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Un-deleting my CDR (Valve found thanks SteelSoldiers) looking for 1" Neoprene Tubing

Z

Zen Diesel

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College Park, Maryland
Un-deleting my CDR (Valve found thanks SteelSoldiers) looking for 1" Neoprene Tubing

I will have to go back and look but I think this is my first real post on this forum. I have been a long time lurker and I even joined SteelSoldiers so I could look at the picture attachments easier. But I try not to post on the internet unless I have a valid question or something to contribute.

Well after 8 years or so I finally pulled the trigger on buying my 1985 CUCV Banks Sidewinder with a 4L80E and electronic trans computer. My second military vehicle I previously had an 406 DOKA UniMog. However my move into the Sierra Nevada mountains made a naturally aspirated diesel tug an impractical option. So I was looking for a turbo charged military truck that could be a daily driver and offroad capable. I spent MANY MANY hours reading these forums and learning as much as I could about these trucks so I would have a pretty good idea of what I was getting into. Just an incredible resource of information this website is. I have a list of project that I plan to complete on my truck to fix the known issues that you folks have diagnosed and created workarounds for. So before I get to my question I wanted to thank you folks for all the time and effort you have put into keeping these old girls running and sharing the information.

My truck is a little bit of a basket case and I bought it non-running on eBay. I don't mind all of that. I enjoy working on my vehicles and working through the problems has forced me to read the GM technical manuals for these engines and become more familiar with my truck. While I was going over my engine examining the modifications I noticed a port was electrically taped off on my Banks air filter. My oil filler tube port was open to atmosphere and 2 ports on the intake were capped off. Red flags went up and I started to dig around the GM 6.2 training manual and read up on the theory and operation of the emissions system and found that my CDR had been deleted. I searched the forums and found an excellent post from jdemaris with crossreference Delco part CV910. Found a great deal and it will be heading my way in 2 days. What I couldn't find are the hose that goes from the oil filler tube to the CDR. That is a discontinued part from GM and I couldn't find any crossrefernces. I found similar shaped parts but without dimensions its nigh on impossible to guess dimensions from a line drawing or picture.

I consider myself pretty good at searching the internet and looking for workarounds but I could not source 1" ID Neoprene tubing anywhere in quantities below 50 or 100 feet. All of the heater hose I could find in the 1"diameter was either EPDM or Silicone which are both nogo for hydrocarbons. I found and industrial supplier for nitrile tubing that could withstand a mild vacuum and again $100 minimum order for 25 feet of hose. I'm not worried about the pre-molded part if I can find an appropriate hose I can either make it semi rigid to prevent kinks or strategically use fittings to route it through my engine. I am really curious if anyone else has run up against this problem and if so how they solved it.

Thanks
ZD
 
Z

Zen Diesel

New member
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Location
College Park, Maryland
Absolutely! I already contacted Banks to get the hose that runs from the CDR to my air box so the hose for the oil filler to my CDR is the last piece of that puzzle. How do we do this?

Thank you!
 
cucvrus

cucvrus

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Z

Zen Diesel

New member
21
1
3
Location
College Park, Maryland
On the 6.2 "Intake vacuum acts against a spring loaded diaphragm to control the flow of crankcase gases. Higher intake vacuum levels pull the diapraghm close to the top of the outlet tube. This reduces the amount of gases being drawn from the crankcase and decreases the vacuum level in the crankcase." The CDR uses vacuum to regulate the blowby in the crankcase at idle. It deals with the vapors that build up in the crankcase and uses a mild vacuum to evacuate that vapors to prevent the rear main seal from blowing out and letting your oil out. On the stock engine it uses ports on the intake to generate the vacuum needed for the system to work at idle the CDR is open and sucking crankcase blowby out as RPM increases so does vacuum and the CDR closes. On turbo engines the two inlets on the manifold are pressurized so you cap the intake ports and use the inlet or vacuum side of the turbo to generate the negative pressure needed to keep the CDR functioning properly. The CDR is essentially a PCV for diesels. The concern for these engines is at idle. Once they get up to operating speeds this is less of an issue.

The old advice was to change the CDR every 30,000 miles but they are getting harder to find and according to the thread I found here you can actually clean them (DO NOT USE SOLVENTS) with a long cotton gun swab / qtip or they can be uncrimped and carefully cleaned. There is a crossreference new part made by Delco (check the thread) that has the same function but it may not be exactly the same size inlet port as what is on your truck currently. Food for thought if you replace it with a new CDR you may have to make a longer hose. There are about 4 manufacturers of hose that will work and none of them sell in small quantities. Nor is the hose molded so depending on your setup you may either have to make the hose semi rigid (to avoid kinks) or use connectors if you have to navigate around things. In my case I haven't gotten around to heat wrapping the hot side of my turbo yet so I will be routing the vacuum side a little creatively and use thick aluminum foil to heat shield it.

The CDR deals with oil vapors and when that stuff condenses it can sludge the sealing surfaces of the valve. The way you test if your CDR needs replacement or cleaning is to setup an inches of water gauge using clear pvc tube routed to your dipstick or a magnehelic gauge (which is something so specialized you would have to be a mechanic or in an industry that uses them to really want to consider having one around) and you test the pressure difference at idle. I believe if its below 4" of water the CDR valve is working correctly. I'm going off memory because I don't feel like pulling the manual out.

I believe this is the cause of one of the leaks on my truck so getting that system back online is a priority.

From the GM 6.2 Technical Training Manual
PP 7-36 has a diagram showing different test points, the one dealing with the dipstick is the test in question.
PP 5-2 has theory and operation for the CDR valve
PP 5-3 show how the inches of water gauge works. Its really simple to make and test.
 
Last edited:
T

tom lovinggood

Member
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Location
Lees Summit, Missouri
Zen--I was not aware of any problems with my existing CDR valve, but it was very dirty and covered with soot. Rather than trying to clean it, I thought it might be best to replace it, as it appears to be a very easy swap.
 
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