three things:
1. oil seal installed incorrectly, or incorrect seal installed.
2. no crankcase ventilation which forces the oil past the weakest point.
3. abnormally high oil pressure relief tension.

Make that four.

4. Have a good hard look to be sure that the oil is not coming from some external source and only appears to be at the rear main.

Good luck - we anxiously wait to hear final results, though probably not as anxiously as you.

Basil
06-04-2006, 11:11 AM
Thanks for all the feed back guys. There are a lot of good ideas here. The only reason I was thinking of rings is on a hunch that they are not installed properly or don't have the correct gap, etc., so that it caused excess Crankcase pressure. I “thought” I had checked the gap and staggered them, but its been awhile so maybe I didn’t? (Would a compression check show anything here?)

As for the seal, I have replaced it - twice. I suppose there is a chance it is the wrong seal, but it "seemed" to fit correctly. The idea of the blocked oil drain at the rear bearing is something I had not considered, and I did in fact install new Mains when I rebuilt the engine.

I’m wondering if my best bet at this point isn’t to just do a tear down and check each of these carefully as I put it back together again.

Harry_Ward
06-04-2006, 11:16 AM
Basil,

Had some more thought...still raining, seal housing gasket worn or seal housing may be distorted, crankshaft end may be worn. In theory I guess crank vent pressure could build due to ring installation if one of the compression rings were to be installed upside down but this should vent and be fairly obvious. Try performing a leak down on each cylinder and see if rings doing the job. If this proves good then I doubt it's the rings. I like the rear main end bearing oil journal being blocked, worn? (hopefully partially) theory as well but look for simple first.

Good Luck,
Harry

BTW, when you do pull it all apart try to get the seal out without damage and maybe you will be able to tell if it blew out or wore out due to friction (heat).

DNK
06-04-2006, 12:14 PM
Your Emporiorship-Wasn't it here I saw a thread about new improved rear seals that ended up having the wrong instructions with them?
Don

tomshobby
06-04-2006, 12:46 PM
Lots of good things here. Like Harry says, a leak down test or doing a second test with a little oil in the cyl.

I still think it might not hurt to drive it some and see what happens. It might clear up or become easier to find, or, the answer might come to mind because of something you did or did not do while working on it in the first place.

My TR6 was blowing back and leaking oil out from the filler cap and I think consuming some when I first started driving this spring. Actually a pint every fill up. After 1200 miles it is hardly using any oil and only an occasional spot in the garage.

If it is not so much that it endangers the engine and you can add at fillups then putting on a few miles should not hurt anything except for cleaning the drive or garage floor.

Well, maybe the guy following might not like the oil spots on his windshield! /ubbthreads/images/graemlins/grin.gif

piman
06-05-2006, 02:04 AM
Hello Basil,

being in danger of repeating myself, from your description:-

"It will stream out for a few seconds then slow to a drip and stop"

How can blow-by cause this to happen on a stopped engine?
As an aside what oil pressure do you have, any more than 45psi at 2000 rpm plus hot is too much.

I suggest you will need to dismantle the engine again and look critically at the rear main bearing assembly.

Alec

Basil
06-05-2006, 08:01 AM
[ QUOTE ]
I still think it might not hurt to drive it some and see what happens.

[/ QUOTE ]

I've actually put quite a few miles on it and the problem persists.

Basil
06-05-2006, 08:02 AM
[ QUOTE ]
Hello Basil,

being in danger of repeating myself, from your description:-

"It will stream out for a few seconds then slow to a drip and stop"

How can blow-by cause this to happen on a stopped engine?
As an aside what oil pressure do you have, any more than 45psi at 2000 rpm plus hot is too much.

I suggest you will need to dismantle the engine again and look critically at the rear main bearing assembly.

Alec

[/ QUOTE ]

Where would I hook up an oil pressure gauge on a Spitfire to see what sort of pressure it has?

And your probably right that I need to pull it and look at those mains. I had that part of the engine done by a machine shop (who I presumed would know what they were doing...but). Not somethign I loook forward to but it may be the only solution at this point.

tomshobby
06-05-2006, 10:58 AM
Basil, I did not know you had some miles om it. I knew it was an outside chance but one could only hope.

Alec is right, only one thing to do. /ubbthreads/images/graemlins/frown.gif

Andrew Mace
06-05-2006, 11:10 AM
[ QUOTE ]
Your Emporiorship-Wasn't it here I saw a thread about new improved rear seals that ended up having the wrong instructions with them?
Don

[/ QUOTE ]I don't believe that applies to Spitfire motors; rather, it involves the wet-liner four-cylinders used in TR2/4.

Meanwhile, Basil asked:[ QUOTE ]
Where would I hook up an oil pressure gauge on a Spitfire to see what sort of pressure it has?

[/ QUOTE ]I'd use the same spot where the idiot light sender is now: LH side of the block.

BTW, what vintage Spitfire IS this?

mailbox
06-05-2006, 12:55 PM
I have little to no specific knowledge of Triumph engines, but going by your description of the oil leakage, my vote goes with a blocked drain at the rear seal. It sounds like too much oil pressure on the rear seal is causing blow by at the seal. If you had that much blow by at the rings, I believe you would have a hard time keeping the dipstick in. Oh well, it's my $.02 worth. /ubbthreads/images/graemlins/grin.gif

Darwin
06-05-2006, 08:38 PM
Bas,
If you have to open the engine again, check the end of the crankshaft where the oil seal rides. Mine had a quite a bit of wear in that area. I had some professional mechanic buddies tell me to just use extra block to seal housing gaskets to re-position the oil seal on to a smoother part of the crank. Don't know if it will work as of yet but makes sense to me.

Basil
06-05-2006, 10:28 PM
[ QUOTE ]
Bas,
If you have to open the engine again, check the end of the crankshaft where the oil seal rides. Mine had a quite a bit of wear in that area. I had some professional mechanic buddies tell me to just use extra block to seal housing gaskets to re-position the oil seal on to a smoother part of the crank. Don't know if it will work as of yet but makes sense to me.

[/ QUOTE ]

Yeah, I have heard that also. When I pull it apart this time I will certainly mic the crank.

Basil

aeronca65t
06-05-2006, 10:50 PM
The aluminum piece that holds the rear seal on in these engines is prone to warping. I had a bad one on my car. And one of the bolts that held it in was stripped.
My experience is that these engines will ooze oil if they do not have some sort of PCV system. Even my racer has a home-brew PCV system. When I first used it for racing, I had a simple road draft tube and it leaked oil for the rear seal area. The PCV system solved that.
If it's not burning excess oil, your rings are not likely to be causing high crankcase presssure.
And be sure the pan is not warped...this can cause leakage too.
Finally (and I hate to admit this), I use *plenty* of silicone gasket sealer around my oil pan, along with a new gasket. My engine doesn't leak a drop.

Basil
06-07-2006, 08:46 PM
I've decided to do what I shoudl have done all along. I'm taking it to the base hobby show and putting it up on a drive-on lift and getting user it while its running. I may add some of that "stuff" you add so that a UV light will show where stuff is coming from. I'm hoping it is just something simple like a warped seal housing or similar simple fix. Ooze I can handle, its this pouring out that gets old! /ubbthreads/images/graemlins/tongue.gif