Valve adjustment - my experience
 

just finished the finale valve adjustment for the diesel 300DT. adjusted them a week ago but grabbed the wrong size feeler gauge for the intake valves. so, this AM fired it up and drove until the engine was good and hot. took the cam shaft cover off and then jacked the car up and put it on ramps. rotated the engine by placing a socket on the bolt on the bottom engine pulley. did the intakes first and then rechecked the clearances. two were not quite right, so readjusted. then, went back and checked the exhaust valves and four of them were off, so readjusted those.

just prior to this, I had installed new cap nuts on each valve stem. probably should replaced the locking nuts as well, but that will be another project. the car now has new valve stem seals, new valve springs, new cap nuts, new Monark injectors, new return lines and replaced nine cooling line hoses and a new mercedes OEM thermostat along with a new Nissens radiator. that is one killer radiator, btw. using amsoil diesel rated coolant in the system. car should be good for another 15,000 miles.

what I learned: these diesels are PRECISION engines and require precision minded maintenance. I'm purchasing a set of genuine mercedes feeler gauges for the next scheduled valve adjustment as I don't trust the made in china stuff.

Where did you get the idea that setting them hot was the most accurate way ?

When I was doing my first valve adjustment, I had a family friend tell me that I needed to adjust the valves with the engine hot. :confused: He's a farmer who does all of his own work on his truck and tractor. However I did it cold as per advice on this forum.

Generally, I don't take the advice of random people regarding my car. It's kind of funny how I trust the advice of a bunch of people on an internet forum that I have never meet over a real life person. :cool:

IF YOU ARE GONNA SET IT HOT
 

Don't even bother with PRECISION guages.....should be set stone cold.

Regards

since the engine runs at operating temperature, doesn't it make sense to set the valves while hot?

the car had a tap tap tap sound which started me on my quest for higher knowledge. with the new adjustment the knocking is GONE.

a mercedes mechanic with over 20 years experience at the dealership told me to do it HOT.

Answer
 

Correct adjustment is Always cold per WIS..

Cold is defined as engine ambient:

* -20 to +30 Celsius = -4 to +86 Fahrenheit.

Check your e-mail for further data FYI. :)

When I read adjustment specs that can be do Hot or Cold I figure I have a choice and do what is most easiest for me to do.

If I lived someplace where the temp was commonly in the 100-120 degree range I would consider adjusting the Valves Hot.

guess we will have to agree to disagree. the tap tap tap
knock knock knock sound coming between cylinders #2 and #3 was driving me crazy, now the engine sounds great, which is good enuf for me.

answer
 

you have a PM.

just checked my PM and didn't see anything.......

exactly, the car was experiencing an issue related to the adjustment, I consulted with an experienced factory trained mercedes mechanic and he suggested I adjust the valves hot. my dad is a certified diesel mechanic and he says do 'em hot. it appears opinions and the factory service manual may be in conflict....

I hear everybody has an opinion, and a rear end... both equal in my opinion to tuning a mercedes...:rolleyes:

Hmmm
 

:confused: sent again.

Quiet valves are tight valves. Some cars specs call for valves to be set hot. Some call for them to be set cold. Some give specs hot and cold. My 78Z calls for hot and gives a cold setting also. If the valves have been disturbed ie head R&R, I do a initial set at cold specs then warm the engine and set them hot. MBZ calls for cold & I don't think I can finish quick enough to set them accurately hot. Regardless hot or cold, I use a go/no-go gauge.

While I do not doubt that when MB dealers were doing a lot of these as routine service, they did them with the engine hot as a means of getting units in and out, the right way is cold...