Exhaust Man. Bolts Loosen Up

[hatcity]

2001 E-7 427

While back I replaced exhaust manifold. Lately been hearing typical chirp and check. Yep nuts are loose. tighten down and several days or weeks they are loose again.

Ideas why, how to fix, can I use Loc-tite or is heat too high.

Every thing else looks fine. Not a big deal to retighten weekly, but would like to know.

Thanks, Ed

[rhasler]

2001 E-7 427

While back I replaced exhaust manifold. Lately been hearing typical chirp and check. Yep nuts are loose. tighten down and several days or weeks they are loose again.

Ideas why, how to fix, can I use Loc-tite or is heat too high.

Every thing else looks fine. Not a big deal to retighten weekly, but would like to know.

Thanks, Ed

According to Mack exhaust manifold and turbo mounting hardware are one time use items. On your engine the studs are 616GC245M4. I will have to check the number for the nut as I can't remember it at the moment. There are several revisions to the hardware, mostly for the ASET AC engines. There is also a Multi-layer turbo gasket that replaces the standard gasket. On E-tech/ASET engines the fuel lines should also be replaced (again, this is also a one time use item) and tightened following a specific torque procedure to prevent fuel spraying onto the exhaust manifold which can result in "thermal events". I haven't heard of this being a real problem on the E-tech's, mostly on the ASET AC engine. I'll get the number for the nuts for you.

[hatcity]

Thanks for that. just a PIA to replace studs but not a big deal. Wonder why Mack parts didn't tell me this when I purcahsed manifold section. did get new bolts for turbo as center section bit the dust. Course they can't even tell upgrades avail. for truck. "Whats in the build sheet, is what I can give you"

[rhasler]

Thanks for that. just a PIA to replace studs but not a big deal. Wonder why Mack parts didn't tell me this when I purcahsed manifold section. did get new bolts for turbo as center section bit the dust. Course they can't even tell upgrades avail. for truck. "Whats in the build sheet, is what I can give you"

Sounds like my parts department. The part number nut for the manifold I would use is 142GC35M. It is a spiralock thread with a serrated flange. These nuts are silver in color instead of the originals which were copper colored. You might want to check your invoice and make sure that the manifold gaskets you bought were part number 573GB257A (this number may change also, I'm not sure). These can be identified by the steel ring around the port opening. The newest ASET AC hardware will also fit but will probably cost more and I'm not sure that it would really be of much benefit on your engine. I haven't seen this hardware configuration cause much trouble on ASET AI engine when tightened per procedure. I usually tighten in torque sequence in stages: start at 25 lb. ft, then go to 50, 75, and 100 lb ft. Studs should prtrude from the head 1.75" in order to avoid contacting the pushrods. This will be difficult to measure with the manifold installed. There are stud removers available to remove the studs. The ones I use are Mac tools, but I think they're available at NAPA or CARQuest too. They will save you hours of labor removing studs. When installing new studs put a dab of silicone on the threads of the stud where it goes into the head to prevent oil leaks (Mackpro68 posted about this a week or so back). Apply anti-sieze to the turbo studs where they thread into the manifold. Apply a light coat of engine oil to the threads, flanges, washers, and mating surfaces of the parts prior to assembly. Attached is the torque sequence as well as a cross sectional view of the manifold and cylinder head explaining why the studs should prtorude 1.75".

E-Tech Exhaust Manifold.pdf

[hatcity]

Sounds like my parts department. The part number nut for the manifold I would use is 142GC35M. It is a spiralock thread with a serrated flange. These nuts are silver in color instead of the originals which were copper colored. You might want to check your invoice and make sure that the manifold gaskets you bought were part number 573GB257A (this number may change also, I'm not sure). These can be identified by the steel ring around the port opening. The newest ASET AC hardware will also fit but will probably cost more and I'm not sure that it would really be of much benefit on your engine. I haven't seen this hardware configuration cause much trouble on ASET AI engine when tightened per procedure. I usually tighten in torque sequence in stages: start at 25 lb. ft, then go to 50, 75, and 100 lb ft. Studs should prtrude from the head 1.75" in order to avoid contacting the pushrods. This will be difficult to measure with the manifold installed. There are stud removers available to remove the studs. The ones I use are Mac tools, but I think they're available at NAPA or CARQuest too. They will save you hours of labor removing studs. When installing new studs put a dab of silicone on the threads of the stud where it goes into the head to prevent oil leaks (Mackpro68 posted about this a week or so back). Apply anti-sieze to the turbo studs where they thread into the manifold. Apply a light coat of engine oil to the threads, flanges, washers, and mating surfaces of the parts prior to assembly. Attached is the torque sequence as well as a cross sectional view of the manifold and cylinder head explaining why the studs should prtorude 1.75".

Thanks for the add'l info. Remember seeing Mackpro mention silicone if leaking. since they will be out, might as well do it, keep the motor clean

[Josephj_23]

What’s the torque spec for the bolts going from the turbo to the manifold on that ai370

[Onyx610]

30 ft/lbs I believe. I can get that for sure tomorrow. Im sure the job is done….

[Joey Mack]

10mm grade 10.9 is 50-55lbft.. jojo