please help-its trying to eat itself!

[cranknrods]

my 6.5 is vibrating at idle really bad after it hits about 200degrees. when everything is cool it idles perfectly. when it gets hot it a start to vibrate really bad no matter what gear im in but it only does it while stoped. as soon as i touch the gas it smoothes right out. could this be timing? my trans was rebuilt about 8 months ago-could it be something in it. but it does it in any gear-even in neutral and park. when it does it-it sounds jst fine from the outside but has almost this deafening harmonic vibration in the truck.im stumped as to what it could be. what happens when the CTS goes out? it doesnt realy sound like a valve train problem-what happens when the rocker retainers fail? maybe engine mounts -but woldnt it happen all the time then?
sorry so many questions but i wanna get this fixed before i have to drive from cali to florida in 3 wks and i dont want to post in the 911 forum when im half way home . any ideas?
(it has a new pmd and injectors)
thanx

 

[cranknrods]

ok-lets see if its timming first but inorder to do this i got some trouble shooting questions.
1st? does the 6.5 have a different idle timming while cold then while hot?
2nd?if so-at what temp does it change or is it progressive?
3rd?does idle timming change as soon as you give it throttle?
4th? what component would go out to all the sudden change my base timming?

if nobody has an answer please feel free to tell me where you would start
thanx

 

[nitrohogg]

the timing is mechanical....what it sounds like to me is a cracked cylinder head, they crack between the valves and you loose compression when it gets warm, first off, is there any niose....um...well, out of the ordinary? when it's running bad is there any blow by? is there pressure building in the cooling system and how hot does it get?

 

[cranknrods]

i thought our timming was electronic, hence the optic sensor to tell the ecu where its currently at? (learn something everyday

hmmm-cracked head, damn! i was hoping it wasnt going to be that. i was kinda thinkin the same thing but convinced myself i was being paranoid. but now that i think about it-it does go through coolant at a rate of about 1/2 gallon every 500 miles and its not leaving a mess on the ground. i havnt had any blow by though and i dont burn any oil. so if it is cracked the crack hasnt spread to the top of the head ---yet...

 

[cranknrods]

anybody got any other ideas before i pull the heads?
and i havnt noticed any pressure in the coolant system and it runs at 200 degrees all day long.
and maybe if someone could give me a nice run down of how the ecu interacts with the ip that would be cool too.
thanx for the reply nitro

 

[highest_vision]

I'm not super familiar with 6.5 electronics, but I believe that they are to some degree electronically timed. Pretty much any diesel will have mechanical timing, but it can be modified electronically. I don't know what a pmd is, if that is what I know as the timing module on the side of the pump (probably not the proper term ) did you take the resistor from your old one and put it in the new? If this is something entirely different, maybe you need to look at the 'timing module.' Something else to think about is a return line restriction. Might be causing enough of a backup at idle to cause problems, but enough fuel gets used above idle. Something else to check. Any check engine light? Had it scanned with a datastream? Might reveal something. Before you go and pull the heads, pull that water manifold and run it, might reveal which head is having problems.
James

 

[nitrohogg]

the PMD or pump mounted driver is what controls the fuel rate, they have two 500 watt resistors and over heat without a good cooler, the diode chip tricks it for more fuel at WOT. I have a number 9 in mine. the PMD is really your throttle cable. the system is fly by wire. what points me to the head is it runs fine till it heats up. I could see a bad CTS causing over fueling if it's still telling the computer it's cold when it's not, but I doubt only one or two cylinders causing his shake at idle.

 

[cranknrods]

well i dont think it is the heads cause today when i was driving i pulled over right when it got to 190 degrees. i sat for a while and waited for the shake to come so that i could track it down. when the shake did come, it did in very short burts. shake 2 sec, smooth 2 seconds, then shake 5 seconds and smooth 3 seconds on and off in progressive increments. on and off repeatedly untill the truck got at about 195-this is where it stays and then the shake was constant. i tracked it down (easier to do when it is cutting on and off) and it sounds like it is coming from the AC compressor. but i have never seen a compressor cause this much vibration-is this normal in a 6.5? it could be that the ac is kicking on and causing more load while at idle causing something else to do the shaking but if that was the case i would imagine that it would shake under any load aplied-such as towing-and it doesnt. what do you guys think?
anyone ever had a AC compressor go bad in one of these things?

 

[towcat]

Firstly,
I don't have a whole lot of background on the Borg tech injection pumps. So anything I say wil be a guess. As far as the AC compressor goes, I would say that I have either had them seize up completely or puke its gasses first. If it is causing the motor to violently shake, the end for the compressor is near but you will be the first i've heard with a compressor dying like that. My suggestion is to have the injection pump checked out first.

 

[holtzer1]

unplug the compressor and try it, if the vibrations gone, you found it. if thats the case, look for loose mounting bolts, both to the compressor and the actual compressor mount to block. yes, i have seen compressors cause bad vibes, and if what your saying stands true...coming and going at a rate of a few seconds...sounds to me the compressor is shot, leaked all the freon out of it and the system is fast cycling.

 

[nitrohogg]

I had a 6.2 that did this and it was the head, but it really started over heating in it's last days. I have had a few vehicles with bad compressors cross my path and have never seen it shake like he says. ungodly noise and a smoked belt is what I've seen in a bad compressor.....but I see things that I haven't seen before everyweek and I'm a full time mechanic that works on everything from lawnmowers to semi's for about 25 years now. we still dunno if there were any service codes......the injectors are new...but that don't mean anything really. I look at the fact that the problem happens when it heats up.

 

[cranknrods]

holt--thats exactly what its doing. even with the ac turned off it sounds like the pump is staying on. the ac system is kinda a black box to me. now i feel dumb for not checking that earlier in the summer when i was ******** about the ac taking so long to cool the truck off.
thaks so much for the help
-looks like im gonna have to put in a compressor real quik before i leave for florida on the 25th
at least its not anything worse-i hope

 

[nitrohogg]

please let us now if that ends up being the problem. I'm would be really amazed if the AC clutch and/or the compressor caused this....

 

[cranknrods]

i just went and picked up a compressor from napa. i got a brand new one for only $244 thats pretty good compared to the usual $500
cant remember who makes it but its not a rebuilt unit. lets see if this fixes it.

 

[highest_vision]

the PMD or pump mounted driver is what controls the fuel rate, they have two 500 watt resistors and over heat without a good cooler, the diode chip tricks it for more fuel at WOT. I have a number 9 in mine. the PMD is really your throttle cable. the system is fly by wire.

Thanks! That tells me a whole lot I didn't know about the electronic 6.5 I guess I was talking about the pmd, but my resistor is apparently a diode. I know that in just one circumstance there was a truck that some shop had before us and what they did I don't know, but they did not put the diode in and it caused problems. It also turned on the MIL.
James