Jump to content

Open Crankcase vent - how much oil leakage ?


Recommended Posts

Hi All, 

I do have an open crankcase vent on my TR2 (TR4A engine). After a drive, I do have a little oil puddle building up under the car under the vent hose.

I have measured the cumbustion pressures which are all well around 11 bar, so no reason for concern.

So my question: how much oil would be considered to be normal with an open vent ? Any recommendation for modification  optimization?  I may think about retrofitting a closed system ....?

Input welcome!

 

Thanks

Cheers

Oliver

Link to post
Share on other sites

Hi Oliver,

normally the open vent (Snorkel) does not cause concern regarding passing oil.

How much oil do you normally have in the crankcase.  If it is near the full mark then you will use oil somewhere.

Consider having the oil up to the 1/2 way point.

 

Roger

Link to post
Share on other sites

Which oil filter type do you have?  Is it the original type?

My car does the same as yours and it is oil dripping from the bottom of the oil filter where the bolt goes through.  
 

Item 19 here
 

Peter W

2D9C2689-E647-42BD-9EF5-469A39ECB9F3.jpeg

Link to post
Share on other sites

Hi All, 

Thanks for the feedback.

I do have the oil level at 1/2

I do still have installed the org oil filter (may fit the can conversion kit with the next oil change). But I am quite condident, that the oil is coming of the vent snorkel. It only drops max 1h after parking. Wiping the puddle away will do it .... until the next ride.

Cheers

Oliver

Link to post
Share on other sites

You are running a breathing oil filler cap on the rocker cover...right ?

The "snorkel" breather vent at the bottom of the crankcase cannot pass direct oil flow becaus it has a vertical baffle plate in the wall (unless the sump is overfilled , which it isn't because you say it's half full ), so any oil dripping out of there is because of positive pressure in the crankcase mixing the oil up and breathing past the baffle and out through the snorkel. 

Mick Richards

Edited by Motorsport Mickey
Link to post
Share on other sites

Hi Mick, 

Correct, I have the a breathing oil filler cap installed. I have cleaned it today to make sure is not plugged...

I think there must be an overpressure  in an open system as there is no suction from anywhere . You only have depressure with a closed system to my understanding....

With the compression being perfect on all cylinders, I do not have an explanation why the crankcase pressure should be higher than normal....

Should I suspect the snorkel to mayeb not have the  vertical baffle plate in the wall ?

 

Link to post
Share on other sites

"Should I suspect the snorkel to maybe not have the  vertical baffle plate in the wall ?"

Unlikely I should think, the baffling in that area ia all part of the block casting, although maybe worth dropping the sump to have alooksee. You could also check out what ever gubbins can be inspected that could possibly give you an over pressure.

You say you have a TR4 engine in, have you any idea what's been done to it ? has it got a Marx rear lip seal added to the crank for example ? These engines are not sealed against atmosphere normally,  even the crank doesn't have a seal at the rear it having a scroll recirculation scavenging system fitted. The rear oil scroll ( a thread like machined surface in the crank behind the main journal) is skimmed ( a couple of thou above the scroll) by the alloy rear oil scroll seal which has a similar thread like machining in it. This removes any excess oil and channels it back into the sump (whilst the engine is turning, (when it stops the oil escapes through the gap) and works surprisingly well...for decades until the engine is rebuilt and the rear alloy scroll is refitted too close to the crank surface, (the workshop manual specifies it incorrectly) which machines it and the oil is now unrestrained and escapes from the rear of crank. The Marx rear lip seal is an excellent piece of kit which fits behind the oil scroll and prevents the oil seeping out there, normally giving a dry engine at the back. 

Mick Richards

Link to post
Share on other sites

I’m with Peter on this one.....check that the oil filter canister bolt is not the culprit. Clean sweet of paper placed under the two suspects, the snorkel and the filter bolt. Use s plumb line to check which one offending once you have oil on the paper.

The rubber bolt seal in the end of the filter canister is the usual problem.

Iain

Link to post
Share on other sites

I used an old master cylinder seal (Never throw anything away) and a slightly dished penny washer to seal where the bolt goes through the canister, and this seems to work.

Charlie.

Link to post
Share on other sites

A drip or two is normal. The pipe is venting crankcase fumes so a bit of oil collecting in the pipe and dripping out after stopping is to be expected. If it is more than a drip or two it still might be normal. One of my TR2s has a new engine and after a long fast drive it will drop a drop or two. My daily driver might drop a drop or three.

Link to post
Share on other sites

During my sprinting phase our '3 had a catch tank connected to the sump breather (as required by the regs) - I was surprised that some oil accumulated there even during normal motoring. Assume all the TR4 EGR gubbins has been removed and that you are not parked on a steep hill.  Also that it is the correct up-n-over breather and not just a right angle pipe.

Link to post
Share on other sites
  • 3 weeks later...

The later engines such as the 4A had a closed circuit breathing system with the crankcase vent closed off with a plug. Are you sure that the crankcase breather does not still have a plug in it?

I have a TR4 block in my TR2 and which had the snorkel fitted to the crankcase vent. In the process of fitting a oil catch tank to comply with the sprint regs I did a last minute check to make sure that vent was clear and discovered that the plug was still installed. Whoever had installed the engine didn't check and had just stuffed the snorkel in the hole. The plug was pushed deep into the vent and you may have to drop the sump to check.

Prior to doing that, there had been quite an oil leak at the rear of the sump, presumeably past the crank seal, but opening up the vent reduced the oil consumption and the oil on the floor is now much less

 

Phil

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.