TysonChicken

Over the past six months, I've replaced my secondary turbo four times. My primary turbo has been 100% fine.

I thought the first two failures were just bad luck. I really started digging for causes after the third failure, and found switched hoses between the charge relief valve and the y-pipe flap. I fixed this and installed a rebuild from Majestic Turbos (the others were Pettit rebuilds), but it quickly failed too.

The last three failures all happened the same way: right after installation --within a few miles of running 10 psi above ~4k rpm--, the secondary turbo failed (huge clouds of oil smoke out the tailpipe and oil dripping onto the ground). These happened during "careful" driving conditions. In all cases, the oil seal on the exhaust side of the secondary turbo failed.

I've pulled the engine compartment apart, testing all the actuators, solenoids, pressure tanks and vacuum lines. Everything's worked (according to the workshop manual). The turbo's oil lines are completely clear, and their drainage back into the engine is fine.

The only questionable thing that I found was a check valve (the one inline with the pressure tank). The valve worked one-way like it should, but seemed to be real restrictive. I got decent air flow through it with my air compressor (~10-15 psi), but there was no way for me to blow through it with just my lungs. Is this normal??

Help!!! I'm ready to drive my Rx7 off a cliff. Thank god there aren't any cliffs in NW Florida.

DaleClark

iTrader: (55)

First off, a buddy of mine and I went through around 5 turbos from Majestic Turbo in Tampa - EACH ONE blew oil. They just can't rebuild a damn turbo to save their life. Pettit might also be getting their cores from them.

I seriously doubt it's something with your control system. I think you're looking at an unfortunate string of bad luck.

Try BNR Supercars - I've had good luck with my turbo from those guys.

Dale

TysonChicken

Hey, Dale. Actually I went through Majestic Turbo of Waco, TX. They seemed to be a-okay, but who knows.

I would agree about just having bad luck with rebuilds, except that "turbo #3" was straight out of Cam's car. It had been rebuilt, then run in his car for 5k miles with no problems. But as soon as it was installed and run in mine, it spewed major oil.

My primary turbo was rebuilt by Pettit at the same time as "turbo #1," and it's been fine for 1.5 years...even though I've lost 4 secondaries.

What do you all think?

Tyson
Pensacola

DaleClark

iTrader: (55)

Hey Tyson! I just realized it's Tyson from autocross . I know, I haven't been out there in forever...

Anyhow, have you checked your PCV system? If you have a bad PCV valve or something else wrong with that system, you can pressurize the crankcase and blow oil smoke.

The only other thing I can think of is something way wrong with the turbo's oil return line - if it's stopped up or something, oil will back up in the turbo and blow out the exhaust side. The oil feed could be a culprit, but that typically takes longer to become a problem.

Try running the car with the oil fill cap off - that should prevent crankcase pressurization. Just try it to test - driving a lot with the oil cap off could lead to a messy engine bay .

There is also a possiblity that it's bad oil seals in the engine, but finding that out is tricky - the turbos make the troubleshooting tough.

Dale

Snook

iTrader: (12)

dcfc3s read a lil more carefully it's the turbos blowing oil

DaleClark

iTrader: (55)

An engine pumping oil can look like turbos that are blowing oil, as can crankcase pressurization.

Just because someone says something doesn't mean it's true. Trust me, I fix computers and networks for a living . I personally know Tyson, and I know he knows what he's talking about, and there's no good reason for 4 turbos in a row to blow oil - it's likely something else, not just the turbo.

Dale

Snook

iTrader: (12)

when I read it you made it sound like he was replacing turbos for nothing and it was something else blowing oil the entire time on all the sets but I see what you mean now. BTW not trying to make you look dumb but you contradicted yourself when you said it's most likely a string of bad luck with the turbos and then you said it's most likely something else not the turbo. I think it's something else and not the turbos but it scares me that something like that in the control system being faulty can make you go through turbos. I have also heard of people installing multiple sets of turbos from companies that just don't know how to rebuild them but pettit come on now there's no coincidence here.


that is really horrible. If I ever had a problem like that I would not be happy AT all and most likely bye bye 7.
My turbos were rebuilt by pettit in 1999 there's about 35K miles or more on them now and they are running great. I've run them between 7psi-12psi the last year in both sequential and non seq and had no problems at all. I just wish my wastegate was ported that would have made things much easier.

good luck hopefully some more experienced member than me can nail down the problem.

Drifter93

Majestic turbo in Waco is a good place to get turbo’s rebuilt but I have noticed that when it comes to rx7's the seals they use just cant stand up to the heat that are cars put out.

TysonChicken

Dale, I think you hit it on the head.

I was reading through Corky Bell's book, Maximum Boost, last night and he mentions "plugged crankcase breathers" as a potential cause for oil in the exhaust manifold (he's got a great trouble/cause table on page 180). Oil drains out of the turbos into the engine via gravity only, so high crankcase pressure can impede the oil flow. This can back the oil up into the turbo, and force it out the seals.

That got me thinking. I removed the PCV valve a long time ago. But about six months ago, I installed a homemade oil catch in the breather line (from the oil filler neck to the primary turbo intake).

I blew through the line last night, and realized that it had much more resistance than the stock setup (which would cause an increase in crankcase pressure). My guess is that the crankcase pressure isn't high enough to blow out all the turbo seals immediately, just the secondary's turbine seal. I think that the primary turbo is a bit more protected from this problem because its got an additional length of oil pipe to act as a reservoir.

So the next question is: does the secondary turbo need to be rebuilt? If my crankcase pressure problem is fixed, then will the turbo seals "reseat" automatically? The car was only driven for ~10 miles with "rebuild #4."

Thanks for the help!
-Tyson

DaleClark

iTrader: (55)

Hey Tyson -

The seal on the exhaust side of the turbo is almost identical to a piston ring in a piston engine - it's not like a rubber seal or something that can blow out. I would try re-examining your PCV system and see what you get. Most likely you haven't done any damage to the turbo - with oil backing up due to PCV problems, oil will flood the turbo's housing, back up, and leak around the exhaust seal. The seal on the exhaust side is to keep exhaust gasses out, not keep oil in. Though a real bad one will blow oil .

Anyhow, keep us posted - sounds like you're on the right track.

Dale

TysonChicken

Dale,

I just spoke to Majestic Turbo and they confirmed what you just said...no rebuild necessary. You're on top of things, man!

BTW, do you still have an old, useless 13B rotor sitting around? I asked you for one a long time ago, but haven't seen you in a while (and I lost your phone number)!

Thanks again to everybody for their input. My stress levels are back down to normal. I don't feel the need to drive my Rx7 off a cliff anymore.

DaleClark

iTrader: (55)

PM'd ya, Tyson.

Dale

turbojeff

iTrader: (30)

I used Majestic for a turbo rebuild on a TII once. It is still going strong to date.

Sounds like you guys have it figured out. Good luck to you.

cewrx7r1

iTrader: (2)

Have you checked the oil return pipe, maybe it is stopped up.

A few of us in Houston have been using Waco Majestic for years without any problems.