Looking for advice on low compression

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peterwells

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Finally got around to reassembling the car and it's back running again. I'll try to keep this brief, ended up removing the passenger side head, but never found a clear cause for the low compression, quite a few of the lifters were bad and I did lap the valves but nothing obvious. Reinstalled head and low compression was gone; haven't repeated the leak off test.

Besides not trusting what the dealer said here are the key things that either worked well or I'd do differently... (i) get a good OBD reader and get what info you can before disassembling (got Forscan only after disassembling), (ii) clean the engine before starting the job (didn't), (iii) take plenty of pictures of wiring harness routing (didn't), (iv) remove radiators (did but only when part way through job), (iv) remove camshaft before pulling head (head + exhaust manifold is heavy enough), (v) made bumpers that allowed aligning the head without damaging the gasket (did- see pictures, high density polythene with some wooden dowels) (vi) in many areas the tape on the wiring harness was in poor shape, looked but never found a really good tape, (vii) you'll need a good impact wrench to torque the pulley bolt on the front of the camshaft, (viii) I used a deep swivel impact socket and a few extensions on the upper of the two large nuts on the exhaust manifold to cat connection, it wasn't particularly tight but difficult to access, (ix) I used a few dozen sandwich sized poly bags to organize fasteners, etc, (x) I numbered the caps that hold the camshafts but didn't allow for them being reversible, (xi) used cardboard boxes to organize items such as timing cover bolts, valve gear (just stab holes in the cardboard to hold items).

Although the car has a lot of miles the engine was not worn, I didn't change the phasers as I wasn't sure I'd found the problem and didn't want to spend an extra $400 on what might turn into spare parts; after running the engine I can hear they're worn so will go ahead and replace while it's all still clean.

It's difficult to justify this job given the age and value of the vehicle however besides the odd bit of cursing I enjoyed the work and if it's reliable for the few years it will have been worth it.

Best wishes for the New Year,

Peter
 

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71Rcode

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Peter, very impressive sir. Did you replace any of the timing components, or roller followers when you were in there? How is she running now?
 
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peterwells

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Thank you, below what was replaced with some additional notes...

(i) On the valve train, the exhaust valves on cylinders 3 and 4 - they had more buildup than the rest but don't think it was needed, the inlet and exhaust springs on cylinders 3 and 4, again doubt it would make a difference but was there, I did carefully inspect the cam followers and all were good, replaced all the hydraulic lifters and all the valve seals, the timing chains, the guides were replaced a couple of years ago, both tensioners (as I nicked the seal surfaces when removing (keep the little retainer things they ship with incase you need to remove in the future), solenoids that control oil flow to the phasers.
(ii) Various single use items, such as head bolts, gaskets, exhaust studs and fasteners, seals for inlet manifold/injectors, etc.
(iii) Oil pump (don't think it was necessary), spark plugs.
(iv) Unrelated work, a hose for the AC had a slow leak so replaced that and the compressor (it was getting weak), the engine radiator (it was beat up)
(v) I thought about replacing the water pump and phasers but they were expensive and straightforward jobs.

I've only put 50 miles on it and the engine feels fine, no obvious leaks, etc. There is the light tick at idle when hot, sounds as though it's the phasers - will check and if confirmed will replace. Beyond that I need to check the transmission fluid level (lost some when replacing radiator) and put oil/refrigerant in the AC system.

While this was a long job, and at times frustrating (trying to understand compression readings) it was generally straightforward.

Peter
 
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