Intermittent Turbo Failure

[winemaker]

My turbo boost is failing on me and getting worse, but the symptoms seem bizarre. Here's my observations as to what has happened over the past week or 2:

1st oddity: I'm driving up a bridge with a load on, running the revs towards 3000 when the boost gauge suddenly falls off to 0 and power is noticeably less. I pull the next gear and all is well.

This same thing happens a couple more times over hte next few days.

Friday evening I start a 450km trip and stop for fuel about an hour in. When I get back on the highway, I have no boost and low power, and if step on the accelerator just more than the available power, it pukes black smoke.

The whole trip, best I can manage is 2 lbs boost, but not under load, only if I sneak up on it.

Next morning (saturday) when the truck is cold, no problem until same scenario as 1st oddity: running up toward 3000 rpm. Only 20 minutes of driving Saturday.

Sunday morning, start for home. I dare not accelerate rapidly toward 3000 because I sure would like to have boost for the next 6 hours. Drive her pretty tame and achieve as much as 10lbs once and 8 lbs a couple times. Comes time to pass someone on a hill, boost falls off like a brick and little power.

Drove like that for an hour, then stopped and turned the nut on my TurboMaster a good inch. Makes no difference, maybe even worsens slightly.

Monday morning (today) cold truck runs fine until I (for science's sake, of course) stand on it. Repeat of 1st oddity. Get off the throttle, then back on and I have boost.

So in a nut shell:
-I have a mechanical boost control so it can't be electronic issue, can it?

-it seems way worse hot than cold or normal operating temp

-tightening tension on the turbomaster didn't help

-can't be the turbo (can it) dropping off from 10 lbs suddenly would (I think) be catastophic, wouldn't it?
Any thoughts would be appreciated! Thanks folks.
Brett

[twaddle]

Check your hoses and clamps, maybe also look for any pieces of gasket sticking out on any flange sealing areas of the intake manifold. It sound like there may a leaking area that is sealing or just holding enough to let you see the 10psi then when the pressure reaches 10psi starts leaking down the pressure until the pressure is too low.
Let us know how you get on and good luck.

Jim

[rustyk]

I had exactly the same issue, and I eventually (after the second, less dramatic incident) discovered that it was a plugged air filter.

This causes the rubber L-shaped hose to collapse, as the turbo tries to suck air, and can't.

Change the air filter.

Note that the collapse will suck out a lot of engine oil, so check your level.

[winemaker]

You know I seem to remember you posting this issue a couple years ago. Funny thing is I was going to replace the air filter before this trip but time snuck up on me. I'll give that a try tomorrow. Thanks, and I'll keep you posted.
Brett

[winemaker]

Yup. Badly clogged air filter. I replaced it in the lot of the parts store this morning. The filter was so full of dust, it was like shaking the sawdust out of my shopvac filter!

Fired 'er up and drove to a small highway nearby. Stood on the throttle and she pulled 10lbs as long as I wanted. Not 100% conclusive having only driven for 5 or 6 minutes, but I'm willing to bet it's solved. Thanks Again!
Brett

[rustyk]

I think you're good to go - don't forget to check the engine oil.

BTW, a filter that's starting to plug may give clues; on mine, EGT will run 50-75°F high for the usual cruising boost. This may not work on a lighter vehicle (mine's usually at 15.5K lbs, and has around 100 sq.ft. of frontal area.

[Robyn]

Its amazing how a little plugged air filter will cause such trouble.

The stock filters dont give a lot of room for error.

If you like gauges you can easily plumb in a filter gauge.

These are available in a few types that can range from indicating inches of water column. 1_____________________ 30 etc with about 5 inches being time to replace the filter

My Big rig has this type.

The others can have a green yellow and red zone

Easy to hook up, just drill and tap a fitting in to the turbo side of the air pipeing .


Glad you got it scoped out.

Robyn