I just got done rebuilding my motor and last week I started it up for the first time. I noticed that when the water temp hits about 75 degrees C I have exhaust leaking through my v band flange. I took it off and reconected the down pipe but I am still having this issue. I dont remember seeing this before, is this normal?

 

If the vbands aren't prefect, they'll leak.

Everyone will swear by them, but after building an exhaust with them - I would never use them again unless I need to on the turbo discharage. They ALL leak a little bit on my car except the one on the back of the turbo.

So yes, its kind of normal.

The most typical cause of them leaking is warpage after welding.

 

Some leak, some dont. My old one did, and here is a link to a gasket material that solved it: https://www.rx7club.com/single-turbo-rx-7s-23/v-band-flange-gasket-467421/

First just try loosening the bolts where the DP connects to the MP and then tighten the DP to the turbo before re-tightening the bolts b/w the DP and MP.

 

you need good flanges, good fitment, and good welds with good penetration

 

Im fairly certain the error is all me. Cause I dont think it ever did this before. I will just take my time and do it right.

 

Its all in the build, you have to be real careful when you set everything up before welding.

 

well everything was pre welded when I bough it. I have the T04Z kit from rx7store.

 

Yeah...

My aspec manifold was built to use a TialV44. The flange they welded to the mani leaks a bit And its got a funny step to it so it can't really be surfaced.

V-bands although easy to R&I are not the most ideal connections for exhaust (or really anything) given the sensitivity to leaking. I'll use them only where needed, from now on its slip fits for this fella

I seriously have no idea how people get aluminum v-bands to seal on intercooler piping unless they've got some type of o-ring or machined seat that I'm unaware of....

 

I can help,

I think what happened was that the V-band flange warped during welding...No one ever accounts for this but it happens quite often. All the kits that I fabricate through Esmeril Racing have stainless V bands at the turbo and middle of two piece down pipe. They almost always warp at least a bit when being welded, some you can see with your naked eye.

I have a solution for this. I take the part once the V band has been fully welded all around...and I place it so the V-band sits with its mating face on the flat of my my 6" belt sander with 80grit sandpaper belt and I run it and ensure that it is sitting flat. You will see that it only touches on two spots at first. I leave it on there until the two "sanding marks" meet. This works every time and I've had no customers complain about leaks in their system, we've probably sold 35 kits with no complaints.

Of course there is a catch. If your V-Band is way too warped then you would have to remove too much material and it could end up not tightening at all with the clamp...but if this were the case you wouldn't be complaining about a "leak" because it would sound almost like you didn't have an exhaust

Try this, it works every time, just be careful with your fingers.

Chris

 

fixed. I just didnt have it on right. when i assembled it I tightened the bolts to the mid pipe first then I attached the vband. so I just loosed the bolts on the mid pipe and re-adjusted teh vband and tightened everything back up. no leaks. thanks guys for all you help.

 

if all else fails just weld the downpipe to the turbo, no more leaks.
Glad you got it fixed though.

 

OK just some notes from the 100+ vbands Ive used sucessfully.

SS vbands need to have a step in them to center them against the next ring. otherwise getting them to align is a pita.

Al vbands most always have an o ring and should also have a step.

I always use vibrant performance vbands *i am no way affiliated with them other than a satisfied customer.

When you weld the vbands dont start at one spot and go all the way around. work your way around like your torquing wheels.

Also make sure that your ring is clamped down in the vband assembly with its mate, in other words its all assembled as a v band clamp when you weld it.

if this is not possible, try tossing the pieces in an oven for a while.

silicone copper gasket may be used if all else fails.