Cat 3535 sudden loss of pressure?

[GoBuckeyes]

Last week I had a Cat 3535 lose around 200-225 psi overnight on a LW 4000. Pump runs smooth, no visible leaks between pump and bay. Same max pressure whether its undercarriage or spray arm. Changed psi gauge to no avail. Lex-air valves appear to hold as there is no water coming out of opposite function. I took return hose off that runs from main regulator and watersaver loop back to pump inlet and not a drop being by-passed? Worn tips are a gradual loss, not a sudden loss. We figured it had to be the HP seals. Pulled head on Friday and replaced all the seals. We did find two that looked messed up and thought we were home free. Put everything back together and fired it up only to have the exact same max pressure, 800 psi! What gives?

I did have someone today tell me they had a similar incident and it turned out ot be the checkvalves even though the pump wasn't pulsing and ran smooth. I guess it doesn't cost me anything to pull those and check them. Any other suggestions?

 

[DiamondWash]

Could belt tension be affecting this?

 

[tdlconceptsllc]

Honestly most of the time when I have seen this in my personal experience its the belts not tight like Steve said above or the actual valves in the head on the pump like one of the plastic baskets is cracked or a spring is stuck open and not opening or closing you just need a big open end wrench and a strong set of needle nose I could tell you what size exactly tomorow when I go to my wash. Drain the water out holding tank so you don't get soaked and take each valve and plastic basket out they sell the baskets separately a fellow told me one day its more common on the big cats vs a 310 don't know why but I have done this on my laser 4000 before not hard and you will know instantly and eliminate them

 

[GoBuckeyes]

In the past I’ve used a big pipe wrench to take the check valve covers off. I’d like to buy a socket if I knew exactly what size they are. Anyone know?

 

[tdlconceptsllc]

I will look first thing in the morning bc I still have the big wrench I bought years back just for this from Napa

 

[MEP001]

It's 41mm. IIRC a 1-5/8" socket will work as long as it's not a 12-point.

 

[GoBuckeyes]

Thanks MEP! Although the only way I’d get those off with a socket wouldn’t be with a cheater bar. I had to use my 24” pipe wrench.

And out of the 6 checkvalves, 4 had either bad low pressure, high pressure or both seals bad. No broken springs or poppets which I guess is why it was smooth and not a pulsating loss of psi. Replaced those 4 and instant gain of 200 psi.

Thanks guys!

 

[MEP001]

When I used to service them I kept a 3/4" drive socket, 30" breaker bar and 3' piece of pipe for loosening them. The first time is always the worst since they put Loctite on the threads at the factory. I'd use an adapter for a 1/2" drive ratchet to finish removing the caps since they come out tight all the way.