what does a Brake Booster Check Valve actally do?

[wymondham1979]

Hi guys after reading several posts on crankcase pressure, oil leaks ect I was thinking of fitting a Brake Booster Check Valve but abandoned the idea as availability of anything like that in the uk is limited As you probably know we are still on rationing over here LOL
but a mates boss was in the USA and kindly picked me up a couple
Hope they are the right part 80190 dorman


can someone explain please ,what it does ,where to put it (and will it invalidate my insurance as a performance part LOL)
thanks

 

[pamcopete]

wymondham1979,

The brake booster check valve is used in cars with a vacuum booster for the brakes (power brakes). It is essentially a one way check valve which allows air to only go in one direction. It is installed in the vent hose on the upper rear of the engine and works by allowing the air under pressure from the crankcase to go through the valve, but does not let any air go back to the crankcase, resulting in a very slight vacuum in the crankcase. This low pressure in the crankcase then will cause air to enter the crankcase through leakage around the various seals in the engine instead of the oil leaking past the seals resulting in a leakless engine as far as the seals are concerned. It will not, however, compensate for a gusher.

Although the valve normally operates as a vacuum check valve, this application uses the valve in reverse to allow the air from the crankcase to blow through the valve, leaving behind a small vacuum in the crankcase. So, the round base of the valve goes towards the engine and the skinny barb is the exit for the crankcase air.

My only concern is that by creating a small vacuum in the crankcase instead of the slight positive pressure that is the norm, you may be affecting upper cylinder lubrication which depends on a combination of vacuum in the combustion chamber and slight pressure in the crankcase to force the oil into the rings. Every time I raise this possibility, however, people shout at me, and there have been no reports of shortened engine life due to using the valve.

 

[5twins]

If you're going to run pods, poise the valves over the top of them. Any oil mist or drips they emit will be recycled back through the engine .....

 

[sseres]

but if you wanted to keep the stock airboxes, would I just put one of these in the hose somewhere inline in the breather hose?

 

[XSLeo]

On the later bike with the breather going into the stock air box you don't need the brake check valve. The air box serves that function. As the pressure in the crank case goes out the hose ti the air box the incoming air flow creates a vacumm to draw this pressure out of the engine breather and draw it back into the engine.
On the earlier bikes the breather just vented to open air. These as well as those later bikes without the stock air boxes can use the check valves.
Leo

 

[5twins]

Yes, I don't see the need for them if you have the stock set-up where the breather hose(s) connect to the airbox. With pods, you gotta do something with that breather hose and this seems to be about the simplest, cheapest, and cleanest solution. I started out with just a little K&N filter on my breather hose. It was messy, always oily.

 

[retiredgentleman]

Yes, the vent hoses going into the stock air boxes works very well. I just removed my air boxes and there is not even any oil present.

 

[payaso13]

Wow I just finished putting on uni's and check valve...huge difference from air box....with air box I would have to hold slight throttle till it warmed up...then it would idle fine...now I start it and right off the bat smooth idle...just got to fine tune to make sure mixtures are good...but very happy with results

 

[davetherave]

I Got mine in the UK from ebay £6.50 + £3.75 Postage

http://www.ebay.co.uk/itm/Jeep-YJ-W...496-1987-95-/231448964700?hash=item35e36eee5c

Came in a massive bag.
See valve bottom right.