Valve adjustment frequency problems

[dpuckett]

I am having to adjust my valves every 12-15K lately. They will be out of spec by 2-5 thousandths. I have been adjusting them to . 009" and . 019" as per recommendation of Scott and a few others. Could this be leading to the frequent adjustments being necessary? What could be the problem? Cam or lifter wear? Has anyone else had this problem/ issue?



ADjustments have been on a stone cold engine (overnight sitting), and I have been turning the engine at the crank (alt belt slips) to TDC with the timing pin, then following FSM instructions from there. TIming pin has been checked to be dead on. My MPGs will be fine for a while, then start to slowly go down to about 15 city (normal is 18), then I will check fuel pressure, boost, EGTs, etc, with the valves being a last resort after checking everything else.



One more note- my other 91 (91. 5), bgilbert's 90 donor, and my mom's 92 all have the wide-set numbers on the odometer. My 11/90 has the narrow set numbers like a 93, which leads me to believe in the possibility of the speedometer having been swapped out sometime up the line, so actual mileage could be hard to actually verify. i know oil analysis could point to possible cam wear, and we all know what would go in there as a replacement cam... .



Thanks in advance- all ideas appreciated,

Daniel

 

[Jet Tech]

Have the valves been found too tight? (to little clearance, indicative of a valve or seat problem) Or too loose? (too much clearance, indicative of a valve train or cam problem) Also, is it common to all valves or is the trend towards certain cylinders?

 

[bgilbert]

You probly already read this before, so it might not be any help. But from the T&R manual:

Excessive valve lash can indicate a worn valve stem, push tube, valve tappet, or rocker lever.

Loose rocker levers and the need to reset the valve clearance frequently can also indicate camshaft lobe or tappet wear. If an inspection of the rocker levers, valve stems, and push tubes does not show wear, then tappet, and/or camshaft lobe wear can be suspected.



I'd say time to spend the $20 for an oil analysis and see if anything out of the norm shows up.

 

[BushWakr - RIP]

One other item I don't see mentioned yet... . In the shop we'd set the valves when the engine/valve-train was between 90*F - 100*F.

Normally you don't see that much of a variable in valve sets... on my truck for example, I have gone as much 35K - 45K between 'sets' and even then the amount of adjustment was only a couple 'thou at most...



Go with some of the guys thoughts on pushrods/valve stems etc but first reset the engine when it is just warm to the touch.

Also you use alternator nut to turn the engine over by turning it counter clockwise... if the belt slips going that direction then it needs setting too. . or look for excess wear perhaps. .



pb... .

 

[JLEONARD]

My opinion is that if you are having to adjust that often due to camshaft or tappet wear, then the mileage in between adjustment will decrease rapidly... very rapidly.

I would say that you should get the oil analysis done as Bill suggested and see if iron is high.

Heck if it's wearing that fast you should see iron particles on your oil plug I would think.

Jay

 

[dpuckett]

Jay, I was thinking the same thing. I will see about getting a kit in teh next month or so and see what happens. ANyone know where to get an oil analysis done? I might try local places, but wont hold my breath waiting on anything.



Pastor Bob- I have tried setting the valves on a warm engine. Problem is, I take so long to get it just right, that by the time I get done with Part B, the engine has cooled to room temperature. Maybe if I plug it in next time and leave the block heater attached? I tired turning it with the belt- it'll go a little way til a cylinder builds compression, then it slips. 17mo old Dayco tensioner, Gates belt.



Jet Tech- They have always been loose- more so in the middle, and more on the intake side than the exhaust. The exhausts will usually be within a thousandth or two of each other, but still loose. Intakes will vary as much as . 003-. 004" Might do an early oil change just to satisfy my curiosity. If I get a new cam, it will no longer be for sale



Daniel

 

[MMiller]

Do you beat on the rockers, push rod side, with a rubber hammer before adjusting the lash? Cat engines, and I believe the cummins tells you to do this, to make sure everything is "bottomed" out in the lifter, cam, rocker. I think I have adjusted my valves 3 times in 222,000 miles, and have never noticed any changes in fuel economy. Usually mine don't change much at all?



I agree with Jet tech, that you are gaining on the cam/lifter/rocker side of things, cause your adjustment is getting loose.



Caterpilliar dealers usually have an SOS(oil sample service). I know we charge $11 for an oil anyasis. Just waltz into your nearest Cat dealer and ask.



Michael

 

[RBergman]

this is who we use(at work)

http://www.oillab.com/

 

[dpuckett]

Michael-

No, I havent beat on the rockers with a rubber hammer, but I do apply a goodly deal of downward force (as much as my one arm can do without sweating profusely) as I slide the feeler through the gap. I know, the sharp blow from a rubber hammer woudl shock stuf down deeper than a steady pressure, but it is more than some shops do.



Thanks for all the replies, guys.

-DP