7.3 IDI definite exhaust leak

[The_Josh_Bear]

Yes, I know this is an old thread I'm curious to know if the OP fixed his problem, and how much it improved the boost?

A little background on mine: I put a used factory turbo setup on my 7.3 NA IDI (including a little Ultra Copper RTV on the slip joint). It made the stock 7 psi with the fuel turned up 2 flats, so I figured everything was working, although there was more than spec radial play in the well-worn turbo. I wanted to turn it up to 10-11 psi (no studs), but it would not go higher even with the wastegate forced closed... I can make plenty of black smoke if I floor it even with the turbo spooled, too.

Anyhow, several thousand miles later, even on a cold day it won't make more than 5 psi@2000-up (55 mph in 5th gear), and only about 2 psi at 1500.

I don't see soot under the turbo piping and no audible exhaust leak. Before I go to the PITA of removing the turbo (not to mention the expense of a good rebuild), could a small pre-turbo leak really cause this much of a difference? A 2" pipe has a lot more area compared to a gap with a .020" semicircle, which would be quite audible...

True... but wouldn't compressor wheel contact with the housing make really ugly noises (and very little boost)?

I'll definitely check - it was above spec but no contact when I installed it - but still don't know how critical a small exhaust leak might be vs. the effect of excessive radial play?

I got a turbo kit off ebay, all the parts were there but the turbo was clapped out. However, I didn't have a way to check the play by spec and had never had a turbo before, so I didn't have a good idea what I was looking for.

I installed it and ran it as the compressor wheel wasn't hitting the sides that I could tell.

Never got over 5psi. Eventually I pulled the intake and could see the wheel spinning, then with throttle it would spin while rotaing on an eccentric axis, so the shaft was actually traveling around in a tiny circle!

Because of all the oil in the intake, it would contact the sides of the housing and wore the compressor wheel down so it didn't touch the sides of the housing without a ton of pressure with my hand.

I said all that to say I've been there and an out-of-spec shaft is a real problem, leads to very low boost and as other have said will at some point send parts into your engine!

 

[DrCharles]

Thanks for the detailed case report... Once it warms up a little, I'll start pulling it off and ship it to Classic Diesel. Guess I should not depend on the screen to catch flying turbo bits

 

[IDIBRONCO]

No you shouldn't. Most of the pieces will probably be small enough that they'll pass right through that screen. At least at first.

 

[DrCharles]

Update: I bought one of those $200 Chinese turbo cartridges and could make the desired 10-11 psi with the wastegate disconnected. But it only lasted a year before the occasional unholy squawk (blades scraping on the housing) started. I thought for the price it was worth the experiment, but expected a bit more than 1 yr of occasional use...

So I finally pulled the trigger on a CDD turbo with upgraded wheel, and put it on today, with copper RTV at the slip joint.
Unfortunately there is now a massive leak at the slip joint and very little boost either. It looks like I didn't "clock" the exhaust housing exactly the same as before, and I think the Y isn't going far enough into the downpipe because there's a slight angle.
I'd love one of those Idioit up-pipes but don't have another $700 after buying a $900 turbo Time to start plumbing and hopefully sealing!