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Crankcase breather valve - Induction/Turbo/Chargecooler/Manifold/Exhaust - The Lotus Forums Jump to content
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Mike6

Crankcase breather valve

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Having previously had a disasterous experience with a cheap oil catch tank I have been cleaning out the breather pipework and removed tons of oil up to the turbo. I now dangle the pipe from the crankcase breather valve under the car but today decided to take a look at the green breather valve thingy (its stamped 'M10 filtre'). I know they are obsolete having read earlier threads on this so I carefully took it apart expecting to find a one way valve (thats what it says in the Lotus Service Notes) but all I found was a series of metal discs with holes which were very grubby and presumably acting as a filter. There was no valve or anything which might act as a one way device. My car is a 1988 carb turbo so later ones may possible be different.

Has anyone else looked inside this device - is mine missing something and will the fact that air and possible debris could travel back up the pipe into the engine cause any problem.

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It's a Y junction.

Bottom goes to the crank case (looking from the back of the car to the front) - the right spout (largest) goes to the air intake and the left small nozzle goes to a check valve and onot the inlet manifold (vacuum).

This is so at idle the fumes are sucked into the manifold and at boost (positive manifold pressure) the large volumes of gas goto the air box.

Inside the green thing are just a few gauses and stuff, no check valve - the gauses are designed to seperate the oila dn the air....dont work very well though :)

I just take a large hose off the crank and rest it in the engine tray - job done (oh and blank the manifold vacuum line)

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And the pickup point on the airbox, don't forget to blank that too!

I'd put a filter on the end of the breahter hose though to stop any nasties from crawling up there when your parked up

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I didn't bother, I used to have a filter but no-one could answer sufficiently why have a breather filter there when the pipe runs about 2 feet downwards. It cant suck objects up into the pipe, all that happened was the filter gummed up with oil and became another restriction.

I do agree with adding a bung to the little inlet though :thumbup:

I've currently got a 22mm section of two elbows joined to a staight hose - gives ample ventilation, the engine tray is my catch tank :)

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Thanks for all the help. I have noticed that the small one way valve on the vacuum lines which goes to the carbs seems to work in both directions. Unfortunately couldn't get this apart so a job to tackle another day.

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Ah, thats not good, that means under boost the crank is getting part of the boost pressure too !

I'd fix that asap.

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Jonathon - Could this explain why I get so much popping and gurgling on overrun. However I have noticed that the Tpiece which splits the vacuum pipe into the carbs has some sort of one way device inside. It could be this was put in as the one way valve might be obsolete

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OK is there a way of venting these two without overpressuring the crank. My breather (air filter box end) is connected to a catch tank that has the other outlet piped to atmosphere down to the undertray and the lid it a vent also, so there shouldn't be too much resistance provided that the pipes aren't blocked with crud or kinked etc

Suggestions?

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Having started this post I didn't want any gunk getting back into the airbox after fitting a nice K&N filter. There are a lot if oil catch tanks on the maket but the pipe diamenter going in and out can be small leaving presuure build up in the crankcase which then blows out the dipstick or worse. To be effective the tank must have a pressure valve to prevent this - mine didn't and they are still being advertised for Lotus' on ebay.

I simply blanked off the hole on the air filter box put in a fairly large diamenter pipe on the breather and then run it under the car. Its mostly steam that comes out with a fairly small amount of oil.

The downside is that its not that envirmentally friendly but at least it stops the potential for oil droplets to go up the pipe via the filter to the turbo (not good). The trunking on mine was drenched in 20 years of oil and took ages to clean out. Some of this must have been getting into the turbo.

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