Can intake cam be locked even if threads are damaged?

Big Montana · **Posted:** Wed Aug 22, 2012 10:44 am

I had my timing belt replaced by a dealer and they stripped the threads on the intake camshaft locking pin hole.

My hole:

Replaced bolt with aluminum threads that I found once I pulled this bolt out:

What it should look like:

Cam locking tool only has a few threads:

I'm going back tomorrow to have the control arm recall performed, and I will be showing them these pictures. I will tell them that I'm concerned that in five to seven years time when I need to replace the belt again, the mechanic will be unable to lock in the tool to hold the cam.

Here's my question: Is the dealer going to agree with me and fix the problem or are they going to claim there's another way around that step in the timing belt change? Is there a different tool or method that they will tell me about that will be just as effective? Perhaps he can lock the pin in front of me showing me that there is enough thread to hold the cam in place. If this is no big deal then great. It seems like the alternative will be to replace the entire head cover and that would mean taking apart the top of a perfectly functioning engine. Needless to say I don't trust them to do that type of work. There are a lot of little parts, and they couldn't even get one of my heat shields back on.

The Jeep is great right now, and I don't want to cause problems with it, but I don't want to be stuck in five years with a massive fix that I didn't cause. I just want to know what my options are. This is a certified dealership, and they may take care of it perfectly once I speak to them tomorrow.

Thanks

FYI I like the full torque Eco tune and the ECU tune from GDE that I got yesterday. I have a stock TC and there was no shudder with a tone of heavy acceleration on my way home from their shop.

geordi · **Posted:** Wed Aug 22, 2012 1:16 pm

The answer to your thread question is "yes... With caution"
It is NOT correct according to the service manual which stipulates a torque value for those threads. I disagree with that as well, as ANY torque or tool use on those keys can do what happened to yours, OR chip / hurt the cam. Those should be put in finger tight ONLY, that is all they truly need.

Without the threads there to hold the key, there isn't any way to know if the cam has wobbled up to half a tooth in either direction while the cam pulley is off - the machined tolerances SHOULD be tight enough that it wouldn't... But you can't know for certain.

This is a tough situation, good luck with them. In my experience, a "certified" dealer doesn't mean much more than one that isn't certified... They all suck.

warp2diesel · **Posted:** Wed Aug 22, 2012 9:22 pm

Since the plug seals on the seat and the alignment plug seats on the seat instead of the threads, the threads can be repaired with a thread repair device such as a helicoil. Just make sure you pack your drill and tap flutes with grease and be very careful when you do the operation and not damage the hole the pin part fits into. Then line up the cam like you are ready to put in the locking pin and blow out the hole with compressed air so the alignment pin will properly seat.
Not rocket science, just common sense.
Since the thread repair operation is not in the Chrysler Flat rate guide, no Chrysler Tech will want to do it because they can't beat the time and make more money. Anymore, Techs are like Pedophiles in a school yard who all fight for the easiest mark/job that makes the most money. I do not know first hand, but I have heard that Hookers in a brothel have more respect for one another and tend to be more polite to each other when serving customers. :ROTFL:

Good Independents will do the job on Time and Materials, do it right and it will work when they are done.

geordi · **Posted:** Wed Aug 22, 2012 9:41 pm

Sorry Warp, you are wrong in this case. Yes, the housing COULD be drilled out because the key seats against the flat portion of the outside of the head - But you are NOT DRILLING into the cam. There is EMPTY SPACE behind the 3/8" or so of threaded aluminum. That is why I believe that drilling it will not work properly, because if your hole or the collared insert aren't lined up perfectly horizontal, then the key will not slide into the cam properly - it will bind or be stuck.

This is a precision setup and one of the more important engineering disasters on this vehicle. There is no good reason I can fathom why the cams were not keyed properly to their pulleys, the number of teeth on a belt is known, the spacing is known, and the cams and crank could easily be engineered to perfectly match a new belt when all are in position and locked... IF your engineering department didn't get their degrees by mail.

Big Montana · **Posted:** Thu Aug 23, 2012 12:35 am

I know that they can retap holes, but my very concern was whether they would do it and whether or not the same locking tool could be used to hold the cam. I pictured the hole being off. I know that I don't want my engine torn apart for a stupid bolt hole that won't matter for five years, but I want to be sure whatever line they feed me is correct.

I was even wondering if there is a way to hold the alignment without the pin. If they can convince me of that then I'll go with that.

geordi · **Posted:** Thu Aug 23, 2012 10:36 am

You can't hold the cam in place without the pin. When you take the cam pulley off or even loose, the cam itself is "balanced" on the center of at least a couple lobes and if it moves even slightly, it WILL SLIP to a place where all the valves are closed - about 4 teeth advanced of where it should be.

Without the cam key, there is no way to grab that and hold it properly in place. Even with wrecked threads, that would offer more help, possibly keeping it within a half-tooth of correct... Certainly better than nothing at all.

When re-assembling my valve cover for a test just recently, both cams shifted the same 4 teeth or so advanced from the 90-ATDC position, because I did not have the keys in. I was OK with that, I wanted the valve cover to seat properly and not dislodge any rockers, so the LEAST amount of pressure on the valves was desirable.

Turning the cams back to the proper position so the keys could get seated, is when I discovered that the keys seat on a "peak" of one or more of the lobes, and I had to use a BIG channel wrench to turn the cams from the front ends - It was quite difficult to get this back in line so the key would fit properly. The tolerance is very small, as it needs to be.

Big Montana · **Posted:** Thu Aug 23, 2012 11:02 am

I was told today by the mechanic that the techs can use a second exhaust locking pin in the hole because it has more threads or a modified tool that has more threads to grab farther into the hole. He also told me that a bolt can be cut down to the correct length to also act as a locking pin. I guess I'm just going to go with that at this point. If the Jeep is still running in five years I'll find out if this is the correct call. I really don't want to force them to pull the cover. I just wanted it documented.

I got a chance to ask him how my belt broke while taking it off, and he said it happened while trying to lock the fly wheel. He had the two cam pins in and it broke while he was rocking the gears trying to line it up. He walked away before I realized I should have asked how he got the fuel injection pump back in line. Keith told me there is really no way to know if it is aligned while it's running. That being said. I guess if I can't tell, and the Jeep sounds good then there is no reason to worry. I read the other comments, and also learned from Keith, that the pistons in the pump are meant to send fuel at specific points to keep the pressure up in the rail, and if the timing is off it could have less pressure for certain injection events.

Either way, I think I'm happy. Thanks for all the help on this board. This really is a great asset to understand what's going on with this little Jeep.

Dennis MacGyver · **Posted:** Mon Aug 27, 2012 5:25 pm

I've been doing rubber belt changes (at home) on diesels for about 30 years now. From my 1st VW Rabbit to an '85 BMW 524td to Land Rover 300tdi's.

The thing I learned from the beginning (before removing the old belt) was to make paint marks on the belt and corresponding cogs on the main crank, the IP and cam(s), yes I used locking pins too. Then transfer those marks onto the new belt AND just to be extra sure count the number of teeth on the belt between the paint marks. Then install the new belt using those new marks to insure I got the belt back on properly. I also always changed the belts sooner than the recommended mileage time frame.

warp2diesel · **Posted:** Mon Aug 27, 2012 9:19 pm

geordi wrote:

Sorry Warp, you are wrong in this case. Yes, the housing COULD be drilled out because the key seats against the flat portion of the outside of the head - But you are NOT DRILLING into the cam. There is EMPTY SPACE behind the 3/8" or so of threaded aluminum. That is why I believe that drilling it will not work properly, because if your hole or the collared insert aren't lined up perfectly horizontal, then the key will not slide into the cam properly - it will bind or be stuck.

This is a precision setup and one of the more important engineering disasters on this vehicle. There is no good reason I can fathom why the cams were not keyed properly to their pulleys, the number of teeth on a belt is known, the spacing is known, and the cams and crank could easily be engineered to perfectly match a new belt when all are in position and locked... IF your engineering department didn't get their degrees by mail.

I said nothing about drilling the cam, who in #ell would drill an alignment hole in a cam? I described a way to just fixing the threads. Before and after my 14 1/2 years of running a shop, I fixed many more engines that others walked away from than you will ever dream of. Your record of CRD disasters speaks for its' self.

Can intake cam be locked even if threads are damaged?

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