Escort CVH Breather

Escort Upgrades - CVH Breather System

During the production run of the 1.6 MFi CVH engine a number of revisions where carried out to the crankcase ventilation system. These modifications were carried out to try to combat problems with stalling and rough idleing that was being caused by oil contamination of the throttle housing from the crankcase venting system.

Before carrying out this modification you need to make sure the rest of the breather system is in good order. The breather hose from the front of the airbox to the rear drivers side of the cylinder head rocker cover must be checked for blockage as must the breather hose at the back of the block on the near side running from the bottom of the crank case to the rocker cover. These two apertures in the rocker cover themselves must be checked clear of blockage as they are often full of crud. The connection at the base of the block is also prone to guming up and must be clear. There is however a baffle behind this aperture so care must be taken.

On the MK3 cars, there were two versions of the breather system with the second version being introduced to try to overcome these problems but they weren't completely eradicated until a redisgned throttle assembly was introduced with the MK4 cars.

Rather than mess about explaining the earlier versions I'll go straight to the latest spec, especially as parts aren't going to be in numerous supply down the local scrapyard.
First you need to source a throttle housing from a MK4 MFi car. This can be identified by a small idle adjustment screw on top of the housing with a tamper proof cap as opposed to the large thumb wheel adjuster mounted under the throttle housing on the earlier version.Clean up the throttle housing and check all passages are free from blockage. Fit this in place of your existing throttle housing. This does of course mean you'll probably have to adjust the idle screw.
Whilst you're there, retrieve the hose connector from the drivers side of the plenum chamber and the hose coming from it. You'll also want the small length of pipe connected to it ant the three way plastic adaptor as shown.

Mk4 MFi

Mk3 MFi

Plenum connection, three-way adaptor and pipes.

You'll find a blanking plug on the drivers side of the plenum chamber that you'll need to remove and insert the newly aquired hose connector. Discard the Filter and replace with the plastic adapter. You may have a small pipe running from the filter you have just removed across the front of the plenum chamber to a 'T' piece. Remove this pipe, the 'T' piece and the short pipe connecting the 'T' piece to the throttle housing end of the plenum chamber and discard. Connect the now free floating small diameter pipe directly to the plenum chamber.

You should now have a set up similar to that shown below. The MK4 throttle housing and the near side plenum brether plumbed via a large diameter pipe to the auxiliary air device as normal and via a small diameter pipe directly to the over run fuel shut off valve (cylindrical unit on back of air filter lid). The drivers side plenum chamber breather should be attached to the new adapter in place of the filter which should in turn be connected to the rocker cover and via a long length of hose to the front of the air filter lid/fuel distributor unit.

Basically, the nearside plenum chamber breather is taken out of the breather circuit and used solely as a tapping for the running of the engine (auxiliary air device and overrun fuel shut off valve). A new tapping is made into the drivers side of the plenum via the new hose connector which takes over the role of crankcase venting. The new throttle housing moves the idle air passage from the bottom of the housing where it it prone to blockage from contaminants to the top of the housing.

Job Done!

The contents of this website are purely a reflection of my own experiences and knowledge gained whilst working on my various projects. Anything you do based on what you have read here is done so entirely at your own risk.
Personally I wouldn't trust someone like me with a lawn mower! You have been warned! Flapper-bat!