My Exhaust leak

[Liquid Asset]

Ok, After taking all of my old exhaust blankets off yesterday I found what appears to be the leak. I am having trouble Identifying it. It appears that the exhaust leak is coming from the seal identified by the arrow on the right.

The part on the right that is not painted was covered by an exhaust blanket. It appears that the leak is coming from where the middle arrow is. But I can not imagine that there would be a leak there. Doesnt the large spacer keep the water in the exhaust manifold?

If yall could shed some insight onto this I woudl appreciate it.

 

[Genesis]

That is definitely a problem

 

[Liquid Asset]

By the way, does anyone have a breakdown of this? I can not find it in my Detroit manual. I do not want to dive into this without knowing what I am looking at. I need to get it fixed ASAP so I can start using the boat again.

By the way, Can a Turbo leak exhaust between the intake and Exit side?

 

[hattitude]

By the way, Can a Turbo leak exhaust between the intake and Exit side?

If I understood you correctly the answer is yes.

There are two "chambers" to a turbo, both with bladed wheels, connected by a common shaft. If there is soot between the two "chambers" and it is not there because it was directed there by the exhaust blankets from an outboard leak, then you have a leak in the inside exhaust housing. I had a similar leak and had my turbo rebuilt. The problem was solved.

Your exhaust joint is a design I am not familiar with, but I have had good luck sealing problem exhaust joints with Silkolene 762 hi-temp jointing compound.

Good luck,

Bernie

 

[Genesis]

The hotpipe comes off with just the bolts that are obvious. Between the hotpipe and the manifold (which is water cooled by the engine coolant) should be a metal gasket.

It appears you have two spacers between the manifold and hotpipe - that's a bit unusual but was likely done due to exhaust geometry issues and is of no consequence other than giving you more bolts to remove.

Get new gaskets, clean up the mating surfaces, and coat both sides of the new gasket LIGHTLY with Silkolene. Reassemble. Note that the Silkolene will smoke to beat the band on first use - this is NORMAL as its a heat-set compound.

That should fix it, providing the leak isin't in the pipe itself - it PROBABLY isn't.

Take your time getting the bolts out if they appear frozen. The hot pipe and manifold are both cast iron and if you break either, or break a bolt off in the manifold, you will be most unhappy. The latter (broken or damaged manifold) is EXTREMELY bad as replacements are absolutely stupid expensive.

BTW, expect that your inter (or after) coolers are nasty fouled - exhaust lekas usually do that.

 

[Liquid Asset]

I am going to pull the Intercoolers and clean them. I know they are probably really fouled. The turbos are fouled too, I know this because they air filters were black after bringing the boat home from Ft. Lauderdale. I ususally woudl not have run the boat knowing I had this leak, but It had to come home so I could do the work.

My turbos are filthy too. But I think I may have an exhaust leak on one or possibly two of them. What I didn't know is are there seals that could have not been replaced when they cleaned the turbos back when we purchased the boat, or could it appear to have an exhaust leak because of the exhaust leak I have on the up pipe?
What is the opionion of exhaust risers. I have been looking around and there are some people who offer riser coatings that are hard fiberglass with fire retardant resin. Is there an advantage to that over the soft blankes which are a pain in the butt. I need to have new blankets made, but since I have them off, I could remove the risers and send them to someone for a hard coating.

 

[Genesis]

I would not with the existing hotpipes.

They erode from the inside and if they're original they may have only half (or less!) of their wall thickness left. You will eventually have to replace them. BTW they ARE available and the last time I had to buy one (I managed to break a turbo stud on Gigabite by being hasty instead of patient when changing a turbo) they only cost $150 or so - they're not THAT bad.

I like the hardcoat on the exhaust from the turbo back, but not on the hotpipes. Part of the problem is that the flanges have to be covered, and you can't and still get bolts in them. You do NOT want those flanges sitting out there without insulation over them - the burn risk will be extreme. You're talking about 800F+ temperatures in there....

I'd just do the blankets myself....

BTW the turbos can leak from the exhaust housing half-seals. Fairly common, especially if the exhaust from the turbo back is not properly supported and is putting too much torque on the housing. If you've got carbon there its probably not from this leak - you likely have two leaks and need to address both.

 

[Liquid Asset]

Here is a picture of the turbo. The arrow points to the area where the soot is located. I dont know where it si coming from, but I am sure there is a leak somewhere.

 

[Genesis]

Oh, you have those infamous turbos with Monmon clamps.... those things are known to have leaking problems.

Its the turbo. It'll have to be taken apart (the exhaust side) and re-sealed. While you're at it check the supports for the piping from the turbo back to the exhaust, and if its inadequately supported, do something about that to prevent it from happening again.

 

[SKYCHENEY]

Are you sure that's an exhaust leak there and not an oil leak? If oil leaks there it vaporizes on the red hot turbo and really creates a mess. Was there oil on the blankets?

 

[Liquid Asset]

Karl,
can you explain how to disasemble? Is this something I need to employ my mechanic to do, or is this somehting I can handle? It looks simple enough, but I do not want to get in over my head. I read the Detroit manual breakout of the turbo and It dosn't look to be a difficutl thing as long as I dont try to disasemble the shaft parts.

Plus, is there an upgrade I can do to prevent this leak in the future? or is this something that will continue unless I change the tubos to a different style/model.

 

[Genesis]

The band clamps can be loosened and it will come apart.

The problem is that the seal surfaces may have been compromised (eroded) by the hot exhaut gases. If so there is no fix other than a reconditioned turbo, as you can't fix that "on site" and attempting to use a sealer such as Silkolene in that place is dangerous (it could ooze into the turbo and cause a failure - turbo failures can be spectacularly bad with pieces going where you don't want, including down the intake or coming through housings allowing exhaust gases out which then immediately start fires, and thus are to be avoided!)

If you remove the clamp it has to be replaced - you cannot re-use those successfully. Some folks have tried it only to have the clamp break on them while under power, which usually results in a grenaded turbo AND a fire.

The big deal on preventing a reoccurrance is to check (and if necessary improve) the bracing of the pipes behind the turbo. Most of the problems people have had with these turbo designs are not so much due to the turbo design as to the exhaust bracing BEHIND the turbo. The pipes back there are HEAVY and the turbo is simply unable to take that load - they have to be fully supported independant of the turbocharger and tied to the engine so that there is no force applied to the turbo housing when the boat moves in a sea.

These are 8V92s, yes (looks like it from what I can see.) If so this is a known weak area in the design with the exhaust not being sufficiently supported aft of the turbo - its not hard to fix, but its something you DEFINITELY want to take care of as if you don't it will keep happening.

 

[Liquid Asset]

There is a brace 6 inches behind the turbo on the riser. It is a steel pole connected back to the engine. It has a metal spring in it to dampen vibration, but is exactly the same on both engines. There is not a support problem as far as I can see anywhere.

I do not understand why we can not re use the clamps. They only appear to be a band clamp. I know that the intake side of my turbos were cleaned when we purchased the boat as part of the deal a year ago. They removed the intake side of the turbos and put them back on. The band clamps were not replaced. That was obvious. Is it only the exhaust side of the turbo you can not use the clamps over? I do not mind replacing them if necisary, I just want to make sure I know what I am getting. Are these a Detroit Part?

Also, How do you determine that the seals can not be replaced? am I looking for a smooth surface? If I remove the band clamp and the slide the cover off the turbo, is there a seal that I will see? that seal will be against what should be two smooth surfaces? Sorry for all the questions, but I am looking to be prepared.

If the surfaces are not smooth and I can not repair the turbos, what is your recomendation? Wold you have the turbos rebuilt by a turbo shop, or would you purchase reliabilt parts? Got any Idea what the cost of these things are?

 

[Boss Lady]

You really need to make sure that you eliminate the oil leaks near the turbo. They all eventually develop problems and the best course of action is preventative maintenance, if you have enough hours on them I would look at replacement, this should buy you some piece of mind. If one is causing problems the others are probably not far behind, like Karl said you do not want a catastrophic failure with a turbo, these things spin at 100,000 rpm. There are many things that wear out on one, the bearings, and the various oil seals and air/gas seals. I just repowered mine with 8v92TAs and now have stainless steel exhaust (much better). Regular steel eventually fails due to the steel breaking down from corrosion and carbon loss in the metal. If you can stomach the costs stainless is the way to go. I will check with a buddy of mine tomorrow about the replacement turbos, I have not heard good things about reliabilt turbos, there is supposed to be a shop in Florida that offers a superior replacement and then there is OEM. I am already looking for replacement parts for my engines and the boat is not back in the water yet. Part failures are not a matter of if, but more like when. I intend to accumilate spares for the 8v92 since Detriot is trying curtail support for these and push their DDC engine lines. The military has these engines in several vehicle programs and parts are available if you know where to look. Your dealer will be towing the party line.

 

[Genesis]

The turbos are not very expensive - $1k or so for a rebuilt one. Consider having YOURS rebuilt/reman'd by a good shop rather than buying a Reliabuilt. These are either Garretts or AirResearch's, and are common.

The band clamps are critical items - I would not re-use them. A failure WILL cause catastrophic grenade of the turbocharger due to metal to metal contact.

I'd look at that support - you want absolutely rigid so the piping is a unit with the engine. Anything else is going to lead to failures. My boat had TWO supports on the crossover pipe after the turbo - the second was added by myself when I replaced the exhaust, as I felt one was insufficient. Both were solid metal, no springs.

 

[MikeP]

That strut is interesting - obviously the spring is there as a damper to reduce the chance of cracking the assembly due to engine vibration. At the same time, it allows flex in the exh system with the possibility of causing exactly the type of sealing problem that is occuring here.

The 8v71TI (our 1980 model, at least) uses solid struts; I wonder if the springed version was unique to the 92 or did they go to it on all later engines? I guess if DD put them in there, they must have had a vibration-related failure possibility that it was put there to resolve.

I totally agree with Karl - use new clamps if you disassemble the turbo. The price is insignificant and since you have to remove them anyway, do the best job you can!

Always some interesting stuff...

 

[Liquid Asset]

My riser does have two of those support bars. I just dont have a picture with the second one shown. It is in the same position behind the other turbo. I went down a pulled the the riser support a little bit and that spring is pretty tough. I think it would take a lot more ammount of force than I can put on it to move the spring. Something tells me it is a vibration dampener and not a weak point.

I will go get new clamps. Also, can yall clairify what would be an Identifying point of the Turbo not being able to be resealed. These are AirResearch tubos. Karl, You mention that the mating surface may be deteriorated. If i remove the exhaust housing, should I be seeing a seal on the mating surfaces and will that be where the deterioration is?

Sorry for all the questions.

 

[Genesis]

Yep - the surface will be visibly eroded. If it is, you're hosed.

 

[Liquid Asset]

One more thing. Where is the best place to get the parts for the Turbos? Detroit, or is ther a source for Trubo parts? I will be looking for the band clamps and the seals for the mating surfaces.

 

[Liquid Asset]

Today I spoke with a few companies that do blankets and hard coating of the risers. Appearantly, there is a lot of different information out there and I am not sure what would be the best way to go.

While all of the companis were willing to hard coat my used risers, some said that they may not be woth it because it is hard to determine what their useable life would be left. While that makes sense, no one could tell me exactly what it would take to determine that. One company quoted me $3850 a side to make new risers with hard coating. That goodness I was siting down. THis company would also not repair my exhisting risers if there was a problem with them. For example if the showerhead needed replaced.

I spoke with somone else, who would hard coat them for $750 a side, plus 2 hours labor per riser to prep. They said they would repair them if there were any problems, but that somtimes the stainless gets brittle and if you weld to it, it will crack because of age/heat cycles.

Both companies would sell me blankets, but they have to be made because they are not a standard part. Not a big deal, but it takes just as long as adding the hard coating.

What are yalls opinions on this, but most importantly, what is your opinion on Riser life on a diesel engine. They are stainless and outward appearances are good. they are only discolored, but look great in my opinion based on teh fact that they have been coverd with the blankets which I am sure held in moisture.

I do not want to throw good money after bad if they actuall will need replaced, but I just dont see where anything but the showerhead where the saltwater enters can have problems.

I have a local welder who can build anything on earth, but I would have to get a showerhead for him to weld on if there was a problm. Is that an option. I am afraid of opening up a can of worms I do not want to deal with this year. I can understand if they are going bad and would be willing to replace them, but I would love to stretch them as long as safely possible.