Caterpiller IAPV Disassembly and Cleaning UPDATE
This might belong in Tech but since most of these engines are in motorhomes, I posted it here. If the moderators feel it should be moved, feel free....
I have a Cat 3126B in my '98 Ultrasport. Recently, I had my 4th IAPV failure in 145,000 miles. While one lasted about 80,000, most have failed at around 30,000 miles. I was talking to a gentleman at a diesel facility recently and he said he had disassembled them and cleaned them so I thought I would give it a try. Below is a picture of the disassembled valve. When I pulled it apart, the piston (the part closest to the valve body on the right) was not free in the valve. After cleaning, it is loose and freely slides back and forth.
By the way, I have done two of them now and one had a coil resistance of 12.3 ohms while the other was 10.8. I suspect that may be the tolerance in the coils as both seem to work fine in testing the valves on the bench.
The disassembly was a bit of a challenge as it appears that they used some type of locking compound to hold the parts together. Having nothing to lose, after using a punch to mark the relative position of the parts, I used a pair of vice grips and was able to unscrew the assembly. I carefully counted the number of turns to remove the end. It took just under 9 turns. The vice grips left almost no marks so I don't believe any damage was done.
After carefully cleaning the parts in my parts washer, I followed up with a cleaning of spray carburetor cleaner and then used light oil (3 in 1) to lube everything before reassembly.
Note the TINY valve in the left of the picture. That fits inside the protrusion on the threaded part on the left. Also, the "pin" that is below the part in the center with the threaded end, fits inside that part. It was also "sticky" when I took it apart and after cleaning would literally fall through the threaded part.
I used blue Loctite on reassembly and tested the valves with a power supply. After cleaning, I mounted the valve in a vice with the solenoid below the valve. When applying voltage (I used 6 volts from my bench supply) you could clearly hear the piston click as it moved up in the valve.
I have not put one of my cleaned IAPV's back in the motor yet but plan to do that in the next few days and will report on the results. At almost $200.00 for a new one from Cat or $100.00+ for a Chinese copy (may be better than the cat valve!), I hope the cleaning works. If it does, I think I will just pull and clean every 25,000 miles or so.
Hope this helps someone else.
Steve
Some have asked where the IAPV is located. Here's a picture of what it looks like. The part on the left is what screws into the HUEI pump so what you see when it is installed is from the large hex to the right. The solenoid is removed by removing the small nut on the right. When that's removed, a spacer and the solenoid coil slide right off the valve. The two wire connector is on top of the coil.
In the case of my engine, the coil will not come off the valve when it's installed (hits a nut for an oil line) but I can remove the nut and spacer from valve and then remove the valve from the pump and then slide the whole assembly out.
I have a Cat 3126B in my '98 Ultrasport. Recently, I had my 4th IAPV failure in 145,000 miles. While one lasted about 80,000, most have failed at around 30,000 miles. I was talking to a gentleman at a diesel facility recently and he said he had disassembled them and cleaned them so I thought I would give it a try. Below is a picture of the disassembled valve. When I pulled it apart, the piston (the part closest to the valve body on the right) was not free in the valve. After cleaning, it is loose and freely slides back and forth.
By the way, I have done two of them now and one had a coil resistance of 12.3 ohms while the other was 10.8. I suspect that may be the tolerance in the coils as both seem to work fine in testing the valves on the bench.
The disassembly was a bit of a challenge as it appears that they used some type of locking compound to hold the parts together. Having nothing to lose, after using a punch to mark the relative position of the parts, I used a pair of vice grips and was able to unscrew the assembly. I carefully counted the number of turns to remove the end. It took just under 9 turns. The vice grips left almost no marks so I don't believe any damage was done.
After carefully cleaning the parts in my parts washer, I followed up with a cleaning of spray carburetor cleaner and then used light oil (3 in 1) to lube everything before reassembly.
Note the TINY valve in the left of the picture. That fits inside the protrusion on the threaded part on the left. Also, the "pin" that is below the part in the center with the threaded end, fits inside that part. It was also "sticky" when I took it apart and after cleaning would literally fall through the threaded part.
I used blue Loctite on reassembly and tested the valves with a power supply. After cleaning, I mounted the valve in a vice with the solenoid below the valve. When applying voltage (I used 6 volts from my bench supply) you could clearly hear the piston click as it moved up in the valve.
I have not put one of my cleaned IAPV's back in the motor yet but plan to do that in the next few days and will report on the results. At almost $200.00 for a new one from Cat or $100.00+ for a Chinese copy (may be better than the cat valve!), I hope the cleaning works. If it does, I think I will just pull and clean every 25,000 miles or so.
Hope this helps someone else.
Steve
Some have asked where the IAPV is located. Here's a picture of what it looks like. The part on the left is what screws into the HUEI pump so what you see when it is installed is from the large hex to the right. The solenoid is removed by removing the small nut on the right. When that's removed, a spacer and the solenoid coil slide right off the valve. The two wire connector is on top of the coil.
In the case of my engine, the coil will not come off the valve when it's installed (hits a nut for an oil line) but I can remove the nut and spacer from valve and then remove the valve from the pump and then slide the whole assembly out.
