"cause" of oil leak at head drain tube??

[tedtaylor]

HELP! I developed an oil leak (pretty bad) at the rubber plastic drain tube between the head and crankcase there under the carbs and above the fuel pump. I thought perhaps the plastic tube hardened over the years and cracked, but much to my dismay the leakage was coming from the uppermost connection to the head. I removed the tube and found it intact, no split, holes, or hardening for that matter.
With great care, i was able to replace with a new one, and get this.... without removing the head. I read elsewhere that it can be done and yes, i was able to do it, rather easily i thought.
I accessed it by removing carbs, intake plenum, fuel pump and distributor cap/wires and misc stuff about. I trimmed the bottom connection a 1/4 inch. I used vice grips (narrow pointy nose kind) to squeeze tube in the center for a "flex point" to better bend it into place. I used a generous amount of RTV sealant, inserted bottom end in first and flexed the tube via vice grips while pushing top under the head overhang, and presto! It went into place. A couple twist turns to make sure it was seated both top and bottom and additional RTV sealant around the outside edges and I'm finished.

Before I fully reassemble everything else back into place, i remember a good Lotus buddy "scaring" me saying that the reason the tube leaked oil was that my rings were bad. Now the engine runs super and the leak only appeared suddenly after a hard, winding it out, run with high revs. This gives his idea of bad rings some credence since it makes sense that if too much pressure built up in the head, it would have no place to go but seek a weak spot to escape.
So i'm asking questions of this group, should my oil cap breathe better? should i drill a vent hole in the valve cover as i've seen others do for a vent drain tube into a canister/collector? are my rings bad?? or was the tube seal old and dried out enough to spring a leak? will installing a new tube as i have done and sealed properly eliminate the problem? WHAT EXACTLY IS THE CAUSE OF MY OIL LEAK AT THE TUBE?

[CBUEB1771]

Ted,
The most common reason for a leak at this location is the top of the drain tube not being properly fitted into the cylinder head. This normally happens when the head is installed and it is not noticed that the tube has shifted out of position and become crushed by the head. You would have noticed this crushing when you took the old one out. I would also check the breather tube that runs from the side of the cylinder head, along side the rear carburetor and into the air box. (I checked your previous photos and see that you still have the original air box.) There is a filter screen soldered into the breather tube at the end which is inserted into the cylinder head. This screen might have become clogged which would prevent the breather tube from venting the crank case properly.

[Elan45]

Best way to ascertain the condition of the rings in your engine is with a Leak-down test. Do you have any racer friends who might have a tester. I believe I bought mine for just under $100, 10 years ago. You also need a compressed air source. I have a pretty small air bottle that I take to the track and I have used it to do an abbreviated test in the paddock. So, you don't need a big compressor.

Roger

[tedtaylor]

Russ, it appeared the original was properly installed, nothing misaligned, but i did notice some crumbling when i fiddled with it after it was out. The breather tube screen is clean and clear and air passes through it fine.

Roger, i don't have a leak down tester, but i will try that when i can.

I'm having a hard time believing it will be the rings since car runs perfectly and there was no prior leak until i drove it hard with high revs. What would a short "spirited" drive do to the rings suddenly?

[mbell]

Was it leaking anywhere else?

Mine was missing it's breather setup when I got the car and my original replacement setup was too restrictive, the result was oil blowing out of the dip stick. If yours was excess blow by I'd expect other oil leaks.

Are you running the standard breather setup? You checked the engine side? I pulled an old rubber seal out if mine today!

If checked it all out and you've swapped the tube I take it for a hard run and see what happens. Could also run with breather open to air to test.

[tedtaylor]

Russ,
no, not leaking anywhere else.
i have reassembled the new drain tube and fuel pump, but while i have the carbs off, i'm going to do a quick rebuild kit job to them (makes sense)
Once i'm back on the road, i'll post the status update.
thanks everyone.

[types26/36]

Its worth checking that the welsh/core plug is not leaking as its sometimes mistaken for the rubber tube leaking.
In the worst case the the plug can drop out altogether.

[Certified Lotus]

Ted, I was just going to suggest the same as Brian in his post above. My S4 had the same plug missing (see my rebuild post on my S4) and my oil leak was only after driving at higher RPM's, not idiling. Only way to replace is head off. I have the plugs in my shop if you need one.

If you want to check the condition of the plug (or lack there of) use an angled automotive swivel mirror and a flashlight to check it.

By the way, congrats on getting the oil tube replaced without taking the head off!

Glen

[tedtaylor]

Brian, Glen,
good suggestion and i inspected with mirror and it appears secure and in place, however while i have access (and the black RTV sealant) i think i'll spread some over the hole/plug for good measure.

I'm inclined to think the plug is NOT the source of the leak because it is located at the rearmost point of the head and would have leaked down the back corner of the head and block. My leak was most definitely coming from the tube. I don't think oil would travel forward toward the tube. Also, i have the weber head motor mount which raises my carb side of the engine in situ, which would again, likely dribble the oil down the block at the back corner if it were that plug.

[tedtaylor]

well i went to rebuild my Stromberg carbs prior to installation (while they were out), however i could tell they were super clean and previously rebuilt, so i just took them apart, thoroughly cleaned and reassembled.
I put everything back together again. I used some RTV sealant on that funky plug/cap at the rearmost end of the head as suggested.
Car is running and no apparent leaks so far. Of course i haven't taken it on the road for a full high rev test yet to check for oil leaks, however Problem i've encountered is it's running rough and LOUSY! It's the end of day today, so i'll pickup where i left off tomorrow and check everything. I think my issue is "balancing" the carbs. I also think my O-rings on plenum didn't seal properly when i reassembled them. it's real awkward and tight to fit and tighten everything due to the interior shelf there under the carbs in the way. it makes it nearly impossible to get a wrench or socket on the carb mounting plates to plenum. I had to install the 3-nut plates (with O-rings) first and then attach carb 4 nuts last, at least for the carb closest to the firewall.

I'll read up on the procedure tonight and give it a try tomorrow. I have a venturi velocity gauge tool that you place over the carb intake while running for balancing purposes. Initially, one carb shows measurement while idling speed, but other pins the floating bubble indicator and engine revs up? Somethings wrong. !@#$%^&*

[pharriso]

Ted, it's not clear from what you've written... are we talking Strombergs or Webers here?

[tedtaylor]

strombergs

[mbell]

I use:
https://m.lowes.com/pd/Kobalt-35-Piece- ... se/3387640

For fitting the carbs on my +2, just enough space to get it on lower nuts and get a few clicks on the rachet mechanism. Makes it pretty low hassle to get carbs on and off. I got the set on sale for $10, also useful for larger sized 1/4 drive sockets.

[tedtaylor]

SUCCESS!
just back from my test drive and no oil leak so far.
I jump on the interstate for some high rev driving and BAM, stuck in bumper to bumper traffic the next 2 miles to the first exit. Luckily, i was about to take the clover leaf and 180 degree back track over the interstate in the other clear direction. Never fails when you want to get somewhere fast. in the middle of the day no less...

I was able to fine tune and synchronize the carbs, but had to plug the vacuum line off manifold to do it properly. Ended with fairly smooth idle at 900RPM and equal sync of carbs. Then fitting my vacuum lines, the RPMs rose and rough idle. I have yet to fully sort the vacuum lines which include headlights, gas tank venting, charcoal canister, chassis frame and air box. Fun, fun!

otherwise, car ran great and no oil leaks, nothing strong coming from breather tube, dip stick or oil cap, so hopefully it was not piston rings after all.

Now for much needed maintenance - oil change, coolant flush/fill, final brake & clutch bleeding. The fun never stops!

[Certified Lotus]

Ted, I applaud your perserverience and trouble shooting abilities!

With the weather we are experiencing here in the North East we may have a few more weeks of sports car driving weather