Is exhaust leakage normal????

[dustmote]

Hello all!

I have a 1997 GMC Savana 3500 RV with about half a million miles on it, and although it runs just like new as far as I can tell, I have a question....

With the "doghouse" engine cover removed in the cab, so that I can access the rear of the engine, when the engine is running, I can feel and smell exhaust blowing out from around the crossover to pipe seal connection. You cannot smell exhaust in the cab while the cover is in place, and I only noticed the issue when I by chance had the engine cover removed during another operation. When I hold my hand about 2" away from this seal, I can feel hot exhaust blowing out about as hard as if you hold your hand about two feet in front of your face and blow out medium-hard.

I asked a friend who is a retired heavy duty diesel mechanic of his opinion, as I believed that changing the seal was in order, and he told me not to bother with changing the seal because this amount of leakage is normal, and that these kind of seals are never a gastight connection.

I have a carbon monoxide meter installed in the cab [although in these days of cheap chinese made devices, I don't trust it with my life] but I'm about to take my family on a 3000 mile roadtrip and in the process of taking care of all the usual preventative maintenance stuff, I figured I should ask the experts on here what their perspective was???

This forum has been an invaluable resource that has helped keep Ol' Boxy moving down the road for quite some time now, so I also wanted to extend my gratitude for all the help.

Sincerely, Many thanks on behalf of my family,
--DustMote

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1997 GMC Savana 3500 RV with 6.5L Turbo Diesel HO

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I have the full factory service manuals for the 1997 GMC G-Van / Chevy Express Van which covers the 6.5L Turbo Diesel and I also have the Tranmission and Electrical Manuals from the factory as well....
If anyone needs any info, I'm happy to scan and upload whatever sections and diagrams yo need!!! Just send me a PM and/or an email to my email address in my profile!

 

[3500GMC]

I'm not too familiar with the van engines but I think they have a center mounted turbo and the turbo hot side is fed by two ribbed looking flex pipes. Sometimes these break.. Look for black soot too, as this is a sure way to find a leak.

 

[trouttrooper]

any exhaust leak right off an engine is NOT normal.

 

[dustmote]

Yes, it's the center mount turbo with the ribbed flexy pipes. They are NOT broken [at least visibly] and the exhaust is definitely coming out through the mating flange between the crossover and exhaust pipe. I'll get a picture tomorrow.

I guess my question is more so: are these "donut" seals supposed to have some leakage normally? If not, then obviously replacing the defective seal should fix the problem correct?

Many thanks!!!

 

[3500GMC]

No leaks of any kind is 'ok' with an exhaust system. That is my opinion of course.

There on the hot side you're leaving some performance on the table by letting some gasses/heat out that would otherwise be spinning that turbo.

 

[dustmote]

As much as this thing jumps when you hit the pedal, I can't wait to see how it goes with proper turbo operation! I'm not driving it another mile until I replace that donut.... My question was less whether it's OK to have an exhaust leak as I am aware of the hazards of carbon monoxide, but more so whether these donut seals were supposed to leak under ideal conditions....

Thanks again!!!

 

[NVW]

I had one go out on a K truck and lost 1/2 of my boost, they shouldn't leak.

 

[Turbine Doc]

No leaks allowed especially in a turboed engine where you need all available exhaust to spool the turbo properly

 

[littleboy]

On the vans with the center mount turbo the flex piece on the up pipes break and leak ....

 

[dustmote]

Turns out on a close inspection that it IS in fact the ribbed flexy pipe which goes from the passenger side exhaust to the turbo which is cracked and leaking.... The donut seals seem to be fine.

New problem: Does anyone know where I can get a hold of one of those little flex pipes? I haven't been able to find a junkyard which seems to have a 6.5l with a center mount turbo, and none of the autoparts stores seem to have a clue either. Am I going to be forced to go to the stealership for this one???

Anybody have some spare parts that they want to sell?? :-D

 

[jhornsby3]

I have found it at Orillie's Pep Boys and the local exhaust shop. NAPA and Carquest also should have it or can get it.

John

 

[dustmote]

You found the ribbed pipe such as shown in this image which connects the exhaust manifold to the turbo exhaust inlet??? I need the one for the passenger side, but when I contacted Pep Boys, the local NAPA, and OReilly's, and wasn't able to find anything.

I'm not looking for generic "flexy" exhaust pipe sections.... I need the part which can fit.
I guess I should have started out with pictures to try to make things more clear.

 

[jhornsby3]

So if you are wanting the exact parts used by the factory, you might be stuck with the stealer if they have or can get it. Looking at that I would cut the flex off of the ends and replace with easily obtained parts. But then I have the problem of needing parts when in areas of haveing long walks and the use of ones thumb. Yes i keep my robe and always have my bath towel and guide when I leave the driveway.

 

[dustmote]

Wait, you're saying that it is functional to just get "flexy pipe" for ordinary exhaust repair and cut out the bad section of the stock part, then weld the flex pipe into place?

Or can it be clamped?? I'm sorry, I've never had any experience with repairing exhausts like this.....

I'm not at all stuck on the idea of OEM parts, but if there is a drop in replacement that would be ideal, although if clamping one in can work.....

This pipe is under a bit more pressure than usual exhaust pipe I think due to it's position upstream of the turbocharger.

 

[jhornsby3]

I'd be for cutting out the old section and clamping in the off the shelf. And if it needs a foot of flexie then I'd get two feet and have spare to throw in the parts bin in the under side just in case when out and away from home.

When I replaced my exhaust donuts they did leak a tiny bit but quickly sealed with soot when I checked them about 200 miles later. That flexie will seal the same way if clamped tight.

But that is just me.

John

 

[Turbine Doc]

Instead of a corrugated ridgid flex, look at the flexes that have braided outer jacket maybe something along the idea of attached picture



cut out the leaking part and weld in the flex, I found it on ebay for $26 listing 170924573598 it was a 3.5 x 12" & probably way too big to fit under a "dog house" but it is possible they can be found in smaller ID

 

[Turbine Doc]

I just now typed in exhaust flex joint on ebay and came up with multiple options (200 listings) to view some even down to 1.75" so if you don't see it a vendor listing there might be able to get it for you.

 

[jhornsby3]

There you go. TD didn't just get you the part but the one that would look the coolest. LOL Good luck with your project.

John

 

[dustmote]

OK, well after ridiculously extensive googlin' ...... I've found sources for these parts as well as the manufacturer's names and numbers.

These little ribbed bellows type pipes which connect between the cylinder head's exhaust header / manifold to the turbocharger's exhaust inlet are called
"Pipe, Exhaust LH" and "Pipe, Exhaust RH" with General Motors part numbers 10239026 for the left, and 10239025 for the right.

They are available from several sources online who all trace back to Kascar.

65diesel.com has these and a LOT of other hard to find parts.

Right now the right side one is going for about 87$ plus shipping.

Kinda painful to me, but it might have to do. I'm going to call the stealership in the morning and see what their price is on it now that I know the part number.

The problem with welding a transplant in is that it doesn't seem possible to weld in a section of flex pipe from the exhaust shop because there isn't enough length of pipe to do the transplant without having to weld in a giant loop around to make room for the sizeable flexy pipe sections..... Although if you could find a section of flex pipe which was less than 4 inches nominally, you MIGHT be able to do it.

And given that any leak in this section of the exhaust system will rob the turbo of power and thus have a LARGE effect on the engine's total power output, I really don't think that using a clamp on patch piece is well advised.

My saving grace was that this part seems to be used on a lot of the Hummers and the HMMWVWTFs that use the 6.5L. So there are a lot of suppliers which typically cater to the military and government which stock these parts.

Anyways, thanks for the help guys.... Hopefully next time someone needs these things, they'll find this post and be able to figure it out easier than I did.

 

[dustmote]

Here's a picture I found from the factory parts manual that shows the exploded parts with my particular item of interest circled in red.