I just finished putting my LB7 back together with head gaskets and ARP studs I thought all was well I took my time and it is still pressurizing the cooling system upon start up, can anyone suggest what went wrong ? I torqued them in three steps let sit over night went back over it and torqued to what ARP said 125 ft lbs any ideas? is that the right torque ? or what to check ??
headstuds and gaskets still pressure in cooling ,..HELP
- Thread starter merlot
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Maybe a injector cup leaking? Did you have the heads checked out before reinstalling them? Pitting around we're the injector cup seals is a common problem on these motors.
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I had the heads decked ,cleaned and a vac tested for the valves sealing I was talked out of pressure testing them , the injector cups were like new no pits at all,installed new O rings on them and put them in I torqued the injectors to specs as far as I know its right its a 04 LB7 is there any tricks to installing the cups ?
I was told it may just be air bound (boiling to steam) but it seems excessive for that anyone know the best way to bleed a 04 LB7 ?...It pressurized within 3-4 min. and when the cap was removed in 3-4 minutes time it blew out all over and when removed it had a steady flow of air coming out bubbling out of the tank
Sounds bad
It sure sounds like it has pressure. Did you loctite the injectors and tq them one at a time? If the loctite setup and then youtq them it could do what hours is doing.
It sure sounds like it has pressure. Did you loctite the injectors and tq them one at a time? If the loctite setup and then youtq them it could do what hours is doing.
did you check the deck on the block with a straight edge? Have only seen a few that required the block to be decked to true it up.
Arp's PDF but they tell you only 1 cycle of 60-90-125 with new lube.
http://arpinstructions.com/instructions/230-4201.pdf
I still tell everyone to use what has worked over the years. 60-90-125, back off a little 60-90-125 and repeat one last time 60-90-125 for the M12 studs. The M8 10-15-25,10-15-25 and 1 more time. Then leave overnight for heads to cycle temp change overnight and then go across the M12's at 125 some find a few that retq again and just hit the M8's for the hell of it at 25.
Also check to make sure the head gaskets are on the right sides there needed on. I have had a few customers mix this up and it will cause the same issues.
Right side
Will show a R on front side of head for Right side. Also the punch outs will show grade and side that's at the back of head.
The top slot with a lower punch is grade C and the lower slot with punch to top is Right side.
Left side
Will show a L on rear side of head for Left side. Also the punch outs will show grade and side that's at the front of head.
The top slot with a lower punch is grade C and the lower slot with punch to bottom is Left side.
The injector cups once loctite is on should go right in and install injector. Tq them to spec and leave for 24hrs before starting up.
ok it sounds funny to ask maybe but are you saying to loctite the injector cup cone at the head where it seals or the bolt holding it ? and what loctite strength (color) is recommended ? I did neither and its my first duramax head job and I had no help on what tricks and such to do so if i'm taking it apart again i may as well get it right this time LOL
Yes you must add loctite around the seating surface of the cup. That's the reason you need to install the injector and tq the bolt to help the cup seal right. You want to use Red but some have used a green I think it is. You do not need to remove heads just pull the cups back out. I had told you this on the phone when you asked about replacing the cups with all new ones. And you had asked how to remove them from the heads.
thanks Henry I had forgotten what you said days later on install
LOL I used red high temp Permatex brand Napa # 765-2680 and cleaned everything good using a 1 1/4 nylon brush with carb cleaner and made my own injector cup remover that worked perfectly out of a 7/8 aluminum cement lag ground it to fit just a little and a 3 inch lag bolt ....all is well runs Great and no pressurized cooling system :thumb: and as a foot note I torqued the heads in 3 steps to the LB7 ARP head stud specs of 125 ft lbs let sit over night and torqued again I got a little out of the center bolts mostly (using ARP's new lube) ran it through a good heat cycle and since I had to take it apart again to seat my # 6 cup pressurizing the cooling system I checked the torque on the head bolt/studs they were fine they took nothing more at all ...
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