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Discussion Starter #1
Hi guys,

I had the turbo, egr, and several hundred poundsworth of work done to my megane about 6 months ago and ever since it seemed down on power,
After checking the pipes and cleaning basically everything, ive found the PCV to be at fault.

For those who aren't familiar its the round thing on the top of the engine connecting the pipe coming from the cranckcase and the pipe going into the top of the turbo.

Its supposed to be a one way valve from the turbo end but the rubber seal in mine has severely corroded and now just lets the boost pressure disappear and also allows a shed load of oil circulate through the pipes and fill up the intercooler, I was loosing oil at a rate of a litre/1000 miles. :crazy:

Now, to find a second hand PCV in good condition is tough (ive already been to 2 scrappys and neither had one) ive heard the part from Renault is about 60 quid,

My question is, is there any harm in blocking turbo pipe going into the pcv and letting the cranckcase pipe vent to atmosphere (im not to concerned about the trees and bunnies sorry). Will this put any strain on the turbo? does the turbo need the oily vapours for lubrication?

thanks in advance

Premium Member
6,369 Posts
The pcv or crankcase valve/hose is connected on the inlet side of the turbo(afaik).
So the pipe n valve would only operate on the air .
pressure inside the engine blowing to the vacuum side of the turbo.

The system should be designed to work with a bit of crakcase gas/oily vapour going past the turbo .
If you can get it to run better without the crankcase gas goin in to the turbo,great,but your not supposed to block off the crankcase breather or have it venting into the open air.The neg pressure differential of open air might not be enough to operate the valve efficiently(?).

My car:downstram of the turbo there is alip on the joint going in to the intercooler which allows excess oil(from the crankcase) to weep out under turbo pressure,to prevent oil filling up the intercooler..

If the engine was very worn or theis weep joint got blocked the amount of oil vapour and back pressure gas might allow oil to fill up the intercooler.

Burning/losing oil doesnt mean its all goin into the breather hose some may be burnt in combustion as well.
My diesel has to have special low ash oil for the dpf in the exhaust,so some oil /residue muct go out that way from new.
Oil consumption on mine was like 250 ml every 3months when new,it tightened up more after 15k but it still uses oil.

I just mean the turbo isnt blowing back air thru the hose and the engine is set to perform with a little crankcase gas comin thru.To get it to perform better without it might need some adjustment.
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