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JAM
01-12-2013, 11:36 AM
So I been putting off doing my glow plugs cause of all the horror stories of getting stripped out or breaking of in the head. Well it hit close to 60 degrees in Michigan yesterday so I figured I'd give it a shot. I first sprayed pb blaster than went for a drive to heat her up. All gp's came out pretty easy except for the second one from the front of the engine. Had to do the back and forth thing with the ratchet about 30 times with more pb blaster than it came out easy. I also changed out the gp module. My reason for doing the change is cause of hard starts when its real cold out and my check engine light would come on.
Got it all done in a couple hours and no more check engine light and seems the gp light goes out quicker than normal. I used Bosch gp's from Europarts along with there gp module. Heres a pic of the old ones. Dont know if they are the stock ones which would have 225k miles on them or not.
Also, I did not torque them to spec cause I dont own the tool. I only have the huge inch pd one. I just tightened them pretty snug with anti sieze. How important is it to torque them properly?
http://i267.photobucket.com/albums/ii288/jamstoyz/photo_zpsa0a90a52.jpg

Aqua Puttana
01-12-2013, 12:38 PM
...How important is it to torque them properly?
...
Glad to hear that it went well for you. I had one that needed a bunch of in and out turning also.

My opinion. This may be one of the most important jobs to use a torque wrench on.

Reasons...

Overtighten and you can strip or jam the glow plug into place to set up future removal issues.

Too loose and the seat seal down in the head won't properly seat.

A good mechanic with a good touch may get it right, but the torque spec is pretty light so it is pretty easy to overdo. FWIW. vic

tr4dude
01-12-2013, 03:00 PM
i run them in by hand then tighten them till they stop with the ratchet till they stop with light tension then give them 1\8 turn, no problems so far.

bc339
01-12-2013, 03:15 PM
What vic said, plus anti-seize will reduce the torque value because you have reduced the coefficient of friction. The values in the manual do not specify using anti-seize, so it should be considered the dry torque value. Reducing by 20% will be safe. The GP torque value is 115 in/lbs or 9.58 ft/lbs or 12 N-m. Subtract 20% is only 23 in/lbs, 1.9 ft/lbs or 2.4 N-m.

A decent torque wrench will set you back less than $100.00., more than worth the investment considering the possible consequences, plus a good tool for future jobs.

Bruce

autostaretx
01-12-2013, 07:09 PM
The GP torque value is 115 in/lbs or 9.58 ft/lbs or 12 N-m. Subtract 20% is only 23 in/lbs, 1.9 ft/lbs or 2.4 N-m.

Huh? 20% less than 9.58 ft/lbs is not 1.9 ft/lbs, it's 7.664 (to carry it out to ridiculous decimal places).

I think you quoted the 20% difference, not the 80% result.

So try 92 in/lb, 7.7 ft/lb, 9.6 N-m

--dick

bc339
01-12-2013, 10:54 PM
Yes, Dick you are correct - that is the difference. Sorry, I was in a rush to get out the door and enjoy the 80 degree weather.

Bruce

JAM
01-14-2013, 10:22 AM
Thanks everyone. Knowing ft pds helps cause I have a pretty nice wrench for that.

Toothman
01-14-2013, 12:00 PM
So I been putting off doing my glow plugs cause of all the horror stories of getting stripped out or breaking of in the head. Well it hit close to 60 degrees in Michigan yesterday so I figured I'd give it a shot. I first sprayed pb blaster than went for a drive to heat her up. All gp's came out pretty easy except for the second one from the front of the engine. Had to do the back and forth thing with the ratchet about 30 times with more pb blaster than it came out easy. I also changed out the gp module. My reason for doing the change is cause of hard starts when its real cold out and my check engine light would come on.
Got it all done in a couple hours and no more check engine light and seems the gp light goes out quicker than normal. I used Bosch gp's from Europarts along with there gp module. Heres a pic of the old ones. Dont know if they are the stock ones which would have 225k miles on them or not.
Also, I did not torque them to spec cause I dont own the tool. I only have the huge inch pd one. I just tightened them pretty snug with anti sieze. How important is it to torque them properly?
http://i267.photobucket.com/albums/ii288/jamstoyz/photo_zpsa0a90a52.jpg

Was wondering if you had any trouble getting the wire harness caps off the plugs. Did you use the "Hazet " plyers? Do you know of any other trick to get the caps off without the hazet plyers? I can't seem to pop mine off without fear of breaking them. I'm squeezing the sides of the cap with a pair of needle nose while trying to pop it off with a string looped around it but no success.

Boater
01-14-2013, 12:15 PM
Thanks everyone. Knowing ft pds helps cause I have a pretty nice wrench for that.

When in doubt try http://www.onlineconversion.com/ to convert torques into numbers you can work with, or any other units that don't make sense.

ishwashgus
05-08-2017, 01:18 PM
I doubt thread lubricant is a factor when torqueing the glow plug. As you tighten the glow plug to the point that it no longer turns, the coefficient of friction drops out of the equation. Just torque the darn thing to where it gets tight and don't worry about it. If you are even somewhat experienced as a shade-tree mechanic and have no history of twisting bolts in two; that is, you are not ham-handed, you should be able to just trust your feel of things. You don't need no stanking inch pound torque wrench, imho...grin...

Goofy foot
05-08-2017, 06:29 PM
Jam, it would be interesting to know the resistance values of the old plugs if they indeed went 225k. I'd open up the module and take a look at the copper fuse links just for reference at that mileage. Keep it for a spare just in case .

rollerbearing
05-08-2017, 07:33 PM
I know nothing about the Sprinter glow modules, but the ancient MB 300D and 240D modules tended to fail often due to solder cracks on the PCB (particularly around the larger and heavier components like relays). A bit of soldering and some wire frequently gave a good working spare.

Patrick of M
05-09-2017, 01:12 AM
Don't agree that "feel" is good enough for low torque items. "Feel" is fine if you have experience with higher torque values. But I have a little bitty in/lbs torque wrench and it is very hard for me to feel the difference between 7 and 10 in/lbs, and I've been wrenching for longer than I care to admit.

ptheland
05-09-2017, 01:39 AM
Don't agree that "feel" is good enough for low torque items. "Feel" is fine if you have experience with higher torque values. But I have a little bitty in/lbs torque wrench and it is very hard for me to feel the difference between 7 and 10 in/lbs, and I've been wrenching for longer than I care to admit.

I have to wonder if there is any practical difference between 7 and 10 in/lbs.

I would guess that many of these lower torque (and even some higher torque) specifications are there mainly for the original assembly process. Engineers for the pieces to be attached have to specify a torque so that the engineers who set up the assembly robots know what torque setting to program into the robot.

There are many places where torque specs are quite necessary - the precision tolerances in an engine or transmission or differential are a few such places. And yes, some of those fasteners could be specified in small inch pounds (or probably in fractional or single digit newton-meters).

I was sure that MB had gone overboard in publishing torque settings when they published one for the battery cover on one of their diagnostic adapters (probably the C3 or C4 unit, as those are the ones I researched) as part of the procedure to change its AA (or perhaps C) batteries. I'm sure you don't want to crack the cover or strip the plastic threads by over torquing. But if you've successfully changed a few batteries in kids' toys, you have a properly calibrated elbow (or wrist) for the job.

Patrick of M
05-09-2017, 02:41 AM
Low torque specs are for small diameter bolts in soft metals and other special considerations. An example is the wee bolts that hold the valve body in the nag1. I for one would not want to strip one of those, and yes I could probably "feel" the right torque not to strip them, but for whatever reason the spec on those is much lower than I would have "feel" torqued them. Some things seem silly to me, but buying a $100 dollar torque wrench that should last a lifetime with care, and then being able to torque everything to spec and not have to worry about fasteners coming loose etc...seems worth it to me.

ptheland
05-09-2017, 06:13 AM
An example is the wee bolts that hold the valve body in the nag1.

Yes. That's an area where I would pay attention to the torque specs.

and then being able to torque everything to spec and not have to worry about fasteners coming loose etc...seems worth it to me.

Keep in mind that torque specs have little to do with fasteners coming loose. It has to do with the clamping force created by the fastener. Any screw type fastener can come loose, no matter if under torqued, over torqued, or properly torqued. Keeping fasteners from coming loose requires some mechanical means to prevent loosening - things such as lock washers, jam nuts, safety wiring, and thread lockers (e.g. Loctite).

In the small bits of disassembly I've done on my Sprinter, I've found that Mercedes seems to prefer Loctite (or something similar) to keep fasteners from coming loose.

SneakyAnarchistVanCamper
05-09-2017, 06:33 AM
I doubt thread lubricant is a factor when torqueing the glow plug.... the coefficient of friction drops out of the equation.

Not what my textbook says. Even CAT, Cummins, Detroit, have different torque specs with or without anti seize.

Midwestdrifter
05-09-2017, 10:09 AM
Not what my textbook says. Even CAT, Cummins, Detroit, have different torque specs with or without anti seize.

Friction coefficient, bolt diameter, and pitch are the major factors which influence the tension on a bolt. If you add lube to the threads, you will have much higher clamping (tension) load on the bolt for the same torque value.

The worst case, adding lube can cause the bolt to stretch under a normal torque figure.

The clamping load, and friction under the head are the biggest contributors to keeping a threaded fastener from coming loose. The thread friction also has a smaller effect.

Where is can be used, loctite is my preferred method to retain a fastener. It also prevents corrosion.

ishwashgus
05-17-2017, 08:32 PM
It is pretty simple, actually. You are tightening a bolt by applying torque induced with strokes of a wrench. The bolt will continue to turn until it has tightened, either it bottoms out or hits the end of the threads, or the threads gall, whatever the reason the bolt no longer turns, and since the bolt is not moving the coefficients of friction are of no significance, at that point the worry is not exceeding the torque that causes the material to yield.

Now torque wrenches can spin a bolt faster than it wants to screw in and that can cause a bolt to twist off, that force calculation is impacted by the coefficient friction. Are any of you spinning these glow plugs in that fast? I think not.

Buying a torque wrench is fine, do it if you are unsure or worried, or if you simply wish to have one. I am just saying, it would be a waste for me to buy one. If I am working with steel at these low torque values, I don't need one. Brass, aluminum, softer metals may require me to get one, pretty easy to twist those off..

Seber
05-17-2017, 09:34 PM
Torque reduction numbers due to lubrication can be found here.
http://www.engineeringtoolbox.com/torque-lubrication-effects-d_1693.html