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AQ151B/290 Head Gasket leaking on rebuilt Eng ?

D

dearborndeuce

New member
Common prob I realize however everthing is new ( except used head due to corrosion on old one )

All machining done at top rated experienced shop, used head resurfaced & rebuilt w/new guides & seals.
Eng all rebuilt ( had everthing magnafluxed to chk for cracks & all good )

Eng ran perfect for approx 20 hrs and then noticed a hard start ( thinking it might be battery prob )
Chkd everything & found oil level up 1 qt .

Now I know I have a prob as oil can't do that. Water leaked thru to crankcase while sitting .

Exh manifold brand new Barr & no eveidence of water in ports.

Did notice some bubbling in the header tank a few days before & started wondering ?

Removed head & sure enough #1 & #3 show signs of leakage from water jackets into & past cyl seal rings.

Head was surfaced & milled,torqued to factory specs inc the 90 deg pull past the click on the torque wrench.

Anyone with ideas as to why this might have happened ?

Now had the head resurfaced again and have new head gasket.
Before I install I'm looking for expert advice pls so as to prevent same
 
Not sure but maybe the head needed re-tourqeing after use.
Maybe the block needed to be milled? While it's off a piece of glass(usually very flat) or a staright edge on the top of the cylinders??
 
thks J
Had the block chkd at the machine shop before assy & all as new ( original hatch marks still on cyls ) all clearances within specs.

The machine shop ( 50 yrs in bus ) that did the first cyl head work are a diesel specialty shop & the automotive machine shop that rechkd & resurfaced the head this time suggested that the head surface appeared to be a rougher than usual finish ? He ( automotive machinist ) thought a mirror-like finish is what is desireable for these marine aluminum heads. It is now re-surfaced and also spot welded where there were small pitting etc.

I'll re-install this weekend and hope for the best. Using Volvo Penta head gasket ( Wow expensive ! first one was aftermarket but looked same )

Final question re torquing ? I think the spec is 3 stages up to 90ft lbs and then on the final pull, pull thru 90 degs all in sequence as per workshop manual diag.

When & how should the re-tourqing be done ? I presume it should be done on a cold eng ?

Many thks for your input Regards Bob
 
If all work was preformed correct that head is probably cracked. Common for aluminum heads. Sometimes hard to detect at a machine shop because most don't heat them up before pressure test. Good luck
 
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