Constantly Failing Diesel Vacuum Pumps

Look for the cause in the drive mechanism

Vacuum pump drive failure is becoming more of a problem as these old diesel 616 and 617 engines age. Both pump pistons and cover plates are failing and often when a pump is changed the same thing will happen to the replacement pump in a short order.. This can also cause pre-mature failure of the rubber diaphragm on early models and the piston on later models.

Scroll down to learn what to check if you find yourself faced with this problem:

Problem & Solution

Common among these chassis:


1. Check the pump drive bearing and pump lever assembly.  Look for signs of adverse wear in the pivot points and on the bearing.

2. Check the springs inside the pump. You should have to push VERY hard to compressed those springs. If you can push the springs in easily the pump mechanism can "jump" putting extra strain on the rubber diaphragm causing it to tear.

3. Check the timing device bushing and cam.  (See second picture). The shaft that drives both the timing device and the injection pump is supported in a bronze bushing. If this bushing should wear excessively the shaft can wobble thus changing the alignment of the vacuum pump drive cam to the pump bearing. Although bushing failure is rare, its condition should be checked when you are experiencing repeated vacuum pump problems. To check for side play it's best to remove the timing chain tensioner first. Then grab ahold of the timing device and pump cam and try to move it side to side. If it moves more than 3/32 of an inch at the end of the nut then you may have a problem. Do not ignore this bushing. If worn and ignored it could cause excessive timing chain wear leading to timing chain failure... and we all know that destroys an engine!

4. Make sure your timing chain is not worn out. If loose it can cause the timing device to "rattle" stressing the pump.

NOTE: If you see signs your pump is worn out you should look for another good used pump as they are not available new any longer.