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Okay, I'm not exactly sure why I did this, but when I bought and installed SPG9's Stage 2 APC box, their balanced/ matched fuel injectors and Rising Rate Fuel Pressure Regulator (RRFPR), and the Advanced Ignition Diaphram (AID) device, I also ordered their replacement heavy-duty Bosch Turbo Bypass Valve (hooter) and a higher-pressure Wastegate Actuator. I did the hooter a couple of days ago, and the wastegate yesterday. I'm still tweaking the wastegate. I'll tell you about the hooter first.
If you read my Headlamp/ Hood removal post from the other day, you know that I took the hood off my Swedish Beastie for the first time last Thursday. It's definitely a job for TWO people, though I managed to get it off myself, tearing a plastic tee fitting on the windshield washer hose as I did it. The CORRECT method is: 1) take off the washer hose, then 2) remove two bolts and lift the hood off with TWO people! A friend of mine told me that he puts a blanket on the roof of his car and carefully rests the hood upside down up there out of the way. That might be a good option if you don't have a lot of room in your workshop or you're working outside, but be careful if it's windy! I've got plenty of room inside my garage, so I stood mine against the wall on a thick pillow with some towels draped over the top edges to keep it from scratching against the wall.
Anyway, if you're going to be working up there in the front of the engine behind the radiator, do yourself a huge favor and just take the hood off. I wish I'd known before how easy it was to take it off; there've been numerous previous occasions when it would have made my life a lot easier!
The hooter valve sticks out of the heavy plastic intake pipe which runs from the Air Mass Meter (AMM) to the intake side of the turbocharger. To get to it, I decided to remove the METAL pipe going FROM the turbo to the intercooler first. That was pretty easy -- just some hose clamps to loosen, and it came right off. It was pretty dirty on the outside so I set it aside on some rags so as not to mess up the Garage Mahal too much.
The intake pipe was a little more complicated. Hose clamps secure it to rubber boots at both the turbo and AMM ends. Additionally, a hose runs from the hooter itself to the throttle body. I loosened that clamp at the throttle body and pulled the rubber hose free. An air sensor line runs from the top of the pipe to the APC solenoid atop the radiator, and it pulls right off, too. A vacuum line goes to the hooter, and finally, some odd metal fitting plugs right into the side of the intake pipe. With some gentle coaxing and wiggling, I disconnected the whole thing and got it free of the engine. Not to belabor this too much, but it would have been about ten times harder to do this if I didn't have the hood off and had to reach in from the sides! What a pleasure it was working from in FRONT of my engine compartment for the first time!
When I disconnected the vacuum line to the hooter, the tip of the line broke off in my hand. It was old and brittle. It must get hot down there next to the air-cooled turbo... a silicon vacuum line set is in my future, I'm sure. For now I just took some new rubber tubing and replaced that vacuum line... I think I've replaced almost every vacuum line in the engine compartment at some point this summer. This particular vacuum line was between two and three feet long and ran from the hooter, around the thermostat housing, under the intake manifold, past the oil filter, ending at a tee fitting on the firewall end of the manifold. Routing it made me realize what a mass of snakes we've got in there!
So now I had the odd-looking intake pipe assembly in my hands... the pipe with the hooter and its rubber hose still attached. I took it aside to clean it off. Man, was it ever dirty. The hooter was held in with a simple clamp, which I removed. Then I took the pieces over to the trash can, and using paper towels, I wiped all the accumulated road grime off the outsides. It was a good thing I did, because I found that the plastic pipe had a split in it right where it connected to the rubber bellows at the AMM.
This pipe is on the suction side of the turbo, so it isn't subject to high pressures like the metal pipe on the outlet side is. Still, I didn't want air getting sucked in through the crack, bypassing my air filter and the AMM. I sealed the crack by squeezing the pipe together and winding duct tape around it. It looks a little funky, but it's functional -- I'll replace that pipe someday, but the repair will hold for now.
Putting in the new hooter was really a snap. After I cleaned the pipes and the rubber hose, I put the new one in and tightened the clamps. That was a mistake, and I ended up undoing the clamps again as I fit the part into the car. More on that later, but first:
While I had access to my AMM, I decided I'd clean it out with some electrical contact cleaner spray. I'd never done this, but people on the board have talked about it, so I figured, why not? I was really amazed at how fine the hot sensor wire is inside the AMM. Mine looked clean and shiny inside, but I liberally sprayed it with electrical contact cleaner anyway... the non-corrosive kind that doesn't leave any oily residues.
And as long as I was in a cleaning mood, I thought, heck, I might as well clean the Automatic Idle Controller (AIC) valve. An electrical plug on the top comes off with a squeeze and a pull, and the two hoses connecting it to either side of the throttle butterfly come off easily. Then I used a 10mm socket with an extension and ratchet to loosen the AIC clamp, and the AIC slid right out. I took it over to the deepsink and sprayed carb/throttle body cleaner into the valve on the bottom, reaching in with my fingertip to move the valve a little bit and ensure it was free. I probably shouldn't have done that, but it turned out okay, as you'll see.
Purely out of scientific curiousity, I got out my MityVac handpump tester to look at the two hooter valves. The one I was taking out was a Bosch replacement unit I'd had installed a couple of years ago -- it was practically new, and looked new once I wiped it off. Looking into the end of it, I could see the rubber diaphram that sealed the bypass hose. The new SPG9 unit had a brassy colored metal disk in there, a reinforcement to handle higher (18 - 20 psi) pressures. When I put the MityVac on the vacuum control line, both of the hooters opened at exactly the same level of vacuum. I didn't really expect to see a difference, but it was interesting testing them.
So, I put the AIC back on, put the AMM back in, and then took the intake pipe assembly with its new hooter installed and went to refit it into the car. This is where I ran into my first snag. I didn't have the hooter and its attached rubber hose properly aligned when I tighted the clamps, and now the thing didn't want to go back. After a few minutes of struggle, I removed it again, loosened the clamps so that the hooter could rotate in its mount, and then put the pipe back in. You have to spear it onto that metal fitting in the center while getting the ends into the rubber bellows at the AMM and turbo. I first tightened the end clamps going to the turbo bellows and the AMM bellows, then attached the hooter hose to the throttle body. At that point, with everything more or less where it was supposed to be, I had to reach in and tighten the clamps on the hooter. I then reattached the hooter's new vacuum line.
Next I reinstalled the metal pipe from the turbo to the intercooler. It had a little oily blow-by residue inside, so I cleaned it first by running a rag through it. It looked like new when I put it back. Once it was in place, I could reattach the APC line to the intake pipe. Done!
I triple-checked all my connections, hoses, and did my standard tool count, then crossed my fingers and started the car. The idle went to 1500 RPM, and I immediately knew why. My wife was standing by as I did this, and noticed the high idle immediately. (She also noticed the hood of the car was standing against the wall and was amazed by that! :D ) With the car running, I hopped out, took a screwdriver, and tapped the screwdriver handle against the AIC unit. The idle immediately returned to normal, the Beastie once again contentedly growling its usual note. My wife probably thought I was a genius, so I didn't tell her I'd probably caused the problem by poking my finger in the AIC valve and rotating it around too much when I cleaned it. Let her think I'm smart!
She helped me get the hood back on so I could take it for a test drive. I tied up the washer hose until I go out and buy a new plastic tee for it -- got to remember not to use the washer until I do!
Road test: Everything worked normally. The only subtle difference I could detect was that my idle seemed a little smoother; the up/down oscillation at around 800 RPM seemed just a little smaller in amplitude and shorter in frequency than it had been before. No doubt that had something to do with cleaning the AIC and/or the AMM, rather than replacing the hooter. A turbo boost run on the highway revealed nothing out of the ordinary -- still showing 4/5 redzone steady boost as before, with no ill effects when I let up on the throttle. Re-application of throttle (boost, let up, boost again) gave me nearly instantaneous boost, indicating the turbo wasn't spooling down and the new hooter was "doing its thing" properly.
Next step, the SPG9 wastegate controller. Unlike the hooter, it was no picnic. I'll post on that tomorrow. Oh, and Ron -- the stock hooter is in the mail to you.
- = M = -
'87 900T 159K
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