LW4000 High Pressure (arch) issue

[bandali]

High Pressure in arch is really low (440 psi). Undercarriage is perfect (1100 psi).
Have already tried the following:

• rebuilt both lexair valves
• swapped lexairs, again undercarriage is fine, arch is low
• cleaned, then replaced Mac Valve
• cleaned all nozzles
• replaced weep check valve
• tightened belt

There is no leak, noise or pressure buildup anywhere.
We are able to wash cars, but obviously regular customers can tell the difference.

I've had this issue before, about 2 years ago, and one of the above steps fixed it.
Other posts seem to indicate that I should replace the lexair/macvalve setup with the dema.
That is my last resort, if I can't figure this out. If someone can share a pic of their final retrofit, that would be super awesome !

 

[chaz]

Had a similar issue on my markvii gt700. Replaced both unloaders

 

[pgrzes]

I would also say check the unloaders.

 

[UndertakerII]

I would say it's likely a bad check valve up on top where all the products for the arch combine. If the unloader was bad I would think that it would affect the undercarriage as well. Keep us posted as to what you find! Kevin

 

[OurTown]

Is it possible that the pump can't quite deliver the extra volume needed for the arch therefore not getting to pressure? We had a similar issue with our touchless a while back with the undercarriage working perfect and the arch not getting up to pressure. It turned out to be a kinked inlet suction hose between the gravity tank and pump. In talking to Cat pumps the guy said that our 1.5" ID hose was the minimum diameter so even the smallest issue in the hose would cause enough restriction in flow to starve the 3535. It had a regular polybraid vinyl hose on it which is of course not made for suction so we replaced it with a hose rated for suction and has been fine since.

 

[soonermajic]

I agree with Our Town. Go to a inlet 2" hose, instead of 1.5"

 

[Ontario Car Wash]

Does water come out of u.c. When its spraying from arch or vise versa

 

[bandali]

Thank you for the suggestions. Didn't think of unloader because as @UndertakerII noted, if the unloader was bad I assumed it would affect both the u/c and arch. There are 2 HP unloaders and iirc, one is for the clearcoat (800 psi).

@Ontario Car Wash - yes, when the arch is spraying (at 400psi), water DOES come out of the undercarriage !

So I have 2 other suggestions that I need to look into: bad check valve where the LP chemicals combine and using a 2" inlet suction hose.

Will try both these this weekend and report back.

 

[chaz]

I’d still suspect the unloader may be an issue. Are they pretty rusty looking as that will affect the spring tension. If the undercarriage is coming on full power with the rinse arch then the Appalo valve (assume U have one) likely is not fully operating...could just need cleaning.

 

[bandali]

When the arch is enabled, i'd say the water is 50/50 between the arch and undercarriage.
When the undercarriage is enabled, nothing comes out of the arch.

This is why I'm assuming the unloader is fine. No visible rust (I've cleaned rusty unloaders in my other locations).
All my LW4000 bays have 2 of these for the HP: https://www.kleen-ritecorp.com/p-17...pressure-regulator-valve-53-gpm-2900-psi.aspx

 

[chaz]

My markVii has an air controlled valve that switches between UC and Arch. If you have a similar valve, the issue is likely in that valve or control

 

[bandali]

Yep, the LW uses this: https://www.kleen-ritecorp.com/p-46...oid-valve-for-laser-wash-912b-pm-221caab.aspx
As noted, I already replaced this (first tried cleaning it, then just replaced it).

 

[dreese]

Thank you for the suggestions. Didn't think of unloader because as @UndertakerII noted, if the unloader was bad I assumed it would affect both the u/c and arch. There are 2 HP unloaders and iirc, one is for the clearcoat (800 psi).

@Ontario Car Wash - yes, when the arch is spraying (at 400psi), water DOES come out of the undercarriage !

So I have 2 other suggestions that I need to look into: bad check valve where the LP chemicals combine and using a 2" inlet suction hose.

Will try both these this weekend and report back.

IMHO, doubt it's an undersized feed hose. If the pump was being starved it would starve during undercarriage operation as well as at the arch. Slight chance of the check valve in the holding tank intermittiently sticking,but this is a stretch.

Same reasoning with the unloaders. If you have 2 unloaders on the HP line, you have water saver (HP solenoid that opens to bypass water during chem passes if programmed). Could have an issue with this valve not closing fully, but you should notice pressure problems / cavitation during all HP functions.

However, if you are seeing water thru the undercarriage as well as the arch during all HP passes you're getting bleed thru at the LexAir valve - the undercarriage side is not closing fully. Either the rebuild kit didn't take, the body (seat) of the valve is bad allowing water to bypass, the Mac (blue changeover) valve is bad and not supplying enough air to hold the Lexair closed, or air pressure to the Mac valve is low (needs to be around 100psi). Cycle the y20 output using the diagnostic menu, listen if you are getting a solid changeover thru the Mac valve - you should hear a solid air exhaust as the valve cycles. The diffuser - the brass piece on the bottom of the valve - could be plugged.

 

[Eugene]

This is not rocket science . If water is coming out of arch and undercarriage at the same time the HP water is blowing open the lexair valve on the right . Bad valve or lower air pressure . Air on lexair valve should be 10% of high pressure . Switch air line on lexair valves see what happens then you have your Ans . Its a push lock fitting easy to switch . If you switch air lines then only the arch will spray. You can run like that you just will have no undercarriage till you fix the valve are air pressure on the right valve .

 

[bandali]

Update - as suggested, I checked the HP check valve on the manifold, and the hose for kinks - all checked out fine.

Next, I connected the air line directly to the RHS lexair (undercarriage), thereby bypassing the mac valve and forcing the u/c to stay closed.
Same problem. Sounds like what Eugene said - bad rebuild kit or low air.

I used another rebuild kit AND changed the air regulator (I'm fed up of guessing). It worked! No water coming out of u/c.
So, re-attached the mac valve and ran it as normal. Same problem!.

Repeated the steps again (yes, used another rebuild kit) and bypassed mac valve, connected air line directly to RHS lexair. Same problem!.

So I took the lexair apart and started looking inside the (brass) body of the lexair. Looks like it's beginning to wear out (see pics). I've never seen this before. Could this be the cause of my issue?

View attachment 1201 View attachment 1202

 

[Ontario Car Wash]

Your lex air valve is not working
if water is coming from uc when arch should be on or vice versa
if water coming from arch when uc is on the lex air on left is bad
if water coming from uc when arch is on the lex air on right is not closing all the way
try to rebuild but not really worth it sometimes it works probalbly not
u could see if its something in there floating around but chance are its washed out
its easy to pop off and flush
i swithed both mine to demas
pm if you need
i went thru this last year

 

[pgrzes]

Those lex air valves do wear out in time. They are passing a ton of water and cavitation through them. Also try to turn off your pumps circuit breaker and switch your mac valve off and on for each the uc and arch and check that you are getting air through each proper air line. Sounds at this point though your lex air is bad?

 

[bandali]

UPDATE - it was indeed the brass body of the Lexair that was worn out. Found a new one on Ebay ($100), swapped it out (took about 2hrs since some of the plumbing was rock solid). Back in business.
I wanted to replace the Lexair with Dema but couldn't figure out how to wire it and get rid of the Mac valve.
If someone can DM me a pic or instructions, that would really help - thanks in advance !