Tow point Cat AP655C

[Mike456]

Been having issue with my tow points. Can’t seem to get them to work. I have power going to them, and hydraulic fluid as well. But I know it’s not enough hydraulic pressure to operate them. Everything else works on it. Including the hopper, which those and the tow point run to the same hydraulic manifold. I’ve tried just about everything. I’m lost on this

 

[ahart]

Throw out a serial number and we will see what advice we can offer.

 

[Mike456]

Throw out a serial number and we will see what advice we can offer.

S/N C6E22791

Thanks for the help. Me and my fellow Seabees would greatly appreciate any advice or help

 

[ahart]

GNZ00333 is the serial number of the machine based on the serial number you provided which is the engine serial number. Have you teed gauges into the cylinder ports and ran the controls for the tow point cylinders? The counterbalance valves keep the pressure at 1900 psi when the solenoids are activated. There is a pressure tap on the control manifold that can be used to measure the supply pressure to the valve coming from the auxiliary pump, one on each valve for left and right. First thing I’d do is get gauges on it and see what numbers we are actually seeing.

 

[Mike456]

Sorry about S/N. It’s a military piece of equipment, so everything is painted over. But we’ve put a gauges on it, the only place pressure is low are at the tow points, even at control manifold for the tow point/ hoppers. What confusing to me, the hopper works fine..

 

[heymccall]

 

[ahart]

What is the pressure at the control manifold test port?

 

[heymccall]

Some more snippets from here...

AP655D and BG655D Asphalt Pavers Machine Systems Caterpillar

avsmanual.com

 

[Mike456]

What is the pressure at the control manifold test port?

It was a 100 psi

 

[ahart]

Do this test and report back findings.

 

[Mike456]

Ahart, thank you for the info and response. We completed the test, the aux pump is putting out the pressure is should. We’re only get 100 psi still to tow points. I’m thinking it’s the pressure reducing valve but what gets me, and something I’ve never seen is that both valves fail at the same time…

 

[Mike456]

It^

 

[Mike456]

Do this test and report back findings.

Ahart, thank you for the info and response. We completed the test, the aux pump is putting out the pressure it should. We’re only get 100 psi still to tow points. I’m thinking it’s the pressure reducing valve but what gets me, and something I’ve never seen is that both valves fail at the same time

 

[heymccall]

 

[ahart]

One thing you might check, does the hopper quit if you try to run the tow point at the same time? Since both valves use aux pump pressure for supply, either PRV being bad might dump pressure for both. I’d have to look at the schematic again to verify this is how it functions.

 

[Mike456]

One thing you might check, does the hopper quit if you try to run the tow point at the same time? Since both valves use aux pump pressure for supply, either PRV being bad might dump pressure for both. I’d have to look at the schematic again to verify this is how it functions.

I’ll give that a try. One thing I did was swap lines from tow point to the hopper. And the tow points worked perfectly and hopper didn’t work..

 

[heymccall]

 

[Mike456]

Hey fellas! I figured it out a coupl weeks ago, sorry for the delayed response. The issue were the o-rings inside the pressure reducing valves for the tow point on both hydraulic manifolds, who would have thought!!! We pulled them apart, and that little oring, just crumbled. It was pretty bad!! Thank you all for the advice and help!!