Threadlocker on external engine bolts

ToxicBill

Well-Known Member
I'm getting ready to put pieces back on my engine (intake/exhaust manifold, fuel rail, alternator, etc). Is there a recommendation to use or not use threadlocker?
 

ToxicBill

Well-Known Member
So, for the exhaust manifold, it appears that it would get too hot for threadlocker to remain effective.
 

Ross

Goblin Guru
I like to use anti-seize on all bolts, especially when they are in dissimilar metals like steel and aluminum. Exhaust bolts are exposed to high heat and tend to seize and gall more often.

I use thread locker if I have problems with bolts backing out, or if the manufacturer calls for it. Mostly prefer blue/medium strength thread locker, and use red thread locker very sparingly. Dirt motorcycles, RC cars, and bolts in high vibration areas are my usual suspects for thread locker.

Just my 2 cents, but I would like to hear other people's opinions.
 

Lonny

Administrator
Staff member
Proper torque will keep most bolts in.

Connecting rods are probably the most stressed bolts in an engine and they don't use thread locker.

A good rule of thumb is if GM used a thread locker you should. You usually can look at a bolt and see the remnants of a thread locking substance if it was used.
 

ToxicBill

Well-Known Member
Thanks for the replies. It did look like there was something in the bolts as I cleaned them but the information I saw seemed conflicting . . . Or GM used anti-sieze on the exhaust manifold studs. In any case, I put them back on dry and torqued them down to 10ft-lbs and will monitor then one I get this bad boy running.
 

Briann1177

Goblin Guru
I like to use anti-seize on all bolts, especially when they are in dissimilar metals like steel and aluminum. Exhaust bolts are exposed to high heat and tend to seize and gall more often.
How do you properly torque down bolts that have a "lubricant" applied? And yes, I understand anti-seize is not designed to be a lubricant, but it does have properties that reduce friction which could cause the bolt to be over torqued.
 

JBINTX

Goblin Guru
I have seen instructions for exhaust nuts and bolts call for a light film of oil. The heat will still get to them sooner or later and they will rust from the thermal stress cycling.
 

JBINTX

Goblin Guru
How do you properly torque down bolts that have a "lubricant" applied? And yes, I understand anti-seize is not designed to be a lubricant, but it does have properties that reduce friction which could cause the bolt to be over torqued.
In the transportation industry we had several torque values in suspension components for lubricated as well as non-lubricated. The lubricated values are higher and are actually more precise.
 

Karter2026

Goblin Guru
Proper torque will keep most bolts in.

Connecting rods are probably the most stressed bolts in an engine and they don't use thread locker.

A good rule of thumb is if GM used a thread locker you should. You usually can look at a bolt and see the remnants of a thread locking substance if it was used.
All true except I will argue some points on the if GM used it part. They put a yellow thread locker on brake caliper bolts. My first move is to the wire wheel to take that stuff off. put a dab of anti seize on and put it all back together. Never had a caliper bolt come loose.


How do you properly torque down bolts that have a "lubricant" applied? And yes, I understand anti-seize is not designed to be a lubricant, but it does have properties that reduce friction which could cause the bolt to be over torqued.
Over my years. I have read a lot specs that have said lubricate threads, install and torque.

Anti- seize is a must in my opinion on dissimilar metals. Also if you are in an area where they use a salt brine on the roads anti -seize is your best friend.
 

Lonny

Administrator
Staff member
All true except I will argue some points on the if GM used it part. They put a yellow thread locker on brake caliper bolts. My first move is to the wire wheel to take that stuff off. put a dab of anti seize on and put it all back together. Never had a caliper bolt come loose.
I think the reason car manufacturers place thread locker on certain bolts is not always that they may vibrate loose, it's there as a safety measure.

If they accidentally leave a bolt under torqued it will not work its way out.

Engine and transmission bolts, which see more thermal cycling and vibration than any other part of the car, rarely have thread locker.

Suspension components and brake components often have thread locker or locking nuts to prevent them from migrating if they are not properly torqued during installation.

They even put some type of blue thread locker on the little screw that attaches the brake light switch on the pedal box that causes everyone to brake the screw off.

Note: You can remove the brake switch screw by holding a lighter or soldering iron against the threads until it softens the thread locker.
 

PyroGuy923

Well-Known Member
They even put some type of blue thread locker on the little screw that attaches the brake light switch on the pedal box that causes everyone to brake the screw off.

Note: You can remove the brake switch screw by holding a lighter or soldering iron against the threads until it softens the thread locker.
Yup, snapped mine right off because I didn't know this.
 

WYGoblin

Well-Known Member
I broke mine but was able to unscrew it the opposite way by taking bolt through the switch like I was tightening it
 
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