I have a 1992 940 turbo with about 160k miles on it. When I accelerate I hear a clattering noise, maybe a valve adjustment? Also when the engine is warm a knocking noise will appear. When accelerating the knocking noise increases in rate and by the time I'm in 2nd it's gone. This knocking noise can be loud or quite, it is pretty illusive also when I hear it popping it in neutral will make it go away. When acceleraeting my turbo gauge needle stays right in the middle. My turbo is leaking oil but not too badly (I think). Any help will be greatly appreciated

 

a crackling kind of clattery sound can be predetonation, aka knocking. use higher octane gas if you can, turbos need premium for best performance.

another common knocking sort of sound is 'piston slap'. the 'cure' involve a full engine rebuild or replacement, but they can have slap for 100K or more miles and still run OK.

your turbo boost gauge should be about 1/2 way on the left at idle or when decelerating with no gas, and when you lean on the go-fast, it should be about halfway to the right. if not, you got a problem with your turbo. or the boost gauge isn't connected (its a simple vacuum line connection).

 

I have soot that is covering the turbo and looks like one of the line is leaking oil. What would i need to rebuild the turbo? could i rebuild the turbo with novice mechanical skills? Also I was told that the knocking could be a lifter. I was thinking about going ahead and adjusting the valves soon anyway. does anyone know what the cost of a full engine rebuild would be? Thanks!!!

 

Clean it off with break parts cleaner (when cold) and watch as the black mess reappears. By soot do you mean oil grimy black stuff? I just think of soot as dry black powder. My car develops some too. Turbos do leak when they are wearing. Turbo rebuilding is not for the faint, but not very difficult. Over torquing the nut is probably the biggest faux pas. I like to mark the compressor wheel to the nut and to the shaft by a scratch mark. That way it should go back together close to the same way. Balance is very important to longevity, so I would not consider my rebuild to last as long as a professionally rebuilt and rebalanced turbo. I also had a turbo leak from the oil feed line. It got a hairline crack and was hard to pin down. When I did find it, replacing it was freakishly expensive, but I just got my former boss to hit it with a bit of silver solder and seal it back up.

 

any leaks in the oil lines just means you need to repair/replace those lines, not the turbo. if the turbo was failing, it would be gushing oil into the intake and exhaust, and making bad sounds. and little or no boost.

my 220k mile 740t has a perpetually oily intake path, it even dribbles a bit of blue smoke when its cold. once in awhile, it blows a blue cloud after I cold start it. even so, it only goes through a quart or two in 5000 miles of typical zooming around town. I'm a leadfoot. my boost gauge still pops right up to about 50-60% of the way from 0 to full scale, afaik thats about all the boost these have stock, and it pulls quite strongly in 2nd and 3rd gear even at low RPMs. my gas mileage sucks.

having a mechanic do a full rebuild on your engine? eek, don't even wanna think about that. many $1000's, far more than the car would be worth, unless you do it yourself and have a machine shop and you want a show car, new in every way. the bottom end of these engines lasts forever if they aren't run dry of oil. you should get well over 1/2 million miles on the main bearings and crank. even the top ends are quite durable, the valves last a lifetime if the engine isn't abused (for instance, driven with no coolant or oil).

if I had a B230F(T) engine fail like that, I do believe I'd be finding me a replacement used motor.

Treated with any sort of respect, these are incredibly durable and long lasting engines... my daughter's 240, was my wife's new car, it has about 400000 miles on it and its never even needed a head gasket (it has recently needed a camshaft seal, and some other minor seals and hoses). my 740T has blown its head gasket once (previous owner had the radiator fail and drove to the next exit), and after repair its still rock solid, although I suspect eventually I'll be buying a refurbished turbocharger.

 

Crazy to do a rebuild! The cost, and/or dubious quality of a rebuild, would be much more than what the car costs. Besides, there are plenty of good used motors on the market inside of cosmetically falling apart Volvos. On the West Coast a good used B230F or T can be had for $300 all day long...