What does your turbo sound like when it spools?
 

I ask this question because I'm trying to figure out whether my turbo is working properly. I'm under the impression that it only works intermittently.

Lately, the 300SD has been a real dog on hills. This evening as I was driving up a steep highway entrance ramp, I floored it and got this glorious roar and the car took off. I was like, "wow where'd that come from?" . I've had a few of those moments since I bought the car 5 months ago. My previous car was a 240D, so I really had no idea what a powerful diesel engine feels like. I've read posts where guys describe a whining sound from the turbo, but I'm getting more of a low roaring sound.

I've already done a search and will check for play in the spool, and check the over boost solenoid. I've already cleaned the banjo bolt, it looked pretty good. There was also mention of turbo ring seals failing and oil getting into the intake manifold. I noticed a lot of oil seems to be dripping from below the intake manifold. I recently changed the valve cover gasket, so I don't think that the oil is coming from the valve cover.

Will a properly working turbo improve my mileage? I'm currently averaging 22 MPG's city/hwy. thanks

your turbo should make a high pitched whistle. check out some video on you tube that should give you an idea. The best thing to do is to install a boost guage. How much smoke do you get at WOT?

your car should be loud enough on the highway, that you cannot hear the turbo.
when did you last change your fuel filters? lack of hilly acceleration is usually fuel filters.
you could also have a worn out alda (the part the hose from the banjo bolt goes to.)

Mine sounds like the angels are singing on down from high. That should be fixed this weekend when I replace the manifold joint.

I never hear my turbo.

Charlie

You mentioned cleaning the banjo-bolt on the rear of the intake manifold. Did you follow through and clean the rest of the boost line from there to the overboost switch, alda and injection pump? Also, have you ensured the over-boost switch is not leaking? From your description, I would suspect the latter.

Another area that I've found that really is sensitive is the fill level of the transmission. Even one pint low has a major effect on power.

Also, sealing around the top edge of the oil separator, inside the filter housing, will help to nearly eliminate the oil problem there. Ensure the o-rings are good on the separator drain as well.

I could hear the turbo in my 1979 W116 300SD, which had great pickup. It was a whistling noise. At freeway speeds the engine was totally silent and there was a faint whistle of the turbo.

My 1980 w116 300SD is slower and I never hear any turbo noise. When I'm accelerating the engine roars. When I am on the freeway there is a lot of engine noise; it sounds like a roaring or grumbling. It lacks the power my 1979 had.

I take it this is because the turbo is dead. I think that the turbo is supposed to quiet the engine noise and produces a whistling sound. I liked my 1979 300SD because at 75 MPH it sounded like a jet.

We have lift off!
 

I bypassed the over boost switch, which I think is the small cylinder on the driver's side of the firewall that accepts the clear line from the banjo bolt, and it felt like I put a new engine in that car! What's the correct name for that cylinder/valve? Can I clean it, or should I replace it?

The engine was much quieter on the highway and shifts were smoother. Does this mean that I should be getting better mileage now that my turbo is working? Liberating the turbo and installing Bilsteins on the same day, life is good.

Overboost solenoid. They are a dime a dozen at the junkyard on practically all benz models.

Thanks winmutt, can I go a few days without one? I'm a pretty conservative driver.

I've been running without one for almost 8 months.

I'll fix it eventually.:rolleyes:

Absolutely. It is a failsafe mechanism not an every day use one. Even without it and your wastegate hose off you wont kill the engine right away.

To bypass the over boost, shall I simply disconnect the hose from the banjo bolt and the hose to the alda, or connect the two?

The overboost switch mount on the manifold is where I install the boost gauge take-off.

It's more important to see the boost, than to have an ever present nanny device that will probably never trigger in lifetime of the vehicle.

I've never heard my turbo; but, I certainly feel the acceleration boost when it kicks in at 2k rpm.