M96 Engine Project

[wibble]

For the past year or so I have been contemplating rebuilding an M96.1 engine as a side project to my 996 C4. I have been browsing a popular auction site for several months to find a more or less complete engine. To cut the story short I found a complete engine with intermix issues (see my post on same issue https://www.porscheclubgb.com/forum/tm.aspx?m=965335).
It was from an early 996 C2 Tip having done 133K miles. It was overpriced at the 'buy it now' but sat on it a few weeks until the price dropped then made an offer which was accepted.
Whilst many would think complete madness buying a broken engine, you only have to start looking at reconditioned engines and you'll realise the going rate is at least £5K plus in the current market.

So this post will follow the progress of engine strip down, maybe discover some horrors along the way and on to the rebuild with the help of specialists.

 

[andywill]

Tony
A very interesting project wish you all the best an please keep us updated.
Regards Andy

 

[Peter_Bull]

I will look forward to reading this thread and seeing the photos too!

 

[wibble]

Thanks Andy & Peter

First task is to make room in my garage so I can get my car in, so the exhaust system (or scaffolding as I like to call it) needs to come off. Not the easiest tasks at the best of times as previous owner had made an attempt and given up. I was fairly brutal with my angle grinder as the mufflers have seen better days with lots of corrosion around the seams. The exhaust straps were cut at the cat and mufflers removed using 3 bolts either side inside the hangers. The muffler hangers were removed relatively easily.

So the cats have been removed and again an angle grinder and hacksaw were the only option to separate the 3 bolt flange cat to manifold. Literally the nut & bolt had rusted to a 'blob'.

The manifold bolts look to be poor condition - notoriously difficult to remove without sheering. First bolt rounded off with an impact socket and heat applied! So I stepped back and have decided to remover cylinder heads complete with manifolds where I can assess the damage on a bench.

 

[graham.webb]

Great stuff Tony. Having successfully done one already, this should be a doddle....?
Look forward to watching progress!

 

[wibble]

Progress made to earlier post. The top of the engine has been stripped back. This includes inlet manifolds, fuel line & injectors, starter motor, alternator, vacuum lines + AOS, knock sensors, oil fill and dipstick, oil level sensor, oil cooler and wiring loom. The water pump was removed and sheered one bolt. The oil pump to be removed and already one bolt sheered through corrosion. Despite all efforts to soak bolt heads in WD40, you just know that a bolt is about to break just by the feel. Not much can be done about it before it's too late.

The pulse sensor on the bellhousing proved to be difficult to remove despite best efforts. Held in place by a single bolt it simply did not want to come out. In the end had to knock it out with a piece of wood from inside bellhousing dowsed in wd40/silicon spray. Whether this is common, but would not like to attempt this with engine in the car.

From the photo you can see oil stains over bank I (similar on bank II reverse side). This is common as AOS becomes clogged up with residue oil- early tell tail signs that AOS is failing. The RMS looks good, not sure if its been replaced. The IMS housing looks original by the amount of rust. However, it looks like someone has attempted to check it as one bolt is new. I will have fun removing this component, no doubt.

 

[wibble]

Latte anyone? This the intermix oil removed from the engine. The engine holds about 9ltr of oil. I have over 10ltrs here. I had to remove the sump plug with a breaker bar and the filter housing I cannot remove at this point. Makes you wonder who maintained this engine in a previous life.

Sorry for poor light in photo. It was Saturday 9th Nov, heavy rain all day and light was falling.

 

[carreraboy]

Two sugars?

 

[James_M]

Latte anyone? This the intermix oil removed from the engine. The engine holds about 9ltr of oil. I have over 10ltrs here. I had to remove the sump plug with a breaker bar and the filter housing I cannot remove at this point. Makes you wonder who maintained this engine in a previous life.

Sorry for poor light in photo. It was Saturday 9th Nov, heavy rain all day and light was falling.

Wow, what a state. Have you found the cause of the intermix yet Tony?

 

[wibble]

Wow, what a state. Have you found the cause of the intermix yet Tony?

Not yet. If I get time I will remove the cylinder heads before the new year. Usually the issue stems from bank I on cylinder 1.

 

[wibble]

It's been a while, but have started again on the stripdown. Most of the external components have been taken off with just a few coolant pipes and elbow to be taken off the block. The oil filter is stubborn and just will not come off. I expect a new housing will be required because I will have to use brutal force.

Today I scraped and brushed any debri on the top of the engine plus all the years of oil grime. It's an on-going task. It seems the history of this engine was on rural farm tracks and not driven around the streets of Kensington. I tackled bank I cylinder head. All came off relatively easily. The only major concern was the chain guide external fixing had rusted away, so I instead removed the 2nd fixing underside of the flywheel - this was in perfect condition hidden from the elements. I will have to figure out how to remove the rusted fixing later.

The camshaft bearings look good with minimal scratches on the surfaces. This indicated that it had been oil serviced regularly. However, one of the oil passages was blocked with a black gunge - not good. I can only imagine this has come from wear in the chain guides. The vario solenoid was rusted on the exposed casing making it difficult to removed the cover. These solenoids are not cheap, but may have to replace the complete vario units on both sides, if I want to ensure chains, tensioners, cams are within Porsche tolerances.

The 'good news' is I've found the intermix problem. Just like my current car, it has failed in an identical place - hairline crack from spark plug tracking to valve exhaust port 2 on cylinder 1. There is a good chance I can get this repaired by an aluminium specialist. Once I got the head I then had better access to the exhaust bolts. 4 of the 6 came out using a combination of quality hexagonal sockets and twist sockets. The latter shred the heads but they grip stronger as they twist and are ideal on rusty bolts. 2 bolts sheared - not too bad in consideration. Hopefully, I can tackle Bank 2 by the weekend.

The photo shows bank I with cover removed. The inlet cam is uppermost, note the groove on the left hand side facing outwards. This indicates Bank I is TDC and there should be minimal load on the cam nodes when it is lifted away (Bank II will be 180 degrees out until the crank is turned 360 to bring that to TDC). At the far end is a special tool to hold cams in place when cover is removed. The next step was me having to install another tool to hold cams in place that bolts over the cam journels.

 

[wibble]

Further progress made on Bank II. Engine crank rotated 360 degrees so that cylinder 4 is TDC and relieving pressure on cam lobes for removal. No major issues encountered other than the retaining screw for the chain guide had corroded so badly that an allen key would not grip. A neighbour helped with the persuation of a punch and hammer to shock the galvanic bond, and to nudge the screw. It helped the extrator and many hours lost time. However, this does not impact the hours lost chatting to neighbours! 3 sets of neighbours came to investigate and chat - much as I like their interest and tips, failing light on a January afternoon soon expires.

This photo shows Bank II with cover, cams, vario unit and hydraulic tappet valves removed (all numbered and packed safely). Notice the water/oil intermix. The tappet housing needs to be removed to access the 12 head stretch bolts. Cam journals look to be good for 120k mileage.

 

[wibble]

This is Bank II with head removed. The oilway between the stud holes was completely blocked with a black gunge. I can only assume as wear from chain guides. This oilway is a dead-end as the head gasket blocks this purposely - hence the collection of debri. I do not recall this happening on my current engine. Could be attributable to poor service or end of life to the chain guides? I like to emphasise that I change my oil once between normal recommended Porsche intervals regardless of use. I know Porsche have longer service intervals on newer models - you make your own decision.

 

[wibble]

This photo shows the short block. Note the tool to lock TDC at the crankshaft. Not much use now as the whole block will be split at next stage. Still plenty of filth on top of the block right hand side. Having problems removing the coolant housing on the front - all bolts look to be removed, but feels like something is holding it in place. I don't want to force it as this casting looks fragile. Any tips?

 

[wibble]

Side view of Bank I. Cylinder 1 at TDC. Note there were many changes to the engine internals from 3.4 (early 2000) to later 3.6. Some related to liners and piston coatings. Minimal marks on all the liners from what I see visually. Might be interesting to measure ovality of the bores once stripped down and inspected below piston skirts.

 

[wibble]

Side view of Bank II. This time cylinder 4 is moved to TDC. Note the chain guide loosened far left. The oil filter that will not come off bottom right!
The 3.4 had the dual-row chains and considered reliable. This looks to be original IMS by corrosion on housing. Still lots of cleaning to be done on this side.