Pressure drop, then repair, then vibration

[Sequoia]

My middle bay was ever-so-slowly dropping in pressure, and it got to the point where opening the regulator valve to full only allowed (tops) about 800psi. The hoses, boom, and wand were also vibrating although I couldn't pinpoint the source.

I successfully replaced the regulator valve and I was able to up the pressure a bunch-- back to normal of about 1,000 psi. The vibration almost completely went away, with just a trace/hint of residual vibration.

Now, a week later, the vibration has increased a lot, the pressure has dropped a little, and I don't know why. The boom, hose, and wand all vibrate and pulsate but the motor and pump don't seem to be abnormal at all. And, the water coming out pulsates a bit as well.

I know this is going to result in a failure soon-- anyone have an idea of where I should start hunting to identify the trouble?

Thanks!

 

[I.B. Washincars]

If the pump is sucking air on the inlet side it will cavitate and cause vibration. If you have eliminated air leaks you probably need to start looking at the pump. You need to pull the valves out of the pump and check for debris, broken disc, or a broken o-ring. If the o-ring is broken check the mating surface in the manifold to see if there is a matching groove in the casting. The manifold is pretty much junk IMO if it is grooved (washed out). If you don't find anything there it's time to pull the manifold and check the seals. Usually it's fairly obvious if a seal is leaking bad enough to cause a pulsation. Also check the manifold in the seal area for washout. If it is washed out, throw the pump away and order an Arimitsu from Randy.

BTW, if the pump is a Cat 310 you will need a special tool to remove the HP seal holder.

 

[JMMUSTANG]

I have the same problem on 2 pumps. Took apart the 310 pump apart 3 times and replced everything. Fixed one problem created another.
My CAT 623 is one of last original pumps. Decided enough was enough.
Just ordered a new CAT 310 and 623. Ouch.

 

[MEP001]

BTW, if the pump is a Cat 310 you will need a special tool to remove the HP seal holder.

I've found that a flat "wonder bar" prybar works better than the special tool for removing seal retainers. I bought the expensive socket which wore out after about a half-dozen uses and still rounded off a few retainers, but I've never damaged one with the wonder bar.

 

[ratfink102]

It sounds like your supply water is pluged up. Not getting enough water will cause hoses and pressure to pulsate.

 

[JustClean]

Hi all
First of all thank you guys for such a great forum. I have been lurking in the background for years. After doing a lot of research locally and of course on this forum here I finally opened my own wash. So far so good.
This might be the time to give something back to the forum community:

I had the same problem some weeks ago. Dealer, manufacturer, nobody knew what to do. I finally found out that it was the check valve between the hot water tank and the manifold that was sometimes not opening. As ratfink102 pointed out not getting enough water. I replaced all my Mark7 check valves. The original ones have a cone that can get stuck. I am using now flat ones and haven't had a problem since. I don't know it might not be the problem but I guess it's worth looking at it.
All the best
JustClean

 

[Sequoia]

Resolution

Just fyi the problem turned out to be some bad check valves in the pump head. This fixed 90% of the pulsation and low pressure, and installing a new tip in the wand too care of the other 10%.

 

[whitescout]

How worn was your tip??? It still sounds to me like either sucking air on the inlet side of the pump. ( If you are gravity fed, you can suck air without leaking water BTW ) Or, you are starving the pump. If you are gravity fed, please check for restrictions on the inlet side.( check valve ) Does the hammering or shaking occurr In all functions??? If it is happening on wax or soap only, you could be sucking air there.

 

[Sequoia]

Air

The tip wasn't excessively worn, but it was time for replacement of all tips anyway. I always replace tips and brushes in the Spring before the busy season.

During the repair, I tightened the connections on all supply lines leading to the pump, so I could have possibly fixed an air leak without knowing it. But, upon inspection, there were several check valves that were definitely bad.