Turbo to exhaust elbow........any trick to acheiving a good reseal?

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dpb

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I swopped the exhaust elbows between engines yesterday (to test if one of them is responsible for one engine running hotter than the other). Straight forward enough job, but now both turbo to elbow connections leak exhaust, not much, so I can still do my test run, but can't leave it like that. There is no gasket on these and the mateing surfaces just but together under the clamp. Is it just a case of making a better job of cleaning the surfaces before assembly, or is there a sealant I can use?
 
may be off the mark,

not sure how this is achieved on outdrives (I suppose), but on mine there are 4 M8 bolts with nuts to hold them together and with a plain clean of the surfaces they mate nicely together and don't leak any gases.
Does yours have through bolts on the flange?

V.
 
dpb said:
No, its like a v shaped jubilee clip that fits over the flanges to pull them together.
Click to expand...

oh, pass, no idea. Doubt copper grease or some sort of paste would withstand the heat of the exhaust gases.
I guess you've cleaned the flanges carefully with emery cloth to get them nice and smooth, right?

V.
 
Lightly dress both faces with a file to make sure there are no high spots, then a light smear of fire gum might work, but be aware this stuff sets like rock, so use a minimal quantity.

Were the injection channels clear on both elbows ? A good soak in a strong solution of caustic soda will dissolve any carbon.
 
The attaching surfaces need to be clean and smooth so you need to put some effort getting them there. I don't think it gets superhot as cooling water is passing so this type of product will work; http://www.henkelna.com/product-search-1554.htm?nodeid=8797922918401
I used it myself and did not get any leak, now 3yrs after replacing one of my exhaust elbows.

I don't think the elbows last much more than 10 yrs on a outdrive boat so if yours are there about you may want to consider getting new ones while you are at it.
 
A_8 said:
The attaching surfaces need to be clean and smooth so you need to put some effort getting them there. I don't think it gets superhot as cooling water is passing
Click to expand...

agree on the clean and smooth
however, OP says turbo to elbow joint. I'd have thought it gets hot enough as the water jacket must be on the elbow not the turbo???

V.
 
Both the turbo and elbow are water cooled so not too hot, is it Mercruiser or Volvo? As others say get the mating faces smooth and flat, I use a fine flat file, if they are old and corroded the problem is cleaning them then reduces the amount of metal that the V calmp can bite on, I just did one for a mate and used the flat copper sealing ring from a Yanmar exhaust bend to give me a bit more thickness on the joint and the copper readily deforms to fill any irregularities. tighten it partially and then wiggle the bend back and forth a bit to get it centralised before final tightening, if it still leaks fill the groove in the V clamp with exhaust paste.
 
Yes, the elbow is cooled by seawater. The exhaust side of the turbo is however also cooled but through freshwater/coolant so I would say it probably don't get much more than 100 degrees Celsius, maybe a bit warmer close to the exhaust piping but still cool enough.
I've used a silicon product as above (up to 300C) and no problems whatsoever.
 
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dpb said:
I swopped the exhaust elbows between engines yesterday (to test if one of them is responsible for one engine running hotter than the other). Straight forward enough job, but now both turbo to elbow connections leak exhaust, not much, so I can still do my test run, but can't leave it like that. There is no gasket on these and the mateing surfaces just but together under the clamp. Is it just a case of making a better job of cleaning the surfaces before assembly, or is there a sealant I can use?
Click to expand...

No clue from information given as to engine, turbo manufacturer or for that matter what 'mateing' is.......

Pretty much two types of turbocharger/riser connection in regular use, either Garrett pattern four bolt flange or half Marmon flange. Garrett four bolt flange requires thin embossed stainless steel gasket.

Half Marmon flange requires no gasket.

However in practical use the Garrett style will work perfectly well with with a bead of high temperature silicone instead of embossed steel gasket. which can only be used once.

As usual attachments get doubled up!
 
Thanks for all the answers.
The engines are Volvo Penta AD41a diesels.
The turbo and the elbows are both water cooled, turbo by engines closed cooling system, elbow by raw water.
I definately could have spent more time on cleaning the faces (I just went over them with sand paper) so will have another go and will also use one of the suggested sealants.
 
This was a problem on the smaller cummins engined daf trucks with the exact same type of clamp set up, cure was to clean them up with a wire brush until they were smooth and then seal using silicone sealant, never had one come back ever.
 
If it's like mine, the elbow exhausts to a rubber bellow and then on to the exhaust riser. The issue can be that the engine and exhaust riser are a little misaligned. If that's the set up you have, make sure the clamps for the bellows are left loose until the clamp is tightened around the turbo to elbow interface; otherwise, you can end up with a gap which I think is what you are experiencing.
 
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