keithw1975

I had an ATS 3 piece exhaust manifold put on my truck a while back after the factory one cracked. Ever since then the bolts, with lock washers, keep backing out ever 3 or 4 months. Any suggestions? Will locktite withstand the temperature?

Keith

DetroitDiesel71

I would stay away from the locktight, go to mcmaster carr or such and order some lockwire bolts. We use them on the boat engines for bolts on the exhaust that tend to back out. Don't know if they called that exactly, but the bolt head has a machined hole to run lock wire through it. Aircraft engines use tons of them.

PChouinard

Are the lockwashers good? They can loose thier locking capabilities after awhile. Are the socket head screws backing out or just the original bolts?

keithw1975

They have backed out since they were installed. A diesel shop installed the manifold and they used allen head bolts. Two of them fell out before I caught them so I replaced them with some regular bolts and more lock washers but all of them are backing out.

Marine

Did you call ATS? What do they suggest? Did you put anti-seize lube on them?

RowJ

Aircraft type bolts with saftey wire through the heads would hold them well!

RJ

PChouinard

Good point, If they were put in dry and torqued with out lube, you may have gotten a false torque on the threads. Back them out one at a time and apply some molydisufide antiseize and retourque. Hopefully someone didn't run e'm till they smoked then gave em another half turn. It's a misconception that manifold bolts need to be put in with a breakerbar and half-inch-drive tools...

keithw1975

I really have no idea weather or not they used anti-seize. The diesel shop that did the work was pretty slip shod in my opinion. They left the tube running to the heater core just hanging and after looking at the ATS website I see that there is a bracket they never put on which is to support it.

What is the proper torque for the bolts? The bolts do seem to turn freely. I have turned them with my finger until snug and it felt smooth.

Some of them are a real nightmare to get to with the tools I have.

Keith

PChouinard

I have the ATS manifold and the bracket that came with mine is on my work bench. The hose doesn't come near the bracket at all. Tate, a registered user, said he bent the bracket on his hose to fit. I'm going with a custom mount when time is available. Back to your bolts. Go get som molydisulfide and rent or borrow a small torque wrench capable of 32 foot pounds or 384 inch pounds, they're both the same. Back them out, lube the threads and torque them in. By the way. 32ft/lb and 384 in/lb are the specs..

Marine

Try the anti seize.

dodgezilla04

just drill your own bolts for lockwire. no need to spend the money on them. on my B series in the cranes, the exhaust manifold bolts have a tab washer on each one that is bent down to the manifold and up on a bolt flat. never gets loose. i can look in the parts manual tomorrow at work if you want. just shoot me a PM so i remember

PourinDiesel

Good advice here. Use anti seize and take the torque up to around 40 ft lbs.

Tate

I never used antiseize on mine, and they are still good and tight. Just used an allen wrench with a box end on it for a bit more leverage. I think drilling the bolts and wiring them would be the best way. Cummins also has the lock tabs for the original bolts to keep them from backing out.

RAFTEN

Wire them otherwise they will keep backing out.

RustyJC

The problem is that, if you torque these bolts cold to the yield point, they will deform permanently (in plastic as opposed to elastic deformation) when the manifold gets hot and grows. Then, when everything cools off, the bolts are loose - they've lost their prestress and clamp loading.

Lockwire or lock tabs will keep the bolts from turning, but they'll still be loose after a thermal cycle.

Two common approaches are:

1. Use long bolts and spacers (see the factory manifold), and don't torque to yield - that keeps the bolts from being overstressed when the manifold is hot.

2. Use the correct stack of Belleville washers under the bolt/nut to allow for expansion and contraction of the manifold without overstressing the fastener.

Rusty