[Supras] How do I locate an exhaust leak?

Sun Apr 20 11:51:32 CDT 2008

Hi!
     I am really glad that you were able to locate the exhaust leak.

In my opinion, the first thing to try is simply to retorque the manifold, starting with the rear most nut.
Do this on a cold engine, and torque according to spec., i.e 29 ft-lb.
If you can't torque the nuts because the studs are spinning in the cylinder head, then you'll have to rethread and helicoil the cylinder head for the manifold studs.  I am not aware of any write ups on this procedure, but it's relatively easy, especially if you've drilled and tapped threads before.  Unfortunately, you have to remove the exhaust manifold in order to do this job.  So, here is the procedure that I have done on my car:

1- Remove the exhasut manifold.  I removed turbo charger first, though I think you can remove the manifold without removing the charger.  Of course, turbo charger coolant and oil lines have to be disconnected from the engine. 
2-  Remove the studs where the threads in the cylinder head have stripped.  They usually will just pull right off, but if you decide to do all the studs, as recommended by the majority of the group, you can remove the remaining studs as well.

3- Get a close quarter right angle drill.  I used this drill
http://shopping.yahoo.com/p:Milwaukee%200370-20%203%2F8%20in.%20Close%20Quarter%20Drill:2003368642

I do not recommed a right angle adapter as I have tried this option and it did not work well for me.  You really don't want to drill a larger diameter than what is needed for the helicoil!

4-  Get a thread repair Helicoil kit.  Here is the part number for the Emhart kit I used: 5543-10.  This is a complete thread repair kit, minus the drill bit, which is 13/32 inch drill bit.  But I guess if you pick up any other brand M10x1.25 thread repair kit will work.  Follow the instructions of the thread repair kit.

5- The first step will be to drill out the stripped threads.  Be careful here, don't drill too deep into the cylinder head, and since it's aluminum, you can easily do that.  Check the depth, mark the drill bet with the length of the threads of the studs, and you can also place tape on the mark to stop drilling when you reach the correct depth.  This is why I like the drill I mentioned earlier, it gives proper control needed for this job.

6-  Follow the insturction on the rethread kit to tap the threads for the helicoil.  I used a ratchet, especially for the tight spot near the firewall.

7- Now use the tool provided with the kit to thread on the helicoil.  Work carefully and slowly on this one.

9- Now you should be able to hand tighten the studs (use new one if the old ones look bad) on the cylinder head.  Some people use high temp loctite, I didn't and don't have recommendation against or for it.

10-  Install a new exhaust manifold gasket.  Note, it should only go on one way, there is a notch, which should be on top IIRC, but check the TSRM.

11- Torque down the exhaust manifold nuts (use new ones if the old ones look bad), working outside to inside bolts.  Set torque to 29 ft-lb.

10- Reinstall everthing else that was removed, with new gaskets.

      My experience has been that after, say 1000 miles, the nuts on rear most will start to loosen up again, but one retorque (on cold engine) should keep them tight for good.

Hope this helps, and again, use the TSRM for proper torque specs and procedures.

Regards,
/Khalid, 90T

----- Original Message ----
From: LN <studioartist at yahoo.com>
To: Khalid Almufti <kalmufti at yahoo.com>
Sent: Saturday, April 19, 2008 5:45:41 PM
Subject: RE:How do I locate an exhaust leak?

Hi Khalid,

Thank you so much you are so right!!!!!!!!! I have
been having this problem for 5 years after the rebuild
and with your advice you were dead on it's the last
bolt near the end of the head which was shooting air
backward toward the firewall. I can't see the cause
but the bolt are whitened from heat.  How do I fix
this with helicoil?  Is there a write up you can
direct me to?  Can I do it with the manifold intact???

THANKS YOU SO MUCH.. I HOPE THIS GET TO THE LIST.  I
find this list hard to use.

--- Khalid Almufti <kalmufti at yahoo.com> wrote:

> Hi!
>    When I ran into this problem it turned out to be
> a leak around the exhaust manifold gasket, which was
> actually due to the exhaust studs threads stripping
> in the cylinder head (you should have all of them
> heliCoiled).  Even if an exhaust stud is heliCoiled
> into the head, the nuts need to be retorqued
> occasionally, but do so on a cold engine (trust me
> on this one).  So my advise is to check the nuts on
> the exhaust manifold (90% it's the one on the rear
> most location that will be loose, start there).
>  
> Good luck,
> Khalid, 90T
>  
>  
>  
> At 09:12 AM 4/16/2008, you wrote:
> >Message: 9
> >Date: Wed, 16 Apr 2008 03:06:26 -0700 (PDT)
> >From: LN <studioartist at yahoo.com>
> >Subject: [Supras] How do I locate an exhaust leak?
> >To: supras at supras.com
> >Message-ID:
> <58623.3731.qm at web30405.mail.mud.yahoo.com>
> >Content-Type: text/plain; charset=iso-8859-1
> >
> >I have an exhaust leaking sound in the engine
> >compartment area but can't tell where it is
> >originating from exactly.  I took it to the local
> >Midas shop and they say it's the exhaust manifold
> >which cracked.  Afterward back at home I took the 2
> >heat shields off the exhaust  manifold but could
> not
> >see any cracks ( at least visible to the naked eye)
> >usingboth a flashlight and mirror to see the back
> >side.  Can someone suggest a way to locate the
> exact
> >position for a leak??  Maybe it's in the down pipe?
> >How about using soap solution or will that won't
> work
> >due to the high heat ?
> 
> 
>      
>
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know-it-all with Yahoo! Mobile.  Try it now.  http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ