steve-z

Ok I originally did my DP install without using new gaskets and had an exhaust leak from the turbo manifold to downpipe connection, although the downpipe to main cat was fine. After searching a bit I went and got new gaskets and just finished with the re-install of the DP with new gaskets; however, I'm still getting the same exhaust leak.

When I first start up my car the smoke is visible for about the first 10 seconds or so until the car gets a little warmed up and I can see smoke seeping out of the connection.

One thing I noticed when I was putting it on for the second time was that the gasket doesn't line up correctly with the downpipe. Take a look at the pic below, on the top right part of this pic the inside gasket edge is actually overlapping the inside of the downpipe connection - on my precat this wasn't the case. Could this be the problem?

FYI it's a Pettit SS Downpipe.

Str8Down

I doubt that is you problem, that should be just fine. Did you reuse the studs or replace with bolts? Your DP may not have as thick of a flange as the Precat did, so the studs could be too long. Replace them with Allens if you haven't already.

steve-z

I replaced them with bolts, one allen for the hard to reach lower rear and then regular bolts for the other 3. I properly torqued them down with my torque wrench according to the shop manual specs (37-52 N-M if I remember).

Str8Down

And you are sure the bolts weren't too long? I would almost bet anything that the gasket is not the problem. Put something that you know is flat for sure on the flange, see if it is warped.

steve-z

Good call on checking if it's flat. The allen bolt came in the package from Pettit so I'm assuming it's not too long. I bought the other bolts to match the length of the allen bolt from Pettit (25mm in length I think).

steve-z

I squeezed under the car while it was running and leaking.. and I think I could see it all leaking from the forward bottom bolt on the downpipe.. like actually coming out from the bolt hole even though the bolt is there - I'm gonna try to get a new bolt or allen head for that location and see what happens.

SWAT81

iTrader: (14)

how about using some the liquid gasket? leave the new gasket then put some of the liquid gasket seal all around the edges.

1QWIK7

iTrader: (33)

well when installed mine, i waited til the car warmed up for about 10-15 min, went back under and re-tightened all the bolts and i was able to turn about 3/4-1 full turn on each bolt..

maybe you should try that..

steve-z

I've tried that to various degrees although I think I might let it warm up all the way, not sure if I've quite done that. I just replaced one of the bolts and could still smell the exhaust and feel the heat.. although couldn't see the smoke coming out on a cold start like I normally can (my car has visible exhaust for the first 10 or so seconds after a cold start).

I think I remember reading somewhere about adding some sort of fluid (brake fluid?) somewhere so that it would burn and you would be able to see exhaust pouring out where the leak is although I can't seem to find that information - is something like that possible or I am hallucinating? It would be helpful to be able to see the exhaust smoke so I can tell where it's leaking from exactly.

steve-z

Well I warmed the engine up to 180 and took another crack at the bolts.. none of them needed any further tightening.

steve-z

Ok after a couple days I'm back at this.

For about the first 15 seconds when I start my car up there is visible smoke out the catback (it's done this ever since I've had the car through 2 engines). I used to be able to see the smoke then pour out from around the turbo manifold -> downpipe connection although that seems to be gone. But now I'm paranoid that it is actually still leaking and I just don't know it.

The car sounds different when I drive but I think that may be the turbos spooling up? I've read that you hear those pretty good after putting in a downpipe, I've never been in other rx-7s so I can't tell if what I'm hearing is the turbos or an exhaust leak.

Is there anything I should be looking for that would let me know my exhaust leak is still around?

adam c

iTrader: (2)

Take your car to a muffler shop, and have them check it.

SlvrRexx

When i installed my turbo I had a similar problem.... It seemed like I could get the connection between the dp and the turbo manifold to be tight enough. what I eventually did was, i reused the old gasket as well as a new one.... this allowed me to get the connection as tight as i needed for no exhaust leak.

steve-z

Just drove it around for a bit and I think all I'm hearing is the turbos spooling up, but when I popped the hood afterwards it seemed a little hotter than normal and a hint of exhaust. I could see some visible smoke coming up from the turbo manifold/downpipe area although when I crawled under the car it appeared to be coming from below that connection, so I'm again not sure wtf is going on. Think I'm gonna take it into a muffler shop like adam c suggested and see what they think.

dgeesaman

iTrader: (7)

Normal smoking is caused by the downpipe and stuff burning off the pb blaster, oil residue, etc. It does sound different. ATF is what you can use to make smoke - disconnect the TB elbow, run at idle, and inject a few drops (don't let anything else get sucked in!!!). Supposedly it doesn't take much ATF. I also had some luck using smoke from one of those insect-repellent punks and watching the smoke run over the connection - the leak will disturb the rising stream of smoke.

Did all of the screws go in without a fuss? (I had a screw that was being a bugger, turned out the tap in the turbo manifold had metal shavings in the threads - chased it with an M10x1.5 tap and it went together nice and easy.) That tight bolt caused the tightening torque to be absorbed by friction, and the reduced clamping force caused a leak. (Torque was all friction - not much clamping force). You might want to put a narrow flat washer under the heads, and use a dremel to grind away the weld that's real close to the bolt hole.

25mm is the correct length. What kind of bolt is it? You should have a Class 10.9 or 12.9 - anything less may yield and leak under the spec torque. (I've got a boatload of real high strength bolts and studs in this size if you want to save the search).

Liquid gasket will not work - temps here exceed 1000F, so I'm told (dull red hot steel is 800F+, and many people report that happening).

Dave

steve-z

All the screws went in perfectly - I could spin them in by hand quite a few turns until they just needed to be torque'd down to specs.

I'm not exactly sure on the bolts, right now I'm using 1 stud, 1 allen head and two normal bolts. The stud and allen head came with the Pettit DP and the others I got at the hardware store - so they probably arn't the 10.9 or 12.9 (I think I remember seeing 8.8 stamped on them?).

As far as the ATF trick to get it smoking I tried that just now, took the throttle body off and injected a few drops of ATF.. didn't seem to do anything, then I tried quite a few drops of ATF seeing if I could get it as far in as I could but again couldn't get any smoke. I searched some and people seem to get A LOT of smoke if they do this right so I'm not quite sure what I'm doing wrong, doesn't seem like a hard thing to do. Anyone have any tips on getting the ATF in to where it'll smoke for me?

dgeesaman

iTrader: (7)

8.8 is one grade below 10.9 (12.9 is generally only available in socket head cap screw form). Just use a torque wrench and don't kill them. Tighten in a criss-cross pattern.

Dunno about the ATF trick - run a search and I'm sure something'll turn up.

Dave

Rated R1

The easiest way to run ATF is to run a hose to the nipple on the intake manifold from a quart of ATF. Have a buddy rev your car and let it suck in a LITTLE bit of ATF it should make the car smoke a lot. I used this technique to diagnose a blown exhaust manifold gasket.

I have a pettit DP as well. The allen head bolt was about 1/4" too long and I had to cut it down. I would double check that area why you are in there.

dgeesaman

iTrader: (7)

Wait, I just read this more closely. Hardware store grade bolts are generally 5.8, which is just too crappy for this job. Are the cheap bolts on the leaky side?

Anything over 28ft-lb will cause a Gr. 5.8 to stretch, and once they stretch re-tightening won't fix it. (8.8 handles 45ft-lb, 10.9 handles 64ft-lb). The elevated temperatures require extra margin. 8.8 is as low as I'd go. Offhand I don't recall the OEM torque spec.

I seriously recommend replacing all 4 with a better grade of bolt. I have a load of them in 10.9 that I can mail to you for very cheap. You might find 10.9s in Autozone. The Mazda ones are several dollars per piece (nut and stud).

Dave

steve-z

Torque spec is 27-38 ft-lb. I checked on the bolts and they say OF 8.8 on them.

After driving it around a bit today and getting some dry roads I'm pretty sure there's an exhaust leak. If I go WOT it sounds fairly loud from the engine bay on the right side (different from the sound of the turbos as they spool). I think I can also possibly hear it rattling around some, although I'm not sure on this, it sounds like something is loose when I got WOT.

I'm gonna try the ATF as per Rated R1's suggestion to see if I can actually confirm it's leaking then I'm gonna try to use both new and old gasket. If all fails I'm taking it in to the shop.

steve-z

Alright I did the ATF trick (a tube into the bottom from the UIM nipple worked perfect) and could see the exhaust leak so I was assured it was there. Upon further inspection it was coming from the bottom part of the flange (turbo manifold side).

Took the downpipe off and on the flange you could actually see where the exhaust gas was getting out because it discolored the flange on the bottom section:



I took anything straight and flat that I could find and put it up against the flange trying to see if it was warped but it appeared perfectly flat, no warping.

While handling the downpipe I realized that there was a section of it just below the turbo side that was warped or twisted. I could feel that the steel itself wasn't smooth and it had a 'wavy' feel to it. I tried to capture this in a couple pictures that I highlighted the wavy part:







It definately didn't used to be like this before I drove around on it for a day or so (about 50 miles total). And now this warping or wavy part of the downpipe has me worried that there's something wrong with it. Has anyone else ever seen something like this? With the exhaust leak and now this twisted section I'm wondering if I should just try a different downpipe. I'm going to call Pettit tomorrow about this twisted section and see what they say.

Rated R1

Are you sure the hex head bolt is not too long?

steve-z

The ones on the bottom are the same size as the ones on the top, and are the 25mm length. The bolts themselves are digging into the ceramic coat on the outside of the flange, I can spin them in by hand until they are just about tight then I torque them down to specs. So there are no indications that they are too long.

FYI: the first time I installed this that it leaked I actually was using the 1 allen head bolt that came with it along with the 3 shorter studs that came with it and it leaked then as well.

How could I tell if they were too long? It seems like I'd notice because it wouldn't tighten all the DP all the way down, although this has never seemed to be the case.

steve-z

Just an update here, in what appears to be a warping or twisting of the downpipe as shown in the pics above, I talked to Pettit about it and they agreed that there appears to be some sort of distortion after looking at the pics. The bad part is now I have to ship it to them for them to verify and figure out what they're going to do.

I guess the precat is going back on so that I can at least drive the 7

bee

That sucks, I bought one of those cheep downpipes off ebay, installed it with the stock studs, and it worked perfectly.