Valve adjustment

[Dan Murphy]

Jerry
I paid $355 at a Cat shop in Indiana last June.I did no prep work.

[Jerry Emert]

Thanks Dan, I appreciate your info.
Jerry

[Doug Till]

I really appreciate all the input on this forum concerning the valve lash adjustment/inspection. It has been very informative.

I took my 2003 Marquis-Ruby into a Cat dealer to get the valve lash checked on the C12, 505 HP engine since I just rolled over 60,000 miles. The bed is a streetside to curbside. When I called the Cat dealer to get an estimate and schedule the work, he quoted 4 hours to do the work. Now, the dealer is saying a support is in the way to remove the valve cover and if I remove everything out of the closet it still may take 8 to 16 hours to do this work. Has anyone run into this issue? I dropped off the coach at the nearest Cat dealer which is still over 100 miles from where I am staying. I thought I would do some research before I make the trip back to the Cat dealer. Does anyone with this model of coach run into this issue? Thanks the advice.

[LaMonte Monnell]

I don't see how this could take 8-16 hours to do a valve lash inspection and adjustment.

Mine was about $300 at CAT in Brooksville, Fl a couple of years ago.

[William Jordan]

I just looked at my 03 ruby and with the c12 having 3 valve covers, The front is accessed from the bedroom hatch  Very easy! the rear from the rear engine access very doable ... however the middle has 1" (OR LESS) clearance to a aprox 3" wide steel support (under the closet wall) that runs the width of the coach. I see no way the covers coming off  unless when unbolted you could just slide the cover off almost sideways. I assume the valve assy sticks up some. 115 grand on mine and with that i assume no adj has been done. I dont see how it could be done short of dropping the engine. or cutting that support and the wood 2x above it!!!  So, Dave , whats the Risk in not doing it?

[Marty and Suzie Schenck]

Setting the valve lash on a C-12 in a Marquis or a Thunder is no easy task. The center valve cover has a brace right over the center head. There is a recommended procedure for a mode that I did on mine and saved a lot of money in labor costs. I have tried to post it on the forum but it won't take. If someone can post it send me an e-mail and I will e-mail it back. You could also do a C-12 valve adjustment search. I think someone else posted it for me about 2 years ago. Marty

[Edward Buker]

If you are getting the valves adjusted on your C12, there are also some Jake brake durability improvements that Cat has modifications for, that can be incorporated during the valve adjustments. Some of the later C12s have these built in, they will know by SN if you have these. I understand that these part changes are not expensive.

Later Ed

[Dave Atherton]

William Jordan, Valve lash is not necessary if the measurement of the valve lash is in acceptable
range. Check the valve lash while engine is stopped. Note: the Correct valve lash setting for
C-12 engine. (  Intake Valves 0.015 +, - 0.003 ), ( Exhaust Valves 0.025 =,- 0.003 ) what
this is telling you ( there is 0.006 gap  if feeler gauge will slide for adjustment, no adjustment is
necessary ).  There has been many thoughts  on correct setting of valve lash that been passed
around that is incorrect. Correct for lock nut torque if valve lash adjuster is moved is 22 +, -
foot lbs.  Looking at your milage and removing valve cover checking adjustments more than
likely adjustment will not be necessary as per above info. with valve adjustments taking into
Cat specs the plus and minus measurement of intake and exhaust valves. Again there has been
many different thoughts on correct valve adjustment and again cat specs has not change from
above, Dave Atherton Retired Cat Mechanic

[William Jordan]

Thanks Dave .  At the company I work for, the tractor mechanics also felt I needed to do nothing . Since the initial check is to make sure its retained its proper setting, and with 115,000+ on the odo and no problems I'll assume it was right at assembly.  .. I'll worry about it when it hits 300,000 ;-)

[Gerald Farris]

Roy,
There is a modification that is posted on the forum that some coaches need for access to the center valve cover.

Gerald