Need some feedback on a head gasket that failed immediately after replacing it.

[darren1284]

The head gasket failed within about 2-3 minutes. I was following the Bentley torque sequence and running the engine before going to the final angle torque. There was tons of white smoke and the engine stalled. It wouldn't restart and when I checked the dipstick, it was like chocolate milk. I took the valve cover off and there was more thick chocolate milk.

We were replacing the head gasket because my son's 1990 535i (M30 b35) was leaking oil from the head gasket and then started overheating. After sorting through the cooling system, I knew we needed to get the head off. I got it off and took it to a reputable machine shop who went through it and verified it was crack free and resurfaced the head. It took them 5 weeks to get it done because they were so busy and I had them them take the rockers and valves out rather than doing it myself.

I was very meticulous in cleaning the engine block with a plastic razor blade, brake cleaner, and rags. I cleaned the head bolt holes with brake cleaner and cotton swabs and chased the threads. I used new head bolts and a light coat of oil on the threads and head/washer. I used a highend torque wrench.

I have the head off again (thankfully this is an easy engine to get the head off) and getting ready to put a new head gasket on and want to make sure I am successful this time.

Two things I think went wrong. 1. I didn't close the latch that covers the adjusting nut on the torque wrench while doing the 1st level of torque and it slipped to 58 ft lbs instead of 43 ft lbs on a few of the bolts until I caught it. I didn't loosen them up, but waited 20 minutes and tightened the rest to 58 ft lbs.
2. I had mistakenly tightened the throttle cable to take some slack out of it. I was thinking the cable was stretched. When we started the engine at first, we immediately shut it off because I had forgotten to bolt up the exhaust. No white smoke then. When we started it again, the engine was idling very high- like 1700 to 2000 rpms. I was trying to adjust the cable as white smoke was pouring out of the exhaust, but then the engine killed. I wondered if it had hydro locked with coolant getting into the pistons.

Going forward, I am thinking the head should be OK since it hardly even got warm to the touch. I wonder if the head gasket failed because of the slight difference in torque because of the slippage of the setting and the high rpms putting more pressure on the gasket that hasn't gone to final torque. When I removed the head bolts, all looked clean, but the two bolts that got too much torque in the first torque sequence had the thick chocolate milk on them. These are the first two bolts that get tightened at the center of the head.

I hope to just clean everything up, replace the gaskets, and torque it up again making sure the setting doesn't move and keeping the torque consistent. I will make sure it isn't idling high by relieving the tension on the throttle cable. I do wonder if I would be better off skipping the step of running the engine and just do 3 tightening sequences as some have recommended online as opposed to the Bentley 43 ft lbs, 58 ft lbs, run engine for 25 minutes, then torque angle of 35 degrees. I have seen 1st stage 37 ft lbs, 2nd stage 59 ft lbs, and 74 ft lbs as the final torque with a waiting time of 15-20 minutes.

AM I ON THE RIGHT TRACK? ANY SUGGESTIONS?

Also, the head looks good underneath, but area right around the locating dowel is a bit scratched from adjusting the head to seat. Any concerns with that?

Thanks!!!!!

[demetk]

I don't think torque is the issue. Something else is going on. Take a straight edge and feeler gauges to the head and verify it's still flat after the machining.

Did you go over the gasket to fine a leak point?

[darren1284]

It looks like the leak was between cylinders 3 and 4 where the bolts weren't torqued evenly.

[darren1284]

Had the machine shop who surfaced it recheck it with a straight edge and feeler guage and it was all good.

[M4ncyy]

Did you also check the block itself?

[darren1284]

I did check it. I didn't see anything obvious and it looked straight.

I got it back together today and everything seems fine. I used the 3 stage torque method that skips the running of the engine before the final torque stage.

[ross1]

I did check it. I didn't see anything obvious and it looked straight.

I got it back together today and everything seems fine. I used the 3 stage torque method that skips the running of the engine before the final torque stage.

Who told you to do this?

[m735is]

I didn't tell him that, but have done it that way three times (different engines) with no issues. Cough " Haygood" Cough