Jump to content
HybridZ
Mobious5

Broken Exhaust stud!!

Recommended Posts

I kept wondering why i had to keep replacing the intake/exhaust manifold gasket, why it kept blowing, and why i kept smelling exhaust in front of the car. Until i actually looked for the cause.

 

Turns out the #1 (front of car) exhaust manifold stud broke off in the head.

 

Most people would was take the head off and take it to a shop and have them remove the bolt. Or take a tap to it and drill it out yourself. Neither of witch i want to risk doing on the head.

 

So without removing the head. I would like to know are their any alternative routes i can take. Like a really good sealant or some type of special glue or spacer...?

 

thanks

Share this post


Link to post
Share on other sites

Short of a new magic trick, there us no whey to cure your broken exhaust stud problem except to remove it and then replace it. It can be done with the head in place but you will need to know what you are doing.

Share this post


Link to post
Share on other sites

If you are going to get it out yourself the first thing you need to do is soak the thread over night in PB Blaster (not WD40 or anything else).

 

If you have a welder, try tacking bolt head and shank on to the end of the stud then backing it out with a wrench. Otherwise, try getting it out with a bolt extractor (A.K.A. Easyout). Drill the biggest hole in the stud that you can while still leaving enough wall for the extractor to grab onto. Also drill it deep enough so that the extractor doesn't bottom out. I always tap the easyout into the hole so that it cuts its own teeth and grabs well initially.

 

Good luck!

Share this post


Link to post
Share on other sites

easiest thing i found to do was DONT mess with the easy out because you may make the situation worse than before (cause you cant drill out an easy out, just push it further back into the head)

 

MY suggestion is to upgrade the two outside bolts to 10mmx1.25 studs (because replacing the 8mm with another isnt really fixing the problem is it :)

 

drill out the existing bolt thats still in there (making sure you go through the center, use a punch if you have to) then drill the hole out to the right size for the 10mm, rethread the hole with a 10mmx1.25 tap, clean it out, your done

 

thing is find a good 10mmx1.25 bolt/stud or none of that matters, now you just have a big hole with nothing to put in it

 

and make sure the 10mm bolt fits in the hole of the exhaust mannifold or header your putting on

 

 

putting sealant might last you 4-5 days before it gets pushed/burned out, plus you wont feel good about that kind of repair

 

im 17 (with no patience) did this by myself, i dont have much automotive knowledge or even a 1 car garage

 

cool thing was i did buy a lot of new tools, new header, and came out better $ wise than if i had went to a nissan dealership (or even the local scetchy garage) to get them to fix it

Share this post


Link to post
Share on other sites

my wifes 280zx, is at the shop for the same reson right now.

 

they said that my engine mount was broke so that's why my head studes broke in the first place. so make sure if yours i broken to replace it.

 

so it took about 3 days of spraying it with penitrent an playing with the bolts to get the 1st one out {all others came out no problem helps that we dont drive our 280's in the rain}. but if all falls just get the head takin off an do a valve job. but make sure that u arnt getting riped of on labor charges.......500.00 in labor JUST to get the old exhast mainfold off....an other 150.00 to put the new one on.....:lol:

 

 

chris M.

1981 280zx {gt35r turbo build underway}

1983 280zx {wifes}

Share this post


Link to post
Share on other sites

 

MY suggestion is to upgrade the two outside bolts to 10mmx1.25 studs (because replacing the 8mm with another isnt really fixing the problem is it :)

 

 

Neither "solution" addresses the real problem. An 8mm stud should be plenty strong to hold the manifold in place assuming there are no other underlying problems. The real problem is probably that the bolt is corroded due to water intrusion from a current or previously leaky thermostat housing and/or the manifold is warped...which was probably also caused or made worse by the leaky housing. I think people don't notice leaks there because it runs on the hot manifold and evaporates up quickly.

 

Mobious5 - After you remove the manifold, check or have it checked to see if it is true. Install a Helicoil insert instead of just threading the aluminum. Apply anti-seize to the treads of both the insert and the stud. If you use a larger stud make sure you open up the hole in the manifold too. The hole is supposed to be over sized to allow for differential thermal expansion between steel and aluminum.

Share this post


Link to post
Share on other sites
Neither "solution" addresses the real problem. An 8mm stud should be plenty strong to hold the manifold in place assuming there are no other underlying problems. The real problem is probably that the bolt is corroded due to water intrusion from a current or previously leaky thermostat housing and/or the manifold is warped...which was probably also caused or made worse by the leaky housing. I think people don't notice leaks there because it runs on the hot manifold and evaporates up quickly.

 

generally both of the outside bolts pop out, both are in 2 completely different locations as far as being exposed to the elements (and my thermostat housing has never leaked from my knowledge)

 

i think its more about thousands of heat cycles on the 2 outer bolts (of which hold the most pressure on the manifold) and the metal just become compromised, all of my stock exhaust bolts came out easily and had little corrosion

Share this post


Link to post
Share on other sites

Well, I don't know about "generally." I've owned 3 S30's and none of them had studs "pop out." Seize, yes, strip, yes, pop out, not yet. You are correct that heat cycles are causing the manifold to warp over time. My point is that there is more at play here, especially on #1, the one that is broken on the OP's car. After discussing the pitting around #1 exhaust port on my rebuilt head (shown below) with Dave Rebello, he stated that it was very common on L6's. Do you think this might have something to do with #1 exhaust stud failing? I think so.

 

img_1609.jpg

Share this post


Link to post
Share on other sites

img_1609.jpg

my head looked nothing like that, no pitting at all, no rust on what was left of the bolt

 

has anyone ever had one break off as they tried to remove their exhaust manni bolts? most of the stories you hear seem to be "looked at the manifold and the bolts were missing" alot more than "had a bolt/stud break on me"

Share this post


Link to post
Share on other sites

so there really is no other way but to just remove the bolt. i was alittle skeptic because i had to replace the thermostat/head gasket one time and im pretty sure some of that fluid curroded the bolt.

 

i actually like the idea of tig welding a screw driver to the bolt and backing it out.

 

i do have a question, what if i were to weld a bolt to the one thats already in there so that it sticks out about an inch and use a nut to tighten it down?? would this be worth it? thanks

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×