Servicing the CDR
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Joined: Apr 2006
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Servicing the CDR
I am cleaning out my cdr valve right now and i am wondering what it should look like inside, i read something about a diaphram, should i see this or what am i looking for? Thanks Mike.
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From: San Carlos, CA
I remember only seeing a spring mechanism that opens and closes the valve when you looked in. How dirty is it? Are you using gasoline to clean? There is a little hole on the body that alot of junk will come out of, make sure that it is clean. Don't forget, air dry only, no compressed air.
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From: Oregon
I asked about the CDR about a month ago, regarding how to know if it was working. I was told to blow into the small hole and feel the inside diaphram move the metal seat via the larger holes. I did and found out that the valve did in fact move. I had been concerned that the CDR may have been inop. FYI
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sailors30,
I did that too got chapped lips from the gas, was also worried that my wife might think I was a huffer - LOL
I felt that the diaphragm on mine was ok but was worried about the rest. To my surprise the spring seems stronger in the new one?
2jhanna,
If you seem to be using a little more motor oil or if your getting a lot of oil on the bottom of the air filter hold down bolt the CDR might not be closing when it should (about 2000 rpm) and sucks in a little more oil mist than it should.
I think folks confuse the oil mist they are seeing at the oil fill tube with blow by but if you put your hand over the tube (at least on mine) there's no pressure at all at idle, which there should not be because the CDR should be open below 2000 rpm.
I did that too got chapped lips from the gas, was also worried that my wife might think I was a huffer - LOL
I felt that the diaphragm on mine was ok but was worried about the rest. To my surprise the spring seems stronger in the new one?
2jhanna,
If you seem to be using a little more motor oil or if your getting a lot of oil on the bottom of the air filter hold down bolt the CDR might not be closing when it should (about 2000 rpm) and sucks in a little more oil mist than it should.
I think folks confuse the oil mist they are seeing at the oil fill tube with blow by but if you put your hand over the tube (at least on mine) there's no pressure at all at idle, which there should not be because the CDR should be open below 2000 rpm.
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From: Oregon
93 E 350,
Did you try "huffing" on the new CRD to see if it moved different from the old one.
I was concerned that the spring was too weak on my old one, since it didn't appear to have much spring to it. Matter of fact the spring did not touch the moving brass diaphram cover unless it was huffed on. Just sorta rattled around in static conditions.
Thanks in advance.
Did you try "huffing" on the new CRD to see if it moved different from the old one.
I was concerned that the spring was too weak on my old one, since it didn't appear to have much spring to it. Matter of fact the spring did not touch the moving brass diaphram cover unless it was huffed on. Just sorta rattled around in static conditions.
Thanks in advance.
They must not seal 100% or the blowby would push all the gaslets out. 
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From what I got out of fooling around with mine is the newer CDR valve took a little more huffing to get it to close that's why I think the spring is stronger. On the old CDR I took an air regulator and turned it way down to may be a to a pound or so and put the nozzle by the small hole. What I found was if you blow (reverse huffing) into the end that goes to the valley pan, once you get a little pressure on it the valve will open and let air past. I believe this is where the Rotunda back pressure gage comes in – check the specs if bad replace the CDR valve or you’ve got too much blow by?
