Intermittent "missing" sound

[n8in8or]

Hi guys, a little history:

I bought my Tahoe in November 2013. In December, when the engine was cold, it would make a sound like it was missing on a cylinder and then it would clear up. My first suspicion was glow plugs so I put the Duratherms in. It started much better but didn't take care of the problem. Then I figured it was a sticking injector so I replaced the injectors with marine injectors from a local shop (Diesel Injection Services). They are supposed to be Bosch internals. After changing the injectors it made the noise one time and then didn't, so I figured it was gone. Then 4 months ago it happened again, but this time it made the noise for about 4 days. I took a video and was ready to post on here for help but then it cleared up. Now this morning it is doing it again. It does seem to be an instant thing - it's fine one day and then I start it and it's making the noise. My thought now is a sticking lifter, but with so many other variables in a diesel that I'm not 100% familiar with, I wonder if anyone has any ideas. The sound seems to be coming from the intake and I don't really notice a lot of exhaust noise. I've read about rocker retainers, could it be that? I'm not excited about removing the valve covers just to take a look, but it may come to that. Any thoughts/insight would be much appreciated. Thanks!

http://youtu.be/YcnT2lyIp8U

 

[Will L.]

I would try loosening injector nut, 1 at a time, to see if you can pin point which cylinder it is. I think you're on the right track with lifter or rocker arm button. Do you have a stethoscope? If not do the screwdriver trick.

 

[n8in8or]

Yeah I did a stethoscope during lunch today. The passenger side does have more noises in it compared to the driver side, but I didn't hear a deliberate "clack,clack,clack" I envision the extra rocker lash clearance to sound like but maybe it wouldn't be that pronounced at idle. I am going to start doing fuel line loosening tonight to try to narrow it down, but so far it seems to be the passenger side is my culprit - of course, the EASY side to work on, ha.

If it does indeed to seem to be a lifter, then I'll replace all of them since others are surely not far behind. And while I'm at it I'll do head gaskets and head studs for more reliability with future mods.

I'm curious, how does a failed/bad rocker button affect the way the engine runs exactly? I suspect the rocker falls off the valve stem and is pushing on the retainer instead, but I'm not certain on that. Can someone enlighten me? Thanks

 

[JMJNet]

Wonder if a compression test will verify your issue?

 

[ak diesel driver]

Look in the 6.5 carnage thread to see worst case of what a failed rocker button can do

 

[JayTheCPA]

If it does indeed to seem to be a lifter, then I'll replace all of them since others are surely not far behind. And while I'm at it I'll do head gaskets and head studs for more reliability with future mods.

Seeing as you are looking to tear into the heads, might want to check whether Leroy has any rocker rollers.

 

[n8in8or]

Yeah last time it acted up I ordered a compression tester, but it had corrected itself by the time I got to do it. I think I'll try to do one this weekend.

I was thinking the same thing Jay. I sent an email to him yesterday and I'm waiting a reply. I'm afraid they'll be a little expensive since this is a spur of the moment deal, but who knows, maybe it's a deal I can't pass up.

Here are the latest details:
Yesterday a friend of mine and I took turns listening to the engine with a stethoscope and we are both hearing a clack, clack, clack on the passenger side. It's not as loud and distinct as what I was expecting from when I used to do valve adjustments on Small Block Chevys while they were running, but it is there. I also hear some ticking when I'm driving down the road.

Last night I tried loosening each injector line individually so I could find the offending cylinder. I did all 8 lines and I never did find one that reacted significantly different from the others. This surprised me. Then I realized that maybe I needed to pay more attention and see which one synced up with the noise when it dropped the cylinder but that didn't really work either. It SEEMS that #4 reacted a little less than the others when I cracked the line, but it may have just been a perception thing, not sure.

Once I thought about it some more though, I think this makes sense - if it's an exhaust lifter that's giving me the trouble, this means that the cylinder pressure isn't able to fully escape the cylinder, so when the intake valve opens it releases into the intake track and that is the noise. So the cylinder is still functioning, just not at 100%. When the fuel is turned off to the cylinder that completely kills the cylinder and it would be a significant change still. This is where a compression test would tell me something I think. If my theory is correct, then I'm lucky it was an exhaust lifter and not an intake lifter because I may not have really noticed a problem since it still runs smooth and makes good power. Who knows, maybe I have some other sad lifters that I don't know about?

Today I'm going to start ordering all my parts so I can work on this next week. I've been wanting to do the head studs anyway so that's a good thing, I just wasn't planning on doing it right now, but oh well, I guess the truck forced my hand.

I'll report back as I find more out. Now off to the carnage thread.....

 

[Will L.]

The problem is being intermittent, you have to check when it's doing it. If you have a temp gun, keep it in the truck so you can hop out and shoot the cylinders. If it is an lifter or rocker arm, it will show up on the temp gun. The hard part of trying to figure it out with a compression tester is- if it is acting up when you shut the engine off, you pull all the glow plugs and start checking the problem can go away.

It goes against my rule of don't throw parts at a problem but it should cure the problem and improve efficiency of the engine with the rollers along with never again being concerned about rocker buttons. I can't imagine anything else being a cause. If you can afford to, doing new lifters & roller rockers, and head studs (best price is Leroy on those anyways while your ordering). Get Fel Pro or Victor Rienz head gaskets. Some people go with the +.10 gaskets as an attempt to ensure better sealing at a loss of a little compression. I've done somewhere in the neighborhood of thirty 6.5 rebuilds and never had a problem with standard thickness. Around half were torn apart for having blown factory head gaskets due to overheating.

2 Things to remember, when was the last time your torque wrench was calibrated, and do you have knuckle band aids on hand?

 

[n8in8or]

Great advice Will, especially on the knuckle band-aids! Funny you should mention all that....I just ordered my roller rockers and head studs from Leroy! (thanks Leroy!) Is it wrong that I'm kind of glad the problem showed up? ha. Good thought on the temp gun. So far it's still consistently making the noise since yesterday morning. I'll throw the temp gun on it today and see what that tells me. I agree with you regarding throwing parts at a problem, but the head studs were on my to-do list anyway, and the rockers will be a nice improvement and piece of mind. I used a little credit, but I don't really want to have to pull the valve covers off again so might as well do it all at once.

 

[Will L.]

Well then you can count this as an upgrade for longevity, and if it 'just so happens' to solve a problem, so be it!:302:

 

[Burning oil]

Hi, Nate. I thought this story was sounding famliar. Anyway got your order mailed right a closing of post office today so it may not show up on tracking til tomorrow (well later today after 12pm now).
Of all the sets I sold only one has installed and posted pictures. If you get a chance a good write up would be great.
Thanks again.

 

[n8in8or]

I will definitely post pics, of both the head studs and the rockers. I can't wait to get it all installed next week.

 

[n8in8or]

I got the heads off today. I found a couple things that, are interesting. When I took the intake off, I noted a lot of oil in the #6 intake port so I knew that was likely my problem cylinder. When I finally got the valve cover off, I didn't find an exhaust rocker with a lot of lash though, so this surprised and disappointed me. I used the starter to turn the engine over with the valve cover off and didn't see anything unusual. So I continued with the tear down. Where it got really interesting was when I got the heads off - both heads had 1 cylinder each with an unusual burn pattern in the combustion chamber. Even more unusual is that is was the same cylinder in the head when viewing them side-by-side. The pattern kind of supports my collapsed lifter theory in that the residual combustion gases aren't getting fully exhausted so they're coming back out of the intake, but I'm not 100% sold on that now since I didn't feel a loose rocker. It could be that once it's running the force on the valve from the combustion is collapsing the lifter, but again it's just a hypothesis at this point.

What I am concerned about now are 2 things: 1) that my valves and seats are ruined from whatever is going on here and 2) maybe I have a couple injectors with a bad spray pattern or are popping at the wrong pressure. My plan of attack tomorrow is to take the injectors to Diesel Injection Service and have them test them out and fix if necessary and take the heads to the machine shop for a valve job. Any thoughts from you folks that are smarter about diesels than me?

I gave the heads a quick visual check and I think I see a crack between the valves in one chamber, which I've read about in here before. That's nothing to really worry about on these correct? Also, I'm wondering if it's worth sinking the money into these heads to have them rebuilt.....what does a pair of heads for the Optimizer( or whatever good heads are called) cost? And where do you find them? I emailed Leroy to see if he can get them since he gets complete Optimizers and P400s, but if there's anyone else please let me know, thanks.

Oil in cylinder 6 intake


Close up of 2 cylinders in driver side head


Driver side head


Close up of 2 cylinders on pass side head


Pass side head

 

[Burning oil]

$800ea brand new AMG P400 head with hardened valve seats.
$525ea brand new AMG/Optimizer type head with better metalurgy.

In the pictures you posted it looks like you have the smallest precups. Some larger ones can help performance.

 

[n8in8or]

I hadn't even looked at the precups to see what ones they were. They've been soaking in the parts washer overnight so I'll take them out, clean them up and take a look. I do believe they were reman heads because they have stickers on them which I think are those heat sensing stickers on remans. I was thinking today that I would just lap the valves and see what I have instead of taking them to the machine shop, but if I do indeed have the small precups then shoot......who knows...... That would probably explain why it made more smoke than I liked too.

And......it's Christmas in September and Leroy is Santa! Thanks Leroy!!

 

[n8in8or]

Ok, just came in from the barn and I have MUCH more clarity now. First, lookie what I found when I looked at the lifters in the engine:



Note the cup in the lifter out of place, that's the exhaust lifter for the #4 cylinder. So the exhaust lifter theory was correct after all. That doesn't explain my #6 intake being extra oily, but that's the lesser issue. Also, as far as the weird looking combustion chambers, I realized that both of those cylinders are the ones that have the EGR crossover port attached to them, so there must have been something going on there. I have a non EGR lower theintake now so that isn't an issue now.

I am still a little concerned that the valves aren't sealing great, so I'm going to lap the valves just for a little extra assurance there. I would love to buy some good heads right now, but I just don't think I can afford it unfortunately. I'm going to put them or a whole Optimizer long block on my wish list for sure though.

And finally, I did confirm that they're square precups in the heads, so I ordered a set of diamond precups to put in the heads while they're off. So I won't be getting it together this weekend, but that gives me time to do some house projects I'm needing to do and do a good job cleaning my parts up really well and inspecting everything to make sure it goes together well.

Side note: I had an interesting experience yesterday with the new lifters I bought. I bought Melling lifters of Autozone.com because with their current discount they were only $8 each. When they showed up yesterday I found them to be mismatched. The bodies were different looking, 1 was rusty and some had needle bearings while others had bronze bushings!! The bronze bushings did not feel good...they were noticeably not as slick as the needle bearings. So I went to the local Autozone and they found that the warehouse had only 7 in stock (which was the exact number of bad lifters I had), so they ordered them and low and behold they all had the needle bearings. So I ended up with 16 lifters with needle bearing rollers. I guess I just wanted to mention it so people could keep that story in mind when getting replacement parts from vendors. I don't blame Melling or Autozone for that matter....I think someone did a switch-a-roo with their parts in the box and then returned them.

Nothing's easy, but I'm excited about how it's going to run in the end when it's back together once I have diamond precups and roller rockers! Once I get a better turbo in the winter/spring I should really be rockin'.

 

[Burning oil]

Lifter is no bueno.

Looking forward to more progress.

 

[Will L.]

Cool on finding the lifter issue, and getting all the good new lifters.

Now then, about your head- you said there is a crack in between two of the valves!?! Please clean it up and take a close up of that for us to see. I never heard of a crack in between valves being ok. I have had to run heads like that before, but I also have had turn a v8 into a v7 and 1 dead hole just to drive for a while. Much like the lifter- no Bueno.

I would make sure about the crack before spending $ and time on valve lap and different pre cups. If the heads are ok then yes valve lap and bigger pre cups will help. About the oil in the intake, how oily is the intake manifold- can it be coming from the cdr?

 

[n8in8or]

Oh boy, that isn't what I want to hear, Will....and I was starting to feel so good about where I was with this! I'll take some pics in the morning and post them. Thanks for weighing in. Unfortunately I just don't think I can afford the Optimizer heads right now, so I'm not sure what my options are at this point. I guess I'll post pics and take it from there.....thanks.

 

[Chevypoor]

Cool on finding the lifter issue, and getting all the good new lifters.

Now then, about your head- you said there is a crack in between two of the valves!?! Please clean it up and take a close up of that for us to see. I never heard of a crack in between valves being ok. I have had to run heads like that before, but I also have had turn a v8 into a v7 and 1 dead hole just to drive for a while. Much like the lifter- no Bueno.

I would make sure about the crack before spending $ and time on valve lap and different pre cups. If the heads are ok then yes valve lap and bigger pre cups will help. About the oil in the intake, how oily is the intake manifold- can it be coming from the cdr?

I had a set of lifters do that to me- mine were so bad they actually cut a groove in the pushrod!

On the cylinder head- this will draw some flak I am sure but here is my limited experience/ opinion. I have seen too kinds of cracks in the valve bridge. The first is a faint hairline crack that is almost invisible, this a crack that is a ticking time bomb. I had a set on that were cracked on the first 6.5 I worked on, a 1995 c1500 vin F truck. The #8 was not leaking and the #2 was just in the early stages of ingesting coolant. I cleaned the heads up and re ran them. Had that truck for 30k+ more miles and it never ran hot, nor did it throw any codes. Power was good- ran like stink. It was only used for limited towing and when I did tow it was usually 5k or less. It did however eat a bit of coolant- a quart or so every 3000-5000K. Never smoked.

Big T had a full blown crack in the #2 head that was so bad it would eventually push the coolant out of the overflow. It did not do that until the po had the heater core spring a leak while towing and she got hot. My suspicion is that it had a hairline crack that "blew" when the temperature spiked.

To answer the question if you have not had any problems with the heads pushing coolant or blowing bubbles in the overflow then you could run them, knowing they are a potential problem. You may get alot of miles before they become an issue.

With the heads off I would check with the local machine shops- the heads can be fixed. Remove the freeze plug on the intake side of the head and run a reamer through the coolant passage between the valves. Then they can press in a bronze valve guide liner. That should cost alot less than a new head.