how to detect a broken CDR-Valve?

[frauhansen]

Hello together

My rig starts burning oel, i think. Not dramatic but noticeable. I think 1 quart on 1k mils.
At the same time, I imagine that I am getting more black smoke from the exhaust when hitting the right pedal.
But my air filter is still clean. No oel on it.
My motor has only 10k miles on it.

Could that be the CRD Valve? Is it possible to test it for broken or not?

 

[juanprado]

My guess would be to put a vacuum gauge & pump on the small hose and see if it holds the low pressure when pumped up. If not, I would assume the diaphragm is broken.

 

[Retiredwarhorses]

Just replace if you are concerned, the CDR valve can also load up with oil if an engine has blow by…you want to replace the CDR valve anyway as part of maintenance.

 

[frauhansen]

Is the CDR changed frequently? As part of the maintenance schedule?

 

[Milcommoguy]

One quart in 1000 miles... I would think that is a LOT going up in smoke, out the tail pipe or on the ground.

10K miles on a new ??? engine is not even broke in, so maybe, but does seem excessive. I not sure one can believe any Humv odometer, unless one had the new engine and installed the meter at the same time while standing right there.... just saying. Then again there are the lucky ones. I have 52,000 miles which I believe ?? more or less ?? correct. My old 1987 M998, runs like a top and burns NO oil in 4K miles, No smoke, just goes and goes. So there's a sort of reference.

HumV thirsty for dinosaur fluid, CAMO

 

[AAVP7]

A few years ago, I noticed blowby coming out of the oil filler tube. I then did a measurement of crankcase over-/underpressure with the procedure shown in one of the TMs. Basically, you just plug a clear, flexible tube into the oil gauge tube, then form the clear tube into a U-shape, and fill the U with some water-based fluid (I used water with a bit of green coolant for better visilbility).

When you start the engine then, the water wil be displaced an inch or two either towards the engine (underpressure in crankcase), or away from the engine (overpressure). The difference in water levels can be checked against values in the TM.

In my case, if I remember correctly, I had overpressure in the crankcase even at idle, which is not good. This did not change even after I put in another CDR valve, so the culprit was not the CDR, but blowby-gasses at valves or piston rings.

This pressure test is a pretty simple but really helpful prcedure to get a feel what is going on in your engine.

 

[frauhansen]

The smoke from the exhaust is not something I find alarming. You only notice it if you drive directly behind it or consciously observe it in the mirror. A classic diesel. You can see when the driver accelerates.

Of course I can't check whether my engine had the 2kml on it when I picked it up. From the visual impression, however, it was put directly into the desert in Barstow after the overhaul in 2009.
Nevertheless, the oil consumption makes me a little suspicious. That's why I came across the CDR Valve. But that would burn the oil via the air filter. If everything is clean in there, it can't be the CDR valve? Or am I wrong?

 

[Retiredwarhorses]

A few years ago, I noticed blowby coming out of the oil filler tube. I then did a measurement of crankcase over-/underpressure with the procedure shown in one of the TMs. Basically, you just plug a clear, flexible tube into the oil gauge tube, then form the clear tube into a U-shape, and fill the U with some water-based fluid (I used water with a bit of green coolant for better visilbility).

When you start the engine then, the water wil be displaced an inch or two either towards the engine (underpressure in crankcase), or away from the engine (overpressure). The difference in water levels can be checked against values in the TM.

In my case, if I remember correctly, I had overpressure in the crankcase even at idle, which is not good. This did not change even after I put in another CDR valve, so the culprit was not the CDR, but blowby-gasses at valves or piston rings.

This pressure test is a pretty simple but really helpful prcedure to get a feel what is going on in your engine.

A CDR valve doesn’t create blow by….blow by is completely normal in all engines to some extent, it just depends on how bad.
I’ve had engine that appear to be quite severe and run absolutely perfect for many many years.

 

[AAVP7]

OK, understand, but as far as I thought, a defective CDR valve could cause wrong pressure inside the crankcase ?

 

[Mogman]

The smoke from the exhaust is not something I find alarming. You only notice it if you drive directly behind it or consciously observe it in the mirror. A classic diesel. You can see when the driver accelerates.

Of course I can't check whether my engine had the 2kml on it when I picked it up. From the visual impression, however, it was put directly into the desert in Barstow after the overhaul in 2009.
Nevertheless, the oil consumption makes me a little suspicious. That's why I came across the CDR Valve. But that would burn the oil via the air filter. If everything is clean in there, it can't be the CDR valve? Or am I wrong?

The CDR valve is plumbed directly into the intake so if there was excessive blow by you would not necessarily see oil in the air filter

 

[frauhansen]

But, can a broken CDR Valve be the cause of increased oil consumption?

 

[TOBASH]

But, can a broken CDR Valve be the cause of increased oil consumption?

Unlikely. CDR is like EGR and my understanding is that it directs blow by into the air intake for consumption in order to diminish pollution. It does not directly consume oil.

 

[frauhansen]

Now it's getting embarrassing... at least for me!
I had suspected that my CDR valve wasn't working correctly and that I might therefore have had increased oil consumption.
After I had lost sight of the issue, I went back to it yesterday.
I had ordered a new CDR valve with the car at the time. So more than 2 years ago.
I got it from the warehouse yesterday.

I've already done a hell of a lot of work on the truck. Even in the engine compartment. But what I never noticed was the CDR Valave.
Especially not because I didn't have one!

It was probably removed as part of the demilitarization and replaced with a hose. Which was simply plugged into each other.

I've now fitted the CDR valve... the new one... and I wonder how I could have been so blind for so long.

But I have two more questions.
If I read the above correctly then one indicator for a defective CDR valve was that oil collects in the air filter box. But the connection goes from the oil filler neck to the intake manifold. How on earth is the oil supposed to find its way from the intake manifold back into the air filter?

Furthermore, can the vacuum in the intake be so high without regulation (no CDR valve) that it explains the increased oil consumption? I need about 1 quart per 1000 miles. However, I have neither an oily exhaust nor a lot of smoke.

 

[Mogman]

Now it's getting embarrassing... at least for me!
I had suspected that my CDR valve wasn't working correctly and that I might therefore have had increased oil consumption.
After I had lost sight of the issue, I went back to it yesterday.
I had ordered a new CDR valve with the car at the time. So more than 2 years ago.
I got it from the warehouse yesterday.

I've already done a hell of a lot of work on the truck. Even in the engine compartment. But what I never noticed was the CDR Valave.
Especially not because I didn't have one!
View attachment 914998
It was probably removed as part of the demilitarization and replaced with a hose. Which was simply plugged into each other.

I've now fitted the CDR valve... the new one... and I wonder how I could have been so blind for so long.

But I have two more questions.
If I read the above correctly then one indicator for a defective CDR valve was that oil collects in the air filter box. But the connection goes from the oil filler neck to the intake manifold. How on earth is the oil supposed to find its way from the intake manifold back into the air filter?

Furthermore, can the vacuum in the intake be so high without regulation (no CDR valve) that it explains the increased oil consumption? I need about 1 quart per 1000 miles. However, I have neither an oily exhaust nor a lot of smoke.

I would suspect 1qt/1000mi is not excessive for a Melton engine. although not having a CDR valve certainly could cause an increase in oil consumption.