I am Jeff

If you had the option to have your headbolts replaced on your C63, would you have it replaced even if your car has no issues? I would like to hear the pros and cons of having it replaced. I understand that there are risks with opening a can of worms by touching a motor with no issues.

Your input would be greatly appreciated.

mdgrwl

Everyone has the option to replace headbolts. I would wager 99% of people are not replacing them if they don't have an issue. Why are you so paranoid?

jellis102.com

I did mine after the first low coolant message, was it necessary? I don't know but I don't have to worry about it at all now. PLUS, it's much cheaper to replace it prior to damage.

ZephyrAMG

Great question. I think you can do a bolt at a time without even removing engine. I am conserving the same thing just to have peace of mind...

I am Jeff

I have the option to replace them free of charge. I don't really have any issues with mine, other than oil consumption. I was offered the option to have them replaced, but I'm just worried about opening a trouble free motor, in an attempt to resolve a potential issue.

Would you do it?

Sincity

AFAIK, you don't need to remove the engine to replace head bolts. I think you meant the head(s).

Merc63

You don't need to open the engine. Replace one at a time.

If you plan on keeping the car I'd replace them.

It will be an excellent option for resale too.

I am Jeff

Thanks for the response! I do intend to keep the car, but was just worried about any potential issues that may arise. My friend intends to replace a bunch of parts once he opens it up (gaskets, headbolts, etc...)

abcut973

I would do it too knowing it is free of charge and that it will give you piece of mind.
Now you are saying your friend will be doing it.... how experienced is he?
I would rather be picky about the tech who will work on my engine for this job.

I am Jeff

He's a tech that works on these motors on a daily basis.

BiturboSF

How much would replacing your head bolts cost roughly? My car is a 2009 with 38k miles, typically at the mileage when they would go.

DuaneC63

Hella yea. Read the sticky in this forum. Replace everything with the updated parts including the lifters. Everything is one time use torque to yield any way. Hydrolock equals a blown motor.

DuaneC63

The headbolts can fail anytime. Dealer has told me even low mile cars (less than 10k have failed). Additionally anyone that does any research on the 6.3 motor cars is going to come across this potential failure and either not buy or low ball you. MBZ will not replace them until they fail, so get a long warranty.

DuaneC63

Merc,
Not to be a stickler, but the head bolts are torque to yield and many of them are under the cams. Hence replacing one at a time is not a viable solution. If you replace one you have to replace them all including pulling the heads as the head gaskets are compromised when all the head bolts are taken out. I wish there was a short cut, but there isn't.

Merc63

Sorry but this is totally incorrect.

Search for my stage 3 and head bolt replacement thread where I switched each bolt to a stud one by one without removing the head.


The head gasket will not at all be compromised. There is no force on the head with the engine not running. All other 9 bolts that remain in while one is removed is well over 150,000psi clamping force.

Simply remove cams and replace one at a time.

RawBenz

Hi just a quick question, what are the symptoms of a head bolt issue and what can cause it?

builthatch

there is a sticky at the top of this sub forum about the head bolt issues, check that out.

I am Jeff

Thanks Duane. I was thinking the same thing, if done properly, the risks are far outweighed by the rewards. What are the parts that should be replaced? Bolts, gaskets, lifters. Anything else?

Ingenieur

if it was being done for free by a dealer and by a tech who had done it before and had access to MB techinical supprt services, yes

by some guy is a garage, no


from what I can see it can be done one bolt at a time but the cams must be removed
a fairly complicated procedure

if you go that far might as well remove the head and replace the gaskets and torque the bolts per spec

Ingenieur

first you say there is NO force on the head
then you say there is 150,000 lb (force), btw NOT psi which is a unit force/area
(probably closer to 140kip, but who's counting, lol)

to get psi = 150,000 lb / area in^2 of the head
head area ~ 250 in^2 ~ 600 psi

releasing 1 bolt may distort the head and gasket or stretch the other bolts (even the ones just installed)
better to release and apply in sequence and in stages
will it lead to early failure? who knows, probably not

motoman

According to gasket mfgrs many hi po head gaskets are made with spring steel . When running, the head , gasket and headbolts look like a trampoline. Then there's the surface "bite" of the gasket on head/block. The diesel hot rodder blogs I read mostly frown on one at a time.

I want to believe, I want to believe. But seems like the head off, lifters, TTY head bolts are the way. But if the cams could stay in I would try it.

Sure wish we could get some more input on headbolt logos...You know, the dream that only one vendor produced a few headbolts and only they are bad. Finally, none of our engines contain those headbolts.

Merc63

Look up clamping force of a bolt.

Clearly talking about force from a running engine.

Sure replacing the gasket and removing the head is ideal in a perfect world. Is it necessary, doubt it.

Running stage 3 power through mine for 10,000 hard km. you want to tear your heads off and remove the engine to replace, go hard.

Ingenieur

I don't have to google it, I have a bit of experience with fasteners...it's the force between 2 mating surfaces generated by the torquing/tensioning/stretching of the fasteners clamping them together...the tension stored in the bolt is its source, not the machine/engine...

it is static and does not matter whether the engine is running or not
it is what prevents combustion from blowing the head off

the average (not peak or impulse) force it resists IS generated when the engine is running and is:
~ comp ratio x atm pressure x vol eff x piston area
~ 11.3 x 14.7 x 1.03 (estimate at peak) x 12.6 ~ 2200 lb
dimensional analysis = unitless x lb / sq in x unitless x sq in = lb (force)

side note bearing throw is ~ 2.4 in or 0.2 ft
torque = F x r = 2200 lb x 0.2 ft ~ 440 lb ft of torque

the actual clamping force is ~140,000 lb or 14,000 per bolt
assume 2.5 bolt per cylinder (10 bolt/ 4 cylinder) so each cylinder has ~ 35,000 lb of restraining force for 2200 lb of applied force

if you 1/2 *** something you get 1/2 assed results
as I said, probably makes no difference with the safety factors involved

if I were to do it:
release tension in ALL bolts per the mfgs removal sequence (1-2 turns should do it)
then replace 1 bolt at a time in the mfgs recommended install sequence
apply an extra 30 to 45 deg of final torque angle to compensate for the previously compressed head gasket

but I would probably pay someone to do it right if I were actually doing it...but that's just me

Merc63

Sweet math lesson

Ingenieur

you're welcome

but it's actually an 'engineering lesson', math is the language of engineering (and physics)