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Low Compression

20K views 18 replies 3 participants last post by  Crackerjackshot 
#1 ·
Hello all, I've been a member on here for over a year now and I want to say first that I have learned a ton one here and would like some opinions on this issue. Here we go...

So, took my 6.4 into the shop yesterday thinking that I was going to get injectors 6 and 8 replaced along with an oil cooler. A year ago the injectors showed borderline as number 6 was pulling back fuel and number 8 was pushing extra fuel. Also my deltas have consistently been about 20 degrees on the nose (215ish EOT, 192-194 ECT) for basically the the whole year since I deleted it and could monitor it. During the summer with the AC on it will hit up to 222 or so when it's hot out.

I have told them this and they still believe that the deltas are not enough to warrant changing the oil cooler. He thinks it's not going to make much of a difference. Opinions on this please??

Also, this morning they ran a computer compression test and apparently when cold the number 2 and 8 cylinders are 4% low on compression. So now they are saying that that is the reason the injectors are pushing extra fuel, not an injector issue. The prognosis on something like this didn't sound very good. Pretty much complete engine overhaul or new block. They have said that they are going to get the truck warm and run the compression again and see what it does. They are saying that they have seen trucks run like this for years but there are no gaurantees that it won't get worse so....

Just how bad is this? What do I do if the compression is not better warm? What do I do if it is better warm? They called and made sure to let me know partially because the truck was also getting a lift and tires and I've already started down the road of putting a fair amount of money into modding it and they wanted me to be able to have this information before they go ahead with the lift install and stuff. (which in all honesty I don't know what to do if it doesn't get lifted, tires are completely shot on the truck as is and 37's wont fit on stock).

They were asking if I wanted to do a full compression test and I'm kinda hesitant because I feel like I'm going to pay for 4 hours of work to then find out probably the same news. And in all reality I have only owned this truck a year and thought I had several years to get the money together for a new engine and transmission for HOPEFULLY around 200k or further miles. I just haven't had the time. I cannot afford this and in all honesty, I wanted 2 engines to take me deep into my life, I don't really feel like dropping that much money on a motor right now because it will only take me as far as what I hoped this one would meaning I'd pay for 2 full engines in this truck vs one.

I'm just a bit flustered right now, I'd really love any input right now. Thanks.
 
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#2 ·
First. Yes you need an oil cooler, it will absolutely make a difference. Second, get an actual compression test done on it. 4% on a relative compression test doesnt mean you need a new motor. How many miles on the motor? When wad it deleted?

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#3 ·
Hmm. Weird. I didn't see my signature show up but figured y'all could see it. Either way is a job 1 2008 with 95000 miles on it. Deleted at 84k. I've owned it since 82k.
I think it's a little bizarre what they keep saying about the oil cooler as well. They drove it up to temp today and once again said yeah you don't need to replace it. This shop is very highly rated powerstroke only shop. But yeah, that kind of answer has me scratching my head.
Their gonna call me after doing the test warm and give me the results and their opinions. I think it's bizarre also that when we did the test that first showed the injectors, the same test showed that power and compression were all normal. Now they're saying that the compression is the REASON that the injectors are doing what their doing.
Any chance at a head gasket? I HAVE noticed that if I fill the coolant to between the lines it always sstyles back down to a .5 inch - inch below the lower line in the Degas. No puking though. (But also never runs hard, never seen anything higher than about 30psi boost or maybe 2600 Rpms)
What I would REALLY like is maybe to list out possibles. Can't be more than about 2 or 3 possibilities right?
Oh and I'll get more info on this but even with 2 and 8 having the compression issue, 6 still seems to be holding back on the fuel. So it might still need to be changed. Thinking if the cab still comes up I'll just bite the bullet, try the oil cooler anyways and have the head gasket looked at? If bad I'll stud.
Thank you so much for the reply and any help. I hate getting on this site but love that is here.
 
#4 ·
Make them do a manual compression test... If they are going in to do an oil cooler and injectors it really isn't that much more work to do a compression test before hand.
A relative compression test can point you in a direction, but you can't diagnose low compression based on a relative compression test alone............ Any powerstroke shop should know this especially if they have any experience with 6.4s.
 
#5 ·
Ok. That's what I'll tell them when they get ahold of me. They had offered to do the test warm which is what they're doing. Will the results tell me anything based off of they get better or not when warm?
Something I forgot to include was also that the numbers improved slightly when they put the engine under a slight load. Not sure if that indicates anything. Though I guess that makes head gaskets almost an impossible possibility right?
At the moment they aren't pulling the cab for the oil cooler because they are saying it doesn't need changing and injectors don't either. Was just trying to see if I could save myself 400 bucks to diagnose something that means I have to sell the truck anyways.
The guy that runs the shop was saying this happens when pitting occurs in the cylinder? That's why he was saying reman block or overhaul on the one that's in there.
 
#6 ·
Oh. And just top include, they knew to do the manual test, just offered to do this first.
 
#7 ·
Ok well slight update. I was kinda irritated, I thought that they were going to do the warm test right then and get back to me soon but I didn't get the call until after 5pm which means no manual compression test until tomorrow morning. They said that during the warm relative test the numbers were the same which leaves me scratching my head since the injector issues were there last year but not the relatives compression problem BUT YET the injectors are BECAUSE of the compression?!

He said they'll do a headgasket test and do the manual compression on 2 and 8 tomorrow morning. I've been all over the forums and stuff all day and reading through the low compression problems I don't think I read even one where it was just unexplained scoring in the cylinder. I would think cracked/melted piston, which then I would think that compression would be worse than it is, plus I should have unusual blow by which I don't. It's pretty much normal as it has been explained to me for a 6.4 (doesn't blow oil fill cap off).

So at this point I just don't see where their thought process is, that I have just weird unexplained scoring in the cylinder walls. He's still talking about if I'm going to want to keep the lift and tires off the truck and sell the truck or try to put a new engine in... I asked if there were other options and he doesn't seem to be providing anything like honing out the cylinder at all like I've seen in other posts.

In all reality I'm just in no position to make any of these decisions. This could not have come at a worse time. I am beyond stressed with about 5 other major issues in my life. No option is good. The thought of having to list the truck and everything is just about the most horrid thought I can think of, with the only thing worse being trying to replace the engine.

I feel like I'm going to be leaning on opinions off of this thread a lot because it seems like their "options" don't really leave me with many. Let's just say that the manual compression comes back with similar results, and the head gasket test comes back without issue. What would ya'll do on your truck? Go ahead and have the heads pulled? From my research it seemed that bad valve seating could just as easily be the culprit (and honestly sounded more likely for something low like a 4% loss). But he has me scared into the idea that if I pay to pull the heads and inspect everything I'm just going to be paying to then find out that it requires a whole new engine.
 
#8 ·
My opinion. You may have a couple injectors a little off but your motor is fine. I would do the suspect injectors and oil cooler and keep driving it.

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#9 ·
Possible that the injectors are causing the compression vs the other way around??? I've been reading around and the consensus seemed to be that injectors can't (ok, can't is a strong word, not likely to) cause compression issues? It WOULD fit with the idea is that I had no relative compression issue last year while I did have the injector issue.

I guess I just have to wait until tomorrow... hope I can sleep tonight. How is the leak down test conducted? Can that definitively point to a valve issue instead or if it leaks out pressure could it still be going out the bottom to the crank case?

For the first time ever this site is actually helping my blood pressure lower vs talking to the mechanic who is borderline convincing me to sell the truck or get a new block.... by the way. What does it cost to get the motor rebuilt?
 
#11 ·
Relative compression is exactly what it says. Relative compression. I believe injectors can throw it off if there is an issue with them, but you won't know if there is an issue til they check actual compression. I'm playing Internet mechanic here but I bet your motor will check out fine with a compression check.

I'm wondering why a shop would steer you away from an obvious issue like and oil cooler but insist that you need a new motor little to no reason and without actually checking compression.

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#10 ·
Oh yeah, one more thing. The guy said he would only do the compression on 2 and 8 which could save time on it and help save me money. Is anything being jeopardized by doing the test this way? Should I call him tomorrow and tell him to just do the full test?
 
#12 ·
And when it checks out fine, nut kick this guy and tell him to go fly a kite

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#13 ·
Lol. I'd be so relieved I probably wouldn't be able to do anything negative haha. My stomach has been in my throat all day.

As for the oil cooler thing, I guess what they keep saying is just how my deltas really aren't that bad and the temps I see aren't in a danger zone yet. It's possible that the fact that I towed 6k pounds 14 hours, and it didn't change the temps one bit, could also be prompting them for that? I guess they just see it as not worth the amount of money that it is to do. I just hate knowing that my truck is doing something that it isn't supposed to do. And I can't imagine that running oil (even just slightly) over regular temp can be a good thing. I have full synthetic now so I guess that's a good thing but still...

And I wouldn't really say he's INSISTING on a new motor. But he certainly sounds really grave about the whole thing. Like I said, part of what was supposed to happen was lift and tires while it's in there and he keeps mentioning things like not putting it on and keeping the lift for a different truck and what not. That kind of talk is scary to me. He also gave me the website for a place in NC that sells 6.4 short/long blocks and complete engines. And hasn't mentioned once about possibly honing out the cylinder, or anything like that that I would believe would be maybe step 1 to look at with new engine being step 3 or 4.

I'd really honestly be at least a slight bit perplexed if the motor came back with an issue like that. But I'm not the type to think everything is going to be ok to then get blindsided. I usually think the worse and then hopefully have a really good day when it doesn't turn out to be so.....
 
#14 ·
Hey guys, just wanted to ask real quick how long some of these tests usually take a shop to conduct. Right now it seems like this shop is literally planning out one thing a day to do on the truck and nothing more. He told me yesterday that the compression test would be done today. I just called at 215 PM and it hasn't even been done yet which means I'll barely get an answer by 5pm. I'm getting fed up with this whole process taking the better part of a week and I don't even know whats wrong.

This paired with the fact that they say things like (don't change the oil cooler) makes me start considering pulling the truck from them and going somewhere else. What do ya'll think? Am I being unreasonable? I feel like if a test takes 4 hours to conduct and their shop opens at 9am. Then I should be getting an answer by 2pm, not saying they haven't even started it yet.
 
#15 · (Edited)
Some side notes...
When the question of compression comes up any reputable powerstroke shop will tell you the bad news about 6.4s killing themselves... However, any tech that even points that direction without a complete manual compression test (they should test EVERY cylinder, as Lipka said... Bad injectors can skew a relative compression test and they may miss something if they only test those 2) needs to go away. Again, 6.4s are known to have compression issues, cracked pistons, etc... That doesn't excuse their lack of proper diag. Second, everything sucks on a 6.4 unless the cab is up... They probably don't want to work on your truck and aren't in much of a hurry. The money is in 6.0 repair, 6.4s tend to sit on a lift and cost shops and in turn, you money.
The oil cooler... Yes, a slightly clogged oil cooler won't cause an egr cooler failure like it does on a 6.0. But, it IS causing your oil to run hot... A 15* delta is the point at which Ford calls for replacement. I wouldn't say go in and replace the oil cooler instantly however. Do a FULL chemical flush and refill with red elc, then get that oil cooler replaced. Again, any reputable powerstroke shop would tell you to do just that... Flush the crap out of her, fill with elc, then replace the oil cooler when you have them go in for injectors. This is all provided the motor checks out during a compression test, and if she has a smooth crank then I bet you are fine. Yes its gonna cost a tad bit more to do the compression check... But its a lot better than doing everything else only to find out you have a few washed out cylinders because of over fueling injectors...


A powerstroke shop recommending a half a** diag/repair for a 6.4 is a red flag to me... It says they don't want to work on/aren't comfortable working on these trucks.
 
#16 ·
Ok guys. I've got some numbers for you. I would really like some input on these. The shop is waiting for my answer whether or not to go ahead with the lifting and tires and checking on some of the minor issues I have (chugging brakes and rust in transmission tube).

Manual Pressure test results (2 tests performed) (only performed on drivers side because that was the only place with either injector fuel trim off or relative compression differences)-

Test 1-
Cyl 2- 310
Cyl 4- 320
Cyl 6- 330
Cyl 8- 310

Test 2-
Cyl 2- 313
Cyl 4- 340
Cyl 6- 325
Cyl 8- 303

Fuel Trim Results for all Cylinders:
Cyl 1- 0
Cyl 2- +9
Cyl 3- -5
Cyl 4- +1
Cyl 5- 0
Cyl 6- -11
Cyl 7- -5
Cyl 8- +9

IF my memory serves me correctly this fuel trim is almost identical to what it was 1 year ago. Except for cylinder 2. I don't remember it pushing that much fuel. But 6 and 8 were the trouble cylinders at almost those exact same numbers.

And his EOT delta results were obviously done at idle or something similar--- EOT 190, ECT 188 but I know that the truck doesn't actually run that cool on the EOT.

The thing that I'm kinda irritated about is that apparently they aren't "set up" for a leak down test. So I don't get to know which way the air is going. He tried to say that they wouldn't be able to tell which way the air is going anyways. And to me, I'm kinda thinking that is the whole point of the test?

Passed HG test.

They are saying right now that they would do nothing, and just drive it and I should get a few years with it at these numbers. They are saying no to injectors, and the oil cooler. And apparently they are cool just letting the cylinder pressures be what they are. I kinda wish I could know if it was valves or piston rings or something. I kinda feel like I took my truck into a shop to get it fixed, and it's not getting fixed.

What are some opinions now? Please do reply, I am looking for all angles to look at this from. I quite frankly just don't really trust their opinion anymore. The first and most prominent question here would be, would you be comfortable enough with the truck to go ahead and have the lift and tires put on? (The tires on the truck are completely shot and those are the only tires I have to put on it.)

Secondly- Should I call them and force them into the oil cooler? Should I force them into some injectors?

Here's an idea that I have, I have thought about having them just put the lift on, and check the other minor issues, and then I'll go take the truck from them. Then later I thought I might take it to a different shop (who can do a flipping leak down test). Then I would have THEM do the cab off work. The thinking is I don't want to have this shop pull the cab and do the oil cooler and do injectors and either A) have to have another shop pull the cab again to check valves after leak down test or B) I would hate to have them pull everything to check the valves and stuff with practically zero indication that it IS the valves (or at least something on top vs. going out the bottom of the cylinder)

Ya'll are probably a little bit more experienced with dealing with going the cheapest and best route to get things done. The MAIN question really right now is, how bad are those numbers? What would you do with that info? Please answer, I told him I will be calling him before close of business to give him the answer.
 
#17 ·
Dang Crazy,
I wish I had seen that post earlier. I swear I check this constantly and I could have sworn your post was not there before I posted my last one. Once again though, I wish my signature was working. Still haven't figured out why it doesn't show up. But I actually did a painstaking chemical and distilled flush back in November I believe it was and then while doing it I installed a bypass coolant filter kit and switched to ELC. I've known about the oil cooler for a while and wanted to take all preliminary steps before just getting it swapped.

I pretty much agree. Despite the excellent reviews they have and everything I kinda got to the uncomfortable point with them this time. I don't think I'll be going back to them again. Their answers to things don't coincide with the millions and millions of forums I have read over and over on the 6.4. And they sure do seem to point me to the option of not doing work vs doing work.

Right now they are trying to say that I could still get a couple years out of the motor and that if I keep up with maintenance that it could be good for a while. I'm kinda still :doh: because in my mind WE STILL HAVEN'T FIGURED OUT THE PROBLEM!

I'm kind of in limbo right now and their inadequacy is hurting me in the idea that I need a truck to drive and I don't have the time to deal with all of this. At this point I'm wanting to tell them put the lift and tires on and give me the f*#$ing truck back. Theres a shop thats quite a drive but it's supposed to be a top notch diesel shop out in Ft Lupton I believe. I was gonna give them a call and give them the whole scoop and see what they say.

Mainly I feel like theres 2 possibilities right now. The compression is lost out the bottom of the cylinder, or the compression is lost through the valves. My big question is how reliable and useful is the leak down test? Will it definitively point to me valve or ring/cylinder/piston?

With the compression numbers I've given, if it is either of those two problems, how bad is it to be running? The reason I ask is because I am not going to have the time to not have the truck again until about end of May. I'm still hoping for valves, and I can fix it. Rather than just run the truck with my fingers crossed.
 
#18 ·
I've done even more reading... are ALL of my compression readings low?! Other forums I have come across seem to say they all need to be at least around 340??? I just need to know if I need to dump this truck or what the hell is going on...
 
#19 ·
Bueller... Bueller... Please?? I'm still trying to wrap my head around whats going on and I'm giving him an answer monday. I'm leaning towards putting the lift on and just taking the truck and when I can get it to somebody more competent, then get the cab up work done. Washed cylinders is all I can think of for losing compression out the bottom end especially with no extra blow by. I think valves are the most likely but this is an amateur educated guessing.

I think I answered my own question about the compression numbers. Altitude of over 5000 ft = estimated 15% compression loss. Most say 375 is a healthy cylinder at sea level I believe so 375 x .15 = 56.25, 375 - 56.25 = 318.75. Question then is, does the effected cylinder pressure also have an effect on the percentage lost? Meaning that since the variance of psi at this level is lower per % level, then it's easier to read a 5% loss? Who knows.
 
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