Exhaust Manifold Stud Oil Leak

[1991ZR1]

I'm trying to fix the oil leak from the driver side exhaust manifold stud. I have all the bolts loose to remove the manifold but if I remove it, I'm not sure how to get the front bolt back in because of working space. The manual simply says to install the bolts. Are there any tricks to doing this? Maybe removing the power steering hoses will allow you to get your hand in from the front?

The manual also says to use Loctite 620 when you reinstall the stud. Is this the best thing to use? If you can't find Loctite 620, what's the next best thing to use?

Any advice will be appreciated.

[1991ZR1]

Thanks for the link. It seems that RTV is a popular substitute.

I don't think I will be able to work between the tubes and get the stud off and reinstall it but I'll give it a try. I didn't mention earlier but i have the stock manifolds. I still need to know how to reinstall the front bolt on the manifold in case I can't reinstall the stud without removing the manifold.

[secondchance]

Thanks for the link. It seems that RTV is a popular substitute.

I don't think I will be able to work between the tubes and get the stud off and reinstall it but I'll give it a try. I didn't mention earlier but i have the stock manifolds. I still need to know how to reinstall the front bolt on the manifold in case I can't reinstall the stud without removing the manifold.

It has been awhile since I installed my header w/ the WAZOO gang and can't remember how diffiult the particular bolt was. Actually on later cars first and last bolt holes are substituted with stubs on the block eliminating bolts.
I presume you removed the plastic liner?

[1991ZR1]

I'm not sure what plastic liner you're talking about. If you're talking about the wheelhouse panels, yes I removed them.

Now that you mention studs, I could replace the bolts with studs.

I'm also thinking the manifold flange could be slotted to allow the stud or bolt to be in place before installing the manifold.

Thanks for the ideas.

[Blue Flame Restorations]

I'm not sure what plastic liner you're talking about. If you're talking about the wheelhouse panels, yes I removed them.

Now that you mention studs, I could replace the bolts with studs.

I'm also thinking the manifold flange could be slotted to allow the stud or bolt to be in place before installing the manifold.

Thanks for the ideas.


This is exactly why I like this group of great guys!!!:handshak:

[1991ZR1]

Looks like I have a bigger problem. The problem is that I don't know where the oil is coming from. I removed the exhaust manifold and took out the center stud. When I removed the stud, the threads were dry. No oil. Everything is a mess so I can't tell where the oil is coming from. The only thing above the exhaust Manifold is the cam cover but that does not appear to be leaking. I cleaned things up a little and I'm going to have to reinstall the manifold and see if there is still a leak. If it still leaks, I have to remove the manifold again and look for fresh oil.

[Z51JEFF]

A leaky dipstick tube seal will cause a leak.

[scottfab]

Looks like I have a bigger problem. The problem is that I don't know where the oil is coming from. I removed the exhaust manifold and took out the center stud. When I removed the stud, the threads were dry. No oil. Everything is a mess so I can't tell where the oil is coming from. The only thing above the exhaust Manifold is the cam cover but that does not appear to be leaking. I cleaned things up a little and I'm going to have to reinstall the manifold and see if there is still a leak. If it still leaks, I have to remove the manifold again and look for fresh oil.

If not the stud then the usual suspects are the Oil Pressure Sender and the Oil Level sensor if your MY has one. The leak can run along the side of the engine and gets to the bottom.

Best detection is a complete cleaning of all oil.
Then allow to dry and then a drive.
If it's still there it's then easier to detect.
Good luck.

[Pete]

Guys he said "driver side"

Check cam sensor.
Also one of the 3 power steering mounting screws goes thru needs RTV,it's the one furthest left just take it off RTV it and reinstall.

Also it might give you some more working room if you take motor mount nut off and jack up/raise motor a bit.

Pete

[1991ZR1]

I never thought about removing the motor mount nut and raising the engine. Or checking the cam sensor. Is that the thing just below the cam cover? Funny that it is the thing that was in my way when working on the manifold.

I ended up getting the front bolt on by using a shorter bolt without the spacer. Because of the tight space I still couldn't get a regular socket and ratchet on the bolt. I got a 12mm 1/4" drive socket that has a hex on the back end from Lowes and used a gear wrench with that socket. That setup is shorter than a regular socket and ratchet.

Anyone working on the manifold bolts needs to be careful not to drop the bolt into the manifold or the area next to the steering coupler. I spent quite a bit of time trying to fish them out with a magnet before I figured out that they are not magnetic.

[scottfab]

...snip...
Anyone working on the manifold bolts needs to be careful not to drop the bolt into the manifold or the area next to the steering coupler. I spent quite a bit of time trying to fish them out with a magnet before I figured out that they are not magnetic.

Ah yes, the dreaded "where did it go"?
I have one that dropped into a hole in the frame rail.
At least it doesn't rattle in there.

A thorough engine cleaning is the best for locating leaks.
Else shotgunning all fasteners is next I suppose.

[Corbusa]

" Anyone working on the manifold bolts needs to be careful not to drop the bolt into the manifold or the area next to the steering coupler. I spent quite a bit of time trying to fish them out with a magnet before I figured out that they are not magnetic. "
Thanks for that info.. !!! That would be a B....

[tpr60]

Bin there done that!!! Stuff shop rags in the ex manifolds for that pain in the butt relief.

[Fully Vetted]

Stuff shop rags in the ex manifolds for that pain in the butt relief.

You know they sell ointment for that...

[Cal55]

I'm just curious if you ever found the leak? I've developed a leak too on the passenger side. It seems very minor I only notice it after a cold start up, oil starts smoking off the exhaust manifold after a few minutes, after driving the car I don't notice any smoke at all.

[1991ZR1]

I haven't driven the car since January but this is how things went.

I put the driver side center stud back in with RTV sealant. If I had to do this job again, I think it could be done without removing the manifold. I would try backing all the bolts out and move the manifold away from the head as I remove the center nut. That would give more working space.

After I finished the driver side, I worked on the passenger side. It was much easier. I did not have to remove the manifold or any of the bolts. I did remove the check valve from the AIR tubes though.

After I finished both sides, I started up the car and let it run. After it warmed up, both sides started smoking. I just let it run and eventually all the smoking stopped.

Last week I started up the car again and let it run. There was no smoke from the driver side and a very light smoke from the passenger side which stopped after a short time.

I would have to assume there was some residual oil and the RTV on the studs repaired the problem.

[Cal55]

Thanks for the update, I appreciate it. I have to find out where my leak is coming from, it's very minimal right now. It was fine last summer, I noticed it when I started the car this spring. I'll have to jack up the car and see if I can spot the leak or take it in for an oil change and look for it when it's on a lift.
Joe

[SoCalZR1]

It may seem counter intuitive but I would also check the oil pan bolts. I went through all the usual culprits and did not find the source of my leak. The leak included oil on the driveway and light smoke visible with the associated smell.

Ultimately it turned out to be the front 6 bolts that were the cause of the leak. You will need to remove a couple of brackets that are in the way, and yes you can remove them temporarily to gain access. So far I have had no leaking simply from re-torquing them. If it ever comes back I will swap the oil pan gasket.

Hope that helps.

Mike

90 #961

[Cal55]

Thanks Mike,
That's good to know, I hope my fix is that easy. I probably won't be able to look at it until maybe next weekend. I don't see any oil on the garage floor so it must be a pretty minor leak.
Take Care,
Joe

[LGAFF]

Cam sensors can leak also from D/S

[Cal55]

I haven't driven the car since January but this is how things went.

I put the driver side center stud back in with RTV sealant. If I had to do this job again, I think it could be done without removing the manifold. I would try backing all the bolts out and move the manifold away from the head as I remove the center nut. That would give more working space.

After I finished the driver side, I worked on the passenger side. It was much easier. I did not have to remove the manifold or any of the bolts. I did remove the check valve from the AIR tubes though.

After I finished both sides, I started up the car and let it run. After it warmed up, both sides started smoking. I just let it run and eventually all the smoking stopped.

Last week I started up the car again and let it run. There was no smoke from the driver side and a very light smoke from the passenger side which stopped after a short time.

I would have to assume there was some residual oil and the RTV on the studs repaired the problem.

I looked at the passenger side manifold stud and there is oil residue on it and the manifold. How did you remove the check valve from the AIR tube and the stud? It's a tight fit getting a wrench in there. I was able to get an open wrench in there but didn't have enough leverage to even loosen it. I also noticed some frayed wiring going to the front shock to change the ride mode, but that's another issue.
Any help is appreciated.
Thanks,
Joe

[Cal55]

Cam sensors can leak also from D/S

Thanks for the reply, I'll keep that in mind. My leak right now is on the passenger side, leaking from the exhaust manifold stud and the grommet on top possibly.
Joe

[1991ZR1]

I don't remember which, but it was either an open end wrench or a short adjustable wrench. Most likely it as the open end wrench for the leverage at least to get it loose.

[Cal55]

I don't remember which, but it was either an open end wrench or a short adjustable wrench. Most likely it as the open end wrench for the leverage at least to get it loose.

Thanks, I guess I'll have to put another nut on the stud to lock the other one in place to remove the stud. If anyone has any tricks or suggestions in doing this I'd appreciate hearing them.
Joe

[LGAFF]

Sometimes if you are lucky the stud will back out when you turn the nut....I was not so lucky...be patient.

[Cal55]

Sometimes if you are lucky the stud will back out when you turn the nut....I was not so lucky...be patient.

That would be nice! I didn't work on it today, hopefully next weekend. Thanks for the reply!
Joe

[5ABI VT]

I'm curious what do the manifold bolts look like? I'm doing a hurst and beam plates and took a peek up there.. On the rear most bolts there is one missing.. And in inside what looks like a bolt hole on the manifold I can see a flat head screw 'head' of a smaller bolt...

[1991ZR1]

I'm curious what do the manifold bolts look like? I'm doing a hurst and beam plates and took a peek up there.. On the rear most bolts there is one missing.. And in inside what looks like a bolt hole on the manifold I can see a flat head screw 'head' of a smaller bolt...

The factory did not put bolts in all of the holes. The bolts don't look like anything special but they are non-magnetic. They go through a short spacer tube between the bolt head and the exhaust flange.

I don't know what you mean by inside.