broken vacuum lines to bypass valve and turbo

[wilson850r]

Just a quick question. I know the vacuum hose for bypass valve is not connected but I also believe the hose from the TCV to turbo is not attached. 1996 850R and seems to run fine with no CEL. What effect is this having on the engine? I am not sure I want to tackle this one as it looks like both of these are no place for big hands and I don't have that tool for the clamps.

[mercuric]

The hose from the manifold to the compressor bypass valve on the turbocharger is quite important. Without proper operation of the compressor bypass valve, excess stress is put on the turbo's compressor. The bypass valve works to relieve backpressure from the turbocharger compressor wheel when it's spinning fast and you let off the throttle quickly. In this condition, the boost pressure "backs up" between the throttle plate and the compressor wheel. The bypass valve channels this pressure around the compressor, so the pressure doesn't push back on the fast-spinning compressor wheel. It creates a shock-like effect on the compressor. It also causes the compressor wheel to quickly spin down due to the backpressure, greatly increasing turbo lag when you get back on the gas. This line is very easy to replace and can be done in a few minutes -- just run it along the hooks on the side of the motor to the front; there is a nipple on the front of the manifold for it.

There are three hoses attached to the TCV. One goes to the intake tube just ahead of the MAF, the other to the compressor housing which supplies boost pressure to the valve, and the other to the turbocharger's wastegate actuator. It is also very important these three hoses are in good condition and securely attached, otherwise boost control will not work as intended.

I'm not sure what kind of clamps you have on there, but the factory clamps (should be like http://assets0.fcpstores.com/public/ass ... 1298036542) can be removed very easily with a pair of needle-nose plyers - they're basically spring-loaded, you just use the needle-noses to pull the three clips together to form a straight line, which releases the springy-pressure and wiggle it back an inch (thus not applying pressure on the nipple anymore), remove hose, remove clip. Personally I'm not a fan of these and replaced all mine with worm-drive clamps and very thick silicone hose. If you do this, don't over-tighten them or you'll break the plastic nipples.

The hose from the turbo compressor housing to the TCV is the most difficult, it is indeed pretty much impossible to get my fat hands down there. It is possible to access it from beneath, but without a fancy lift I generally prefer to work from above unless I'm already jacking the car up for something more intensive. I just did this a few weeks ago, took about 90 minutes working slowly and inspecting/cleaning everything in the region since I hadn't been down there on this car before. It went a little something like this....

To start, remove the PCV hoses from the intake tube near the turbocharger inlet, and disconnect the electrical connector. There's some annoying clamps on those PCV lines, more on that in the next paragraph. Loosen the worm-drive clamp attaching the intake tube to the turbocharger just enough to wiggle it off easily, but not so much the clamp falls off the end. A long flat-blade screwdriver or 7mm socket + extension work here. It will stay if you don't loosen it all the way. Leave the intake tube dangling at the turbo. Now remove the hose from the intake tube to the TCV near the MAF, and disconnect the electrical connector from the MAF. Undo the clips to the top of the air cleaner assembly, and remove the entire top half of the box complete with the MAF and intake tube still attached. The intake tube will be tightly attached to the MAF and can split if you try to force it off if it's hardened like mine was, hence why I recommend removing the whole thing as an assembly. The intake tube is dealer-only item, thus relatively pricey, and it's integrity is a must for proper operation. You should be able to do this without removing the lower half of the airbox, but I did so to free up more space and inspect everything underneath. Push the lower half of the air cleaner box towards the engine to unseat the peg on the firewall side, and lift up and out the entire lower half of the air cleaner box, detaching the fresh air hose towards the grille as you work it up. Now you've got a giant open space where you had no access before. You can now get your big fat hands (like mine!) down to replace the compressor housing to TCV hose, as well as all the stuff obscured by the air box. The TCV-intake hose and TCV-wastegate actuator hose are trivially easy. While you have this stuff out, it's a good time to replace every other vacuum hose in that area that looks aged. It's also a good time to replace the air filter if it's dirty, and access to the cap and rotor is really easy at this point if you haven't done those in 60k+, that's a quick job very much worth doing now. There's also several important electrical sensors (crank/cam position) in that area, and it's not a bad idea to undo the connectors and check for signs of deposits/corrosion/debris and clean up with electrical contact cleaner if warranted. While you're at it, clean up the air intake tube, including both nipple attachments for the PCV system. If you do clean the PCV nipples, make sure to get everything out and blow it out with dust-off or compressed air, so your turbo doesn't inhale whats left.

The only complication here is the special Oetiker clamps on the PCV hoses near the turbo inlet. These POS's: http://assets3.fcpstores.com/public/ass ... 1298036099 -- Those locking clamps, while some love them, are one time use and basically have to be cut or pryed off. I personally hate them, and have replaced all of them with standard worm-drive clamps. I inserted a knife blade into the joining sections and pried them open -- Sure F'ed up the knife though, but it won't be missed. You can also use a small metal cutting tool to simply cut them off, just don't mess up the plastic nipples either way. Once you replace these with standard worm-drive clamps you'll never have to futz with them again. Some may scold me for doing this, and it does take away from the "perfect OEM" nature of the car, but I honestly dislike them.

This is easy work, just go slow, take pictures if you have any doubts about reassembly, and don't get frustrated or do it when you're in a hurry. Perfect basic job to build your confidence level, if you ask me

[wilson850r]

I am kicking myself because I just spent last weekend replacing my ABS module that someone before me had tried to replace and stripped out two of the bolts. I replaced the intake tube with my Snabb one from the wrecked wagon and replaced a couple of lines but of course missed the turbo one or I broke off putting the down tube back in. I was just not looking forward to taking everything off AGAIN I just put on. I just did not want to drive the car if anything bad would happen till this weekend. I don't drive the car hard and can't believe it still runs as well as it does. Thanks for the info.