How would you repair broken manifold bolts on a Cat 953 3204 engine?

Let us know in the future how it works out. Not sure grade 8 and studs would be my choice but then I have a Chevy 5.3 and it routinely breaks drivers front top and passengers back bottom OEM exhaust manifold bolts. That why I have the Doorman exhaust bolt bracket that bolts to the extra head holes handy.

I also used galvanized nuts which dont seem to have as good or as strong of thread as the harder grade 8 nuts do. Click to expand... I would not use galvanized anything in that location. Do yourself a favor and replace all with grade 8 The reason for grade 8 hardware is if they rust, most cases they can still be removed, they can be torqued higher and the exhaust heat will cause issues holding

I used high temp anti seize on all exhaust fixtures, the paste will burn, but will a fine coating. I used hardened flat washers, stainless fasteners , cat fasteners etc , pay me now or pay me later. Always thinking of the next guy that has to take it apart.

Screw that, I tried SS a few times over the years, a couple on Marine and they break faster than anything. The Nickel Anti Sieze, I slobber on, like someone else is paying for it. Have good luck with grade 5.

Georgia Iron said: Got it all back together and started back up. View attachment 354167 I went down to Cat and sat down with a salesman and looked over the information he had including the TMs and service manual. I could not find any information on which direction the manifold is supposed to go. Cat did update the small bolts on the outside mounting holes. Maybe 3/8s x 1". Guess how much they are each. $23.00 per bolt. I used 20 grade 8 bolts and made my own studs. I used lock washers on the outside mounting bolts and the lock tabs on the 4 inside bolts. I am not sure if the lock washer is a good idea or not. Cat uses the locking tabs and thats it. I also used galvanized nuts which dont seem to have as good or as strong of thread as the harder grade 8 nuts do. They seemed to stretch a little more. I am going to run it awhile and check the hardware for issues. I would imagine that you could spend close to $200.00 just for the Cat hardware. Hopefully I dont need to buy twice and cry twice.... On the warm up run no leaking was noticed. Online some guys say these nord lock washers are the best bet. I might go ahead and order some and swap them out. Bolt Depot - Nord-Lock® washers, Delta protekt® plated steel, 3/8" boltdepot.com Click to expand... The correct way to mount the manifold on the 3204 is shown in the parts book, it's with the small exhaust hole to the fan, you do have a riser between the manifold and the turbo so it will possibly make little difference, how you had the manifolds in the picture together was the correct position.

My thoughts in this day of every one having a phone. A couple of pictures before you tear it down would sure make a lot of conversation unnecessary

pittsburgh cat man said: My thoughts in this day of every one having a phone. A couple of pictures before you tear it down would sure make a lot of conversation unnecessary. Click to expand... As TC said. It might have been installed incorrectly previously. You can't tell anything about this manifold's orientation from the outside. But I agree take pictures before your fingers are too dirty to touch the phone.

I've had good success with a TIG welder. It requires good access, can't do it wedged up in a very bad place. Takes a bit of patience. Clean the broken end all you can. Might be 1/2" below flush. Precise very short arc. At first it'll be near impossible to get filler into the puddle. Be satisfied if you can only get a tiny dab of 1/16" filler. Repeat. As it comes up flush, it gets easier to focus arc & dab filler. Once flush, build a ball above flush. Drop a washer over the ball, then a nut. Weld through the hole in the nut to secure the nut to the ball. Find something to do for ten minutes, like starting the process on another broken bolt, let that one cool. If you don't mind smoke, a bit of oil might be helpful. When EVERYTHING is room temperature cool, use a flat open end wrench, turn it both directions very gently. Might turn it 200 times each direction before you detect a slight slip in the thread, you have won! Might still break it off before it loosens, but next round you will succeed.

Never put Spring Washers on a manifold location, never use Stainless Steel, never use Galv' coated anything, stick to 8.8 grade fasteners Graphite coated if possible, the 3204 has locking tabs list in the parts or just use top grade thick washers.

tctractors said: Never put Spring Washers on a manifold location, never use Stainless Steel, never use Galv' coated anything, stick to 8.8 grade fasteners Graphite coated if possible, the 3204 has locking tabs list in the parts or just use top grade thick washers. Click to expand... Nickel anti-seize is what I have put on them, but go a bit lower on the torque as per any never seize. Yes never use any spring lock washeers as they will break in time from the heat and then it is a loose connection. Thick hardened washers is the way to go. Simon C

Curious if studs are better than bolts on exhaust manifolds? Also is one less likely to put up a fight to remove if needed?

Welder Dave said: Curious if studs are better than bolts on exhaust manifolds? Also is one less likely to put up a fight to remove if needed? Click to expand... A lot of old engines used double ended studs. Might be 3/8 or 7/16 coarse thread in the block, then 3/4" wasn't threaded. Other end was fine thread shouldered downa size. Some had brass nuts. Logic was break off the smaller end, you could still get the manifold off, giving access to the protruding stud with vice grips, or welding a nut. Impatience has broken more manifold bolts than rust. Penetrating oil & a LOT of wiggling back & forth work much of the time. I've seen plenty of engines manufactured with stepped down studs, replaced with bolts. Many of these bolts weren't high grade even.

Welder Dave said: Curious if studs are better than bolts on exhaust manifolds? Also is one less likely to put up a fight to remove if needed? Click to expand... You will find that lots of companies used studs for a reason. The Underside of the thick washer to the face of the head is the stretch zone of the bolt. All of the stud that is within the head is not in the stretch loan. If there is not enough stretch zone from the cylinder head to the underside of the thick washer held in by the nut, the connection will break unless it is engineered with over size strength fasteners. A bolt with regular threads that goes into the cylinder head has very little thread sticking outside the head so very short stretch zone. That is why they break along with heat and fatigue. Simon C

CAT engines since the earliest days used stud, nut and washer clamping on manifolds, this would be in 2 size formats 3/8" and 1/2" UNC that always seemed to cope with the task, the problem with failed studs can really be blamed on poor care and service, bolts looking nearing their end of service should be replaced in timely fashion so no or little drilling out is needed.

tctractors said: CAT engines since the earliest days used stud, nut and washer clamping on manifolds, this would be in 2 size formats 3/8" and 1/2" UNC that always seemed to cope with the task, the problem with failed studs can really be blamed on poor care and service, bolts looking nearing their end of service should be replaced in timely fashion so no or little drilling out is needed. Click to expand... Seen too many with half the stud gone and still being used . then they wonder why they broke. Simon C

On another subject; GM V8 gas engines are troublesome. Exhaust manifold gaskets don't last. I can't say specifically which engines, my experience is the 6.0. Every other year I have to replace each gasket. GM uses some treated bolt coppery in color, their torque specification is barely more than finger tight. If access were easy it'd take an hour to replace the gasket. In a van, the first hour is used removing enough components to find the engine. Siezed studs aren't a problem, getting a wrench on a manifold stud is superhuman! By designing frequent failure into the gasket, manifold bolts don't have time to freeze.

I replaced a cracked exhaust manifold on an old Chrysler industrial engine with no problems at all. Maybe I got lucky?

Ha, this newer stuff, with soon to be obsolete V-8 engines, have no room to do anything. My brother has an overhead creeper that I occasionally use but hate. To get at the exhaust manifold bolts, I have to take the tire off, take out the inner fender and I can see part of it. Between bending pushrods and collapsing AFM lifters, my new to me trucks manifolds have been off 5 times, in 7 months and it still had 3 freshly broken exhaust manifold bolts. Then my brother convinced me to stop screwing around and pay the 23 dollars a piece from GM. Hopefully, they stay in one pice. The nice thing is, unless it’s making noise, outta sight, it’s outta mind and you really can’t see them. Unless, like when I bought the Doorman clamp, after finding one of the broken bolt heads, on the shop floor.