'94 turbo control vac lines Topic is solved

[BlackBart]

I've had a funny random stumble with my 850T on acceleration, like a cracked boost hose. Sunday I dove into finding a hose leak or intercooler hose problem.

Found one of the vac lines broken in half at the clip on the rear of the head, others seemed pretty dried out.

My question is about the routing and connection of those hoses.
Here's the diagram of those three hose connections...

vacuum-hose-diagram-850.jpg (104.59 KiB) Viewed 138 times

The lower hose (yellow this diagram) goes to the boost control body, the middle (blue here) goes to the intake hose close to the filter box, and the upper (green here) goes to the bottom of the turbo body. (hard to get to that one from under the car).

I checked mine before I took anything apart, and the upper and lower hoses were flipped from this diagram. The parts diagrams I have don't name body #16 where they all connect. Are there ports inside it that route the vacuum from one hose to another, depending on what the switch tells them? Is it just a hollow body and it doesn't matter where the hoses connect?

I've had this car a long time, and I'm sure the first owner never touched any of this at 60k miles, so I doubt it was changed.

So I hooked them up per the diagram. Only drove down to the gas station so far, but nothing funny in how it ran, and I had good acceleration. (Also tightened all boost hoses I could reach and checked for cracks)


Old & Busted

Other end broken off

They were all dry and just snapped off.

All new. My blue goes to the bottom of the turbo housing. My red goes to the inlet hose. My yellow goes to the boost control body.

[greg850r]

I just walked out and looked at 2 different of my 96 850 turbos and noted;
top line to pull off,
middle to air cleaner,
Bottom line to turbo body at the bottom.
That diagram does not match my cars. I think I remember there are 2 diagrams for 2 different year TCVs though and some cars are plumbed the other way. Perhaps the 94 was different and your diagram is correct for your year. Maybe they changed it for 95-96. Someone else here probably can confirm this.

Edit: While you are replacing the lines there is a 4th one coming from the middle of the turbo toward the motor (red one in your diagram) that goes around the driver's side of the head and connects at the intake for full time vacuum. It's probably as bad as the others.

[abscate]

You have found the other one of the 6 hose connection permutations that will work as planned.

The turbo control valve connects pressure from the turbo spool to either the waste gate (red) or dump (blue)

If the spool pressure (green) and waste gate lines are switched, the valve is connecting them exactly the same.

the other four combinations of hoses will not work correctly'

True mathematicians will cringe at my use of the words permutation and combination here, but thats why Nobel doesn't give out a prize in Math - the world hates you all, since you neither exist nor are you unique.

[BlackBart]

Where does that leave my son the fizziks major?

So my combination is ok, that's good. That diagram came from the 1994 files at Volvo parts webstore...
https://www.volvopartswebstore.com/show ... evel=24662

Greg - I saw that fourth hose back there. It was better than the others but I should probably change it too. I think I have enough of the blue left on the spool.

Thanks!

[BlackBart]

Wow what a blast! This thing is quick!

I forgot what a solid car this was and how fun to drive. So much lower than the XC.
My engine is relearning the correct A/F mixture without a vac leak - my range went from 30 miles (yike) to 40, 50, 70, 90, 105 while I ran errands and zipped out the freeway to the airport. Stood on the brakes a few times to clean off the rotors. One might be sticking a bit.

[erikv11]

Wandering off topic but: watch for rusting aftermarket caliper slide pins. Factory and 25 years old are not much of a worry, but if the calipers have ever been replaced then I'd pull them and grease them now.

[BlackBart]

OK, I'll look at that, thanks. It's been sitting for a while.