rustynogood

I bought a 91 300zxTT in charlotte this w/e. Car ran great! spooling to around 13 psi. About 100 miles into the trip home. The car blew the pass. side plastic header on the radiator. As soon as this happened, the car lost boost. I never ran it hot. Pulled in the next exit and replaced radiator. Runs and idles fine,but boost gauge goes to right before 0psi and stops. I can tell the turbos are not spooling. A major lose of power at the pedal also. No smoke at all. Turbos never made any noises. Is there anything ei: vaccuum line or electrical connection in this area that may been knocked off during the radiator busting? Any direction of diagnoses would be greatly appreciated. I feel its a leak in the vaccuum system on the wastegates. Not sure. I do know that it seems fishy that I lost boost the same time the radiator exploded. Has to be a connection here somehow. Can someone tell me where the vaccuum hoses coming from the wastegate lead to? Also, Can I manually control boost on a 300zx with a MBC? Thanks for any help you can offer. Thanks!!

Rustynogood

91zxtt

I agree with you that it's likely a boost leak. Too big of a coincidence. When you say the header, do you mean the plastic side of the radiator? If so, thne that's insane. There are a couple vacuum lines that connect to the black intercooler hard-pipes right near that location that are turbo feed lines; i.e. they're under boost and aren't under vacuum at idle. There is a vacuum diagram in the factory service manual. I'm not sure where in the FSM, but I found it once. Check out Rizz's link page. You can download the FSM from there. I recommend you become acquainted with it. I know I have.

rustynogood

I have d/l'ed the FSM. I will check for diagram tonight. I have seen two vaccuum hosed connected to the hardpipes. They are connected succurely. And yes. The plastic header on the pass. side of the radiator cracked and exploded water everywhere with great force to say the least. Any possibilty of a electrical short from such a blast of water?

Also while checking my fuse panel under the dash. With the key in the on position. I have no power running to or through the 7.5 amp fuse labeled EGR/Starter. But the car starts and runs. I even drove it to work today. Car runs smooth. just lacking boost.

I am from rotary land. I have a 88 turbo II w/ t3/t4 hybrid. On this car, I have a manual boost controller t'ed in between a vaccuum source and the wastegate. Is this passible with the z32? If so I can make the car boost by using this method and rerouting some vaccuum lines. But would this confuse my ECU and possibley run the car seriously rich or lean? Maybe even cause damange? Any ideas here??
Thanks
RUSTYNOGOOD

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91zxtt

With a MBC you need an accurate boost gauge (OEM is not) and an upgraded ECU. If you were running 13 psi then I assume you have an upgraded ecu. Do you know which brand (ASH/JWT/etc.)? The risk is usually running these things too lean. Any chip that's worth anything will handle 13 psi. Anyhting over 15 psi and you'll want to start to think about upgrading your injectors. Running to lean causes detonation; which of course can lead to a burned piston or pistons.

As far as a short goes, yes it is possible, but the only things in that immediate area besides the PTU (not likely - car wouldn't run worth a sh*t at idle or up top, if at all) are connections that run to the alternator harness. There's the Hicas assembly and the power steering reservoir.

I wonder if one of your intercooler pipes could've cracked or maybe one of the rubber intake pipes could've gotten ripped due to the force of the exploding radiator.


I'd have to check my fuse panel for that fuse, but I have to guess that mine is there. See what happens when you install a fuse.

rustynogood

There is a fuse in the slot. But no power on either side. I removed fuse and probed the connectors. No power on either side. This I do not understand.

As for the 13psi. the factory guage or my :guesstimation" may have been off. Could have been anywhere from 11-13Psi according to the factory guage. Ihave checked the top four intercooler hoses. No cracks there. I do not believe this car has a chip installed. This car is "bone stock".

Are the wastegates more visible from underneath? I am use to alot more room under the hood LOL. I have yet to see a wastegate nor the vaccuum hoses that lead from either side. Do I have to take the intakes off to view the turbos?

91zxtt

Welcome to the wonderful world of Z32TT mechanical repairs. Isn't it fun?!?

There no power switched or constant? Weird. I forgot to check my fuse box. Someone help out Rusty and take a look at their fuses.

The wastegate on the passenger side is pretty much hidden. If you know where it's supposed to be, then you can feel it from under the car. The driver's side wastegte is pretty much out in the open, or as out in the open as they can be in this engine compartment. If you remove the turbo outlet piping on each side, then you can see the driver's side wastegate and the boost solenoids. If you remove the intake piping, then you can see the intake side impeller of the turbo. In order to see the exhaust side of the turbo, then you need to remove the downpipes; which is done easily with the tranny out of the car. It's significantly more difficult with the tranny in the car.

If you're running 11psi on a stock chip, then that's probably fine. 13 is too much on a stock chip. Don't trust the factory gauge because it's not accurate. If I were you I would get rid of the MBC and install an electronic one.

Sorry, but I'm running out of ideas on the boost problem. Are you 100% sure this thing didn't over heat?

rustynogood

One more quick question. I am sure the Cats are stopped up on this car. I smell rotten eggs all the time while driving it. Could this cause the turbos not to boost? Thanks


RUSTYNOGOOD

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91zxtt

It could reduce the boost, but not as instantaneously as it did in this case. Car could be running rich also.