I have been reading here about alternate methods to torquing the hold down bolts for the injectors. This winter I replaced my old stock split shots with new alliant single shots. I installed the injectors into a cold engine and torqued the hold down bolts to 10 ft lbs. I did not ever go back and re-tighten.

Is it suggested to go in and re-tighten the injector hold down bolts to 10 ft-lbs after the engine has been heated up and cooled down? What are some symptoms of a loose injector? I am imagining premature wear on the injector cups, low compression and maybe some mixing of oil into the combustion chamber.

Did any one else just throw the injectors in like me and go back later to retorque only to find they were all fine or were some loose?

Thanks,

David

 

I believe that some here re torque the hold down bolts while hot after running to operating temperature on initial installation.

 

Can't hurt a thing by checking torque, anything that heat cycles especially may tend to loosen somewhat and takes a few cycles to stabilize. To be clear that means checking the torque in the tightening direction at the torque spec.

 

Most recommended method here is 120 INCH pounds with an inch pound torque wrench. Then warm up engine and re-torque to same value. Seems like most people report the re-torque was needed as some injector became loose. Other folks don't bother with the hot torque and have no problems. So YMMV.

A foot pound wrench set to 10 is not going to be accurate. But hey if you have no operating issues now that's good. If it were me I'd go back in with the proper inch pound wrench and give it a snug for peace of mind.

 

I completely agree on every point, especially about using an "INCH Pound" rated torque wrench.

If you do decide to go back in and verify proper torque, it could save you from having to replace injector o-rings prematurely and if the injector hold down bolts are far enough below spec: injector cups. Cups are NOT a fun chore.

 

Yeah the spec is 120 in-lb. If 10 ft-lb was OK, that's what the spec would be. It's in in-lbs for a reason. If you aren't having any issues that great but I would go back and hot-torque them to 120 in-lbs if it were my truck.

 

Would a bad torque show an injector cup failer, soon or down the road? Was just in on mine with ft lb torque and man, did #2 make a god awful sound being fired up. Turned off then on again with no noise. Have put 1800 miles on since with no cocktails being made...

 

Just to clarify and sorry for "changing" the story, but I did use a 3/8 drive inch pound torque wrench adjustable from 50-250 in-lbs. It is one of my favorite tools in my box to use.

3/8" Drive Round-Head Micro-Adjustable Torque Wrench 50-250 in-lbs.

If I get a chance, I will try to sneak in there and retorque to bolts. Thanks for the help.

 

I'm not questioning folks going in and re-checking the holddown torque. My only observation is that you can only check half of them. The other half go in before the injectors. Whether there's a difference for those, as they tighten against a fixed support - although both the head and the bolt can change dimensions due to thermal expansion - versus the ones you can check which tighten against the injector clamp, I don't know. All are subject to vibration, oil and everything else in there.

The last time I had my injectors out, I replaced all of the bolts, and thoroughly cleaned and dried both the bolts and holes with acetone, and used Loctite. Didn't re-torque, no issues here.

 

There has been plenty of discussion on this issue. I am not an engineer and I did not study this specific issue extensively but I am getting old and have worked on stuff all my life. I do not believe that the issue is 'hot torque' or bolt coming loose, I believe it's a matter of the injector settling into its seat a little after having been run. People are reluctant to give the torque value that they use but they have reported good luck using a little more than that factory spec the first time around and not having any problems.

 

If the injector isn't tight in the bore, it can move around a little bit. The injector rattling against the soft brass cup doesn't do it any favors. If it's loose enough, yes it can cause a problem down the road.

The hold down bracket is a basically a lever. It's fixed at one end (the top bolt) and as the bottom bolt is tightened down, it pushes the injector down. You don't need a torque wrench for the top bolt. Just tighten it down good. The torque on the lower bolt is what's important.

It could easily be engineered to work the other way around - crank the bottom bolt down nice and tight and use the top bolts to control the hold-down torque, but you don't need to set the torque on both ends.

In my very limited experience, re-torquing isn't necessary, but hot-torquing them helps tremendously.

 

Think pry bar. The top bolt has a collar, and it is seated. The bottom bolt never seats - it is to apply a very specific pressure to one side of the injector hold-down pry bar. The top bolt just keeps the other end of the pry bar held down, and you can't turn it with the injector in place.

Many people who have gone in to check torque find the need for a love twist - even with the factory torque. The first thing most people mention after tightening things down, is how the engine runs quieter than before.

 

While you're correct about the lever arm, your argument about the requirement for a torque spec on the top bolt is wrong. Really, truly, class is over wrong.

Yes, the top bolt is tightened directly against the head, and the bottom bolt compresses the lever. But the bolts themselves don't see anything different. If you're thinking that the bottom bolt isn't tightened "against" anything, because there is space between the lever and the head, you're wrong. It's tightened against the lever, which is tightened against the injector, which compresses and finally tightens the copper crush washer against the head. It's a mechanical linkage which has zero slack in it, similar to a flat tappet valvetrain.

For certain that top bolt could be loose and you would still be able to fully seat the injector and torque the lower bolt, it's just that the lever would be at a slightly different angle and the bottom bolt a bit deeper in the hole. In this case however, all the vibration from the engine could act on that loose top bolt, and if it backs out even a touch, than the torque on the bottom bolt would disappear entirely, as you've now introduced some slack in that linkage mentioned above. That top bolt absolutely needs to be properly tightened, and "properly tightened" is solely achieved using a torque spec.

The torque on the bottom bolt is entirely dependent upon the other bolt staying tight, while it's torque is independent. I would check it every time the injector comes out.

Edit: Rich - you said the "bottom bolt never seats". Replace the word "tightened" in my run-on sentence above with "seated". That bottom bolt is seated, just not as directly as you think.

 

Exactly!

The top bolt is what was causing the injectors in the e99 to loosen up all along, the last 4 years, which is the sole reason that I installed new bolts, cleaned the holes/threads in the head, and added loc-tite to them: the top bolts, when I installed the 175/80's last winter. I then "hot-torqued" the lower hold down bolts after running the engine to about 180* EOT with the VC's held in place by 4 bolts.

30K later the engine is as quiet as it was 7 months ago using the same Android app to monitor decibels. The torque value used was north of factory by 15+ inch/pounds as it has been for about the last 3 yrs.

 

As long as it doesn't come loose, it's fine. I used an oil-tolerant variety of loc-tite on mine and I'm not worried about them at all. I didn't use a torque wrench but they are not coming loose.

This is all perfectly obvious to anyone (even me!) with a reasonable amount of mechanical aptitude who has replaced injectors in a 7.3.