Exhaust Manifold Newbie Question ...

[techboy]

So, I posted up in the B.S. section last week that I just purchased my first Quest and one of the issues with this car is that it has an exhuast leak at the manifold/turbo. I was looking at it closer the other day, and although I can't quite tell, I looks like someone did a hack job on the manifold flange b/c I can see some welding. I can't quite see whats going on until I take the turbo off, but my guess is that that is my leak. Anyway, I'm thinking it might just be best to replace the manifold with a new OEM one. I see the DAD's website sells one, but it's like 270 bucks. And there's a cracked one in the F/S section for 10 bucks. I can't find one anywhere else.

 

So ... the question ... for those of you who have been around ... is this typically a difficult part to find? Is the 270 from DAD worth it for a new one? Do most people go right to an aftermarket one? (I saw one on eBay with a external wastegate mount).

[dmyers151]

I'd avoid most eBay stuff.

 

Most aftermarket manifolds shift the turbo mounting position and then your exhaust won't line up.

 

$270 for a new one is a bit steep. If you know someone that's a good welder, a cracked manifold is fixable as long as it's not all thinned out around the crack. I've got (2) spare stock manifolds, both cracked. They aren't really hard to come by.

 

I'd look a little closer at your manifold before you make any assumptions. These manifolds are prone to flexing and warpage. They usually end up pulling the lower #4 cylinder stud outta the head. Your issue may lie here, in which case you don't need a new manifold. Any easy fix involving removal and plaining of the flange at a machine shop (~$30), and installing a helicoil into the head.

 

Remove the upper turbo heatshield, and making sure the exhaust is cool, start the car and feel around for leaks. Even if the manifold was cracked and repaired once, it's still probably savable.

Edited August 3, 2010 by dmyers151

[polarisman14]

I've got a good used one available for $65 shipped, no welding done to it (that's why you'll see many for sale that say "without cracks" or "repairable" etc.).

 

Welcome to the site.

[starquestG54B]

check your turbo for shaft play. u could just have leaking turbo seal

[BC_99]

every one I have seen taken off the cars have been cracked. even if they dont look like it. I have stuck 5 or 6 so far in the beadblaster to get all the old scale off and they were all cracked. I have welded up a few of them, and they are ok for awhile. but they will crack again. the ebay stuff will crack and like d said will relocate the turbo and the exhaust wont work without a custom downpipe. If you can find a used one that isnt cracked I would be surprised. I just bought a new stress relieved one from dad and will be having it ceramic coated before I install it. Hopefully this will help it last a bit longer.

 

BC_99

[techboy]

Well I obviously don't know if it's cracked or not b/c I haven't taken it off yet, but what I meant by "hack job" in my original post was I can tell looking at it that someone cut off the flange and welded it back on in a different position to account for the aftermarket turbo that is on the car, which I am eliminating. (going back to a stock turbo for now). Problem is they did a crappy job - looks like a "new welder in the back of his garage" job. So, I'd bet my next paycheck that's where the leak is. I'm working on the car Friday, so I'll figure out how bad the manifold is then. Maybe I'll throw up a pic and see what you guys think. I was trying to do my homework ahead of time b/c I think it's going to be a lost cause.

[Indiana]

If you bought a new one I'd suggest you don't waste your money on any coating of any kind. They all warped, every one of them. If they cracked that was another matter and I've only seen a few cracked ones and yes I've bead blasted them. You can get the layers of crap off and they look new again even the turbine housing. That manifold rust is several layers thick and its on the sealing surfaces of the turbine housing to the manifold and its why after these earlier engines with the DSMs they also switched to a multi-layered gasket for those surfaces too.

 

http://www.b2600turbo.com/images/IM002218.JPG

 

They knew this from the beginning and had the lame "fix" instead of replacing the part with a new design but that would have required further changes to the exhaust system. They bought some time with a layered gasket I'd guess they only cared until the warranty ran out. I' think you will end up having that new manifold machined flat again after its been heat cycled over about 15-20k miles that's when mine started to leak first.

 

http://www.b2600turbo.com/images/exhgasket.jpg

 

 

[Starfighterpilot]

Ya might want to take a look at this thread too. It has pictures of the problems that the guys are talking about and has some options for the exhaust manifolds.

 

http://starquest.i-x.net/viewtopic.php?t=924&postdays=0&postorder=asc&start=0

 

I believe that welding of crack(s) in the Starquest exhaust manifolds is a viable option. If you decide to reweld it make sure that the guy doing it uses the proper weld procedure for cast iron, ie. preparation of the weld joint (including drilling holes at each end of the crack and "V" notching the crack by grinding it out), uses the proper weld rod, and gets the manifold up to the proper temp that the manifold has to be preheated to before welding IAW the procedure, and the proper temperature cool down rates. It might cost ya about $150 for this type of welding but you will have a manifold weld joint that is stronger than the surrounding cast iron and won't crack again. Of course you will have to have the manifold mating (seating surfaces) re surfaced afterwards. To me $150 or there abouts is a heck of a lot cheaper than a relieved brandy new manifold.

 

Maybe some of you AWS certified welders can chime in here.

 

I would also drill out all the manifold's mounting to head stud holes to 27/64" and cut the webs. I have found that by using the Felpro exhaust manifold gasket, high temp, high pressure nuts and split lock washers they do not back off nor pull out the mounting studs from the head over time. BUT you have to retighten/torque 'em two or three times after each time the engine is run for about 1 hour after installation. You will find that they are loose the first two times you retighten 'em to about the TORQUE value due to the gasket compression. But after that the fasteners and gasket are tight as a drum. And Do Not do any high boosting until they are retightened for the third time (leaks) or over torque the mounting fasteners (pulled out studs now or later on).

 

This is just me , but I think that the Felpro exhaust manifold gasket is better than the MITSU OEM gasket, cuz: (1) being a porous material it somewhat expands and contracts to allow for the stud growth and contraction at the manifold to head joint during the initial and subsequent heat up cool down cycles without completely loosing it's seal (provided it's retorqued as noted above); (2) being a porous material it conforms to and seals any imperfections in the joint mating surfaces better: whereas the MITSU OEM one hardly compresses at all. Besides that, the Mitsu one will cut the crap out of you if you even look at it sideways when you're changing plugs or working on the turbo.

 

Another thing that I do is Never Seize all of the male fastener threads and gasket seating surfaces of the exhaust system before assembly. Which includes the heat shields' mounting bolts & spark plugs; MUCH easier to remove 'em later on.

 

For What It's Worth.

 

KEN

 

Edit: Right now the exhaust manifolds are relatively plentiful if you wanna "pay to play." But like a lot of Starquest parts, some time soon the supply will run out. Then wa'cha gonna do? I believe it's better to reweld what ya got or stock pile a couple of manifolds that are not cracked too bad for the future, modify 'em as I and PQ's link noted above and locate a welder who knows how to correctly weld cast iron.

 

Sorry Randy.

 

BTW - I modified my correctly welded exhaust manifold IAW PQ's post above and installed a Felpro gasket about 45K miles ago. NO LEAKS OR CRACKS since then. I thought that I recently had a cracked exhaust manifold on my way down to St Augustine FL from Tulsa OK, but it turned out to be that the turbo flange to exhaust manifold mounting flange fastener nuts backed off after about 35K miles. I got rid of the flat washers for that joint's OEM fastener assembly and installed split ring lock washers. I'll see how long those last. I wish that I can find a flat sheet of the Felpo gasket material so I can cut my own gasket with a ball peen hammer for that joint rather than using the Mitsu OEM Stainless Steel gasket.

Edited August 5, 2010 by Starfighterpilot

[techboy]

Well, I definitely confirmed today, someone cut off the flange, and rotated it 90 degrees to make the flange match up with the aftermarket turbo they put on. I doubt I'll be able to have it cut back off, and rewelded in the original OEM location due to how piss-poor it looks. So, I think I'm going to have to track one down, cracked or not, and go from there. When I actually take it off, I'll post up a pic so you guys can see what this person did.

[dmyers151]

Their not hard to come by, post up in the parts wanted section. I'm sure you'll find an affordable piece pretty quickly.