Bad head again?

Automotive
#1

Hi all,

My son picked up a BMW E39 a few months ago. Turned out it had a bad head. I bought a machened head from an machine shop. Put everything back together and it ran for a whole 30 seconds. Wouldn’t start after that. Fuel PSI was good. Have spark.

Did the first 3 cylinders with a compression test and got 45 60 and 45. I added oil to the 3rd cylinder and it got up to 60.

Should be a minimum of 145 so I’m off by 100 PSI. Is this a head problem or something else?

REALLY frustrated.

Thanks

George

#2

What caused it to have a bad head in the first place? Typically that results from overheating. I’m not super familiar with BMW, but a cursory search suggests USDM M52 engines are iron block with aluminum heads, which would exacerbate warping issues due to overheating.

Obviously, you’ve got no compression on 3 cylinders- what were the other 3 like? Have you taken the head off yet? What shop did you buy the head from? What brand of head gasket did you use? Were the head bolts replaced? Were they installed per the manufacturer’s recommended sequence?

A major multi-cylinder compression loss like that indicates to me a sealing failure at the cylinder head. If the head and block deck weren’t perfectly true, or the installation procedure wasn’t followed correctly, that’d cause that.

#3

How was the block deck prepared for the new gasket? Clean metal everywhere?

#4

I need to complete the test. Got cold and tired.

Bought the car used. seller did not disclose any overheating issue but my son was driving it and started to overheat as he got off the highway. It was consuming coolant and mixing it in the crankcase. Looks like we bought a lemon. or at least an overheated engine.

The original head was removed. The replacement head is still on. Bought the head online from a shop in Florida. Yeah I know. we where trying to save some bucks. New head bolts and a Victor Reinz head gasket kit. Installed per manufacturers recommendation.

Kevin, Yes. the block was cleaned before installation. No left over material.

#5

I’d hope for a faulty compression test setup giving you artificially low numbers and a totally unrelated problem causing your no-start. Thirty seconds is not long enough to overheat and blow another headgasket or head, even if the oil and coolant were totally empty. Although that’s not to say an imperfect deck on the block couldn’t cause this outcome.

At least in any case I wouldn’t stress out trying to figure it out until you finish testing all 6 cylinders. If you don’t find at least one cylinder with higher compression, I’d really be suspicious about the validity of the testing.

#6

Do an wet compression test , if the pressure come up significantly then got bad rings, if not you got bad valves

#7

He said he did that in the opening post.

#8

He only did on the one cylinder , it should really be done on all three as well it should raise across all three I agree with you he need to test the other cylinders as well

1 Like
#9

Thinking about it, the odds of the gasket going bad on 3 cylinders in 30 seconds is absolutely 0. If the compression is really that bad, I doubt it was better 30 seconds of run time earlier, unless your valve timing jumped.

Not that I doubt your knowledge, but that I have seen too many people forget, so I will ask, the compression test was done with the brittle body wide open?

#10

Never underestimate the ability for an improperly-compressed head gasket to burst in a way that doesn’t make sense at first pass. Raggle fraggle third-gen supra

I say there is as yet insufficient data for a meaningful answer. Get a compression test done across all 6 pots and confirm for us the exact procedure you went over to do it, along with the per-cylinder results. Separate wet and dry tests wouldn’t hurt. Right now, we’ve got less than half a complete data set, so everything going on is speculative.

But, to speculate, here’s a list of things that could go wrong considering an overheated M52 with the head swapped:

  • New head’s deck is untrue (poorly machined)
  • Block’s deck is untrue (warped from overheat, differential expansion of head and block)
  • New head has poorly-seated valves (poorly machined)
  • Skipped step in a multi-stage head torque pattern (Always check the factory service manual; disregard Chilton)
  • Cam timing is out following installation (human error)
  • Variable camshaft actuator (if equipped) is out of startup range (incorrect cam profile overlap)
  • Hydraulic lifters have bled down too far (insufficient valve lift)
  • Throttle body closed on testing (insufficient air to compress)

This isn’t comprehensive at all, but they’re all things that have happened to me, or mistakes I’ve made personally.

#11

George,

Would you mind posting the last 7 digits of the VIN?

#12

Don’t underestimate the value of the leak-down test, either.

A more “scientific” approach, just to round it out. I think this guy does a better job of demoing the sound/causes.
also, it’s on a big straight 6, which is always good…

2 Likes
#13

Bv52775

And 20 characters

#14

George,

Can you walk me through the steps you guys took to set up the timing chains & tensioners and the vanos ? I am going to guess that you do not have the associated specialty tools but in either case please elaborate.

#15

Got it to TDC
Put in the lock pin
installed the camlock
removed vanos & sprockets
removed lock pin
Rotate crank 30’
replaced head
torqued to Bently spec 30NM?
then 90 for all bolts
then 90 again
installed the camlock on new head
rotated crank -30’
installed lock pin
Ensured vanos sprocket was installed with full range of motion
installed vanos with vanos timing tool
removed camlock
removed lock pin
rotated engine by hand.

I was getting an error on the new camshaft sensor so removed the vanos valve and there was no oil. So even when it ran for 30 seconds it never pressurized to change the timing.

I pretty much followed the bentley manual for the whole procedure.

2 Likes
#16

when you rotated the engine by hand after assembly did you check that for TDC and the crank and at the cams?

If i were a betting guy - I’d put money on the valve / chain timing being off.

2 Likes
#17

hmm. don’t like that option :smiley:
I rotated the engine by hand but didn’t check anything apart from interference. Did I miss an opportunity?

#18

Hopefully it is the issue and if so it hopefully is not off by much…after you removed the lower chain tensioner - what did you do next? (if you remember - I know these jobs don’t happen in the same day)

#19

Very common to make a error on the timing with the 2.8l inline 6 motor

1 Like