Valve lifter noise in Motorhome

[George Schweikle]

I'm a multi year Diesel Page subsciber, but just joined the forum. I have a 1995 Safari Trek motorhome, 26 ft. Milaege is 111,000, and the injection pump was replaced under warranty a few years ago. I usually travel with an open race car trailer.

In the last year, what sounds like hydraulic valve lifter noise has been occuring ("tapping"). Usually after a downshift from overdrive, and under a hard load. I can eliminate the noise by easing the gas pedal, but the basic condition appears to be getting worse. The resolution is probably just to replace the lifters, but I'm interested if any other forum members have experienced this condition.

Thanks,

[DmaxMaverick]

Welcome to the Forums, George!

Your description sounds more like a fuel knock. A lifter isn't nearly as load dependent, like a fuel delivery event, and will generally sound off at a specific RPM regardless of load. At 12 years and 111K, the injectors are suspect. A noisey lifter should also make some noise at idle (oil pressure lowest) and most noisey at a cold start.

[George Schweikle]

DmaxMaverick,

Thanks for your reply, I will use the search function to browse for "fuel knock" information. And, it sounds like a trip to the dealer is in order for some diagnosis.


Welcome to the Forums, George!

Your description sounds more like a fuel knock. A lifter isn't nearly as load dependent, like a fuel delivery event, and will generally sound off at a specific RPM regardless of load. At 12 years and 111K, the injectors are suspect. A noisey lifter should also make some noise at idle (oil pressure lowest) and most noisey at a cold start.

[DmaxMaverick]

If you can turn a wrench, save yourself a trip to the dealer. Injectors are pretty simple to diagnose.

If you can make it sound off with the engine running while sitting still, it's easy. If it's under load only, it's a little more difficult, but not too bad. If it knocks while idling, even a little knock, loosen one injector line nut at a time. If you have a leaky/worn injector, the noise will go away as soon as the line is loosened. The engine will miss, but the knock will disappear. If it only happens under load, you will need help to duplicate the conditions while stationary.

[JohnC]

If it only does it under load you can use the "Cylinder Balance" test on the Tech II to do the same thing (Shut the injectors off one at a time).

[George Schweikle]

Hi JohnC,

I couldn't find "Tech II" searching the forum, but found one for sale at $2995.00 on the Internet. Kinda sounds like a Dealership of Diesel shop item, and I would visit such an establishment If I want a diagnosis.

My inpression from responses to this thread is that I don't have hydraulic lifter noise, since it doesn't occur at idle or low engine speed, and the problem is likely injector(s). I drove the motorhome yesterday to freshen my memory of the condition. I ran up a long relatively steep Interstate hill at full throttle in 3rd gear, and the noise was just barely there after cresting the top (ambient temperature 37F). This compares to a month ago on a steeper hill, not quite full throttle in 2nd gear. The clatter ocurred fairly quickly and was loud (temp 55F). Assuming the injectors need replacing anyway at 111K miles, I wonder if I should use stock or "High performance" injectors?. The engine is stock, and the only upgrades planned are a better exhaust system and maybe a mild chip. BTW, the motorhome weighs 14,460 lb., and the car trailer is 4,480 (18,940 total).

Thanks to all for the information and advice. I will verify there isn't anything simple like an injector line vibrating against something, and will probably change injectors before the next long trip (also ordered the Diesel Page 6.5 Turbo book to go with my 6.5 troubleshooting guide).


If it only does it under load you can use the "Cylinder Balance" test on the Tech II to do the same thing (Shut the injectors off one at a time).