Hi all, searching for a vacuum leak, I attached a smoke machine to the brake boost port on the upper inlet manifold.

When I pump smoke in I am getting a bit of smoke from the valve end of the egr tube (leaking gasket), but I am also getting some smoke bellowing out from under the top hat on the egr valve itself, is this normal with the engine off I.e no vacuum being applied to the top port or is the diaphragm leaking in the valve?

You should be able to get your fingers in there and move a metal door that is attached to a spring. Sometimes corrosion inhibits the movement of the door, or maybe the spring is broken. It's not a perfect seal even when it is working correctly.

Yes I can get my fingers up inside and move the diaphragm, I just thought that if smoke came out from there it meant it wasn't sealing properly, and could be drawing unmetered air into the plenum.

If you have smoke coming out from underneath the top of the EGR valve where you can touch the diaphragm with your fingers, then you have a leak in the diaphragm and pintle. That's supposed to be sealed so that the EGR solenoid can open the pintle in the bottom.

Apply a vacuum to the EGR valve or push up on the diaphragm, cap the vacuum nipple with a finger and release the pressure on the diaphragm while keeping your fingers in contact with it. If you feel it moving down, then you have a leak. With a vacuum gauge, pull about 10 lbs and see if it holds.

Just tried with my finger over the nipple and after about 30 secs the diaphragm had dropped fully down again.

Thus it needs to be replaced.

I tested both my old valve and a new BWD valve for leaks around the shaft and both leak. I think that's just the way they are.

I won't buy another one just yet then, if a few others could try the finger over the vacuum port test, I would really appreciate it.

The finger test is what I always used until I got a Mighty Vac vacuum pump. You should know if it's leaking down within a minute. With the Mighty Vac I can pump up about 10 inches of vacuum, lay it down while I do something else then come back to see if it leaked down. If you have a good diaphragm and and a good seal on the nipple, it should never leak down, whether new or used.

Ok cheers, so it definitely sounds like it's no good then as it leaks down in less than a minute. I'll see if I can borrow the vacuum pump from the mech lads tomorrow just to be absolutely positive.

Wouldn't pull more than 5lb on the vac pump, and went down in about 20 seconds, so I've ordered a new one, I'll test it before I fit it to see how it compares.

Ok, I haven't tested the new egr valve with the vacuum pump as I'm off work for a week, but it definitely doesn't leak down using the finger test! So I just went ahead and fitted it and the valve and tube have now passed my smoke machine test 😃