Just picked up a non-running 996; where to begin?

[Bay Arean]

Hi all,

 

This weekend I found a fun new project car -- a 2002 Carrera 996 (non-turbo) with a non-running engine. The previous owner hasn't had it fully diagnosed so it's a mystery (risk) to me! Apparently it died on the freeway with an audible "clunk." PO suspects IMS or camshaft related issues but otherwise has no idea. I want to approach the disassembly in the most logical way possible to diagnose the failure, but I don't understand this engine well yet. How's this for a process flow:

 

1. Drain oil, check for chips/debris, etc

2. Remove oil pan, check for anything obviously loose/damaged

3. Remove camshaft covers and attempt to crank engine using crankshaft nut -- does timing remain intact?

4. Remove transmission, inspect IMS bearing assembly

 

Assuming all that looks OK, what's next? Drop the engine and remove the valve covers?

 

Thanks in advance.

[j_beede]

First thing I would do is acquire a Durametric cable to see if codes were stored. That might give you some insight into how the engine got to its present state.

[Hilux2400]

If you are going to start digging I would give yourself some space and take off: back wheels, back cowl, exhaust heat shields, exhaust silencer boxes, plug sparking plug shields, inner rear alloy bumper bar and air filter box.  With all those off its surprising how much space there is to get at stuff.

 

Best of luck.

 

   

[Bay Arean]

Hi all,

 

I drained the oil and surprisingly there were no chips/shavings to be found. I also removed the oil pan and the oil screen was clear. Unfortunately the view from the oil pan didn't yield any good information; it's just not that good of a view.

 

The PO had removed a camshaft cover to verify that in fact the timing has gone wrong. Cause of incorrect timing is still unknown. Failed IMS bearing, failed IMS shaft?

 

I will next work on removing the transmission, by following one of the many guides on the web! That will give me insight as to whether the IMS bearing has failed.

 

When I inevitably drop the engine, I will want to remove the valve covers (cam covers). Which of these tools do I need for that, and also for re-aligning the timing after the repair?

This $100 set: http://www.amazon.com/Porsche-Camshaft-Alignment-Timing-Tool/dp/B00NAI21OM/ref=sr_1_sc_1?ie=UTF8&qid=1437413014&sr=8-1-spell&keywords=porsche+996+tool+hit

 

Or this $300 set: http://www.amazon.com/Porsche-Boxster-Engine-Timing-Camshaft/dp/B00L0ZOZ0A/ref=sr_1_sc_3?ie=UTF8&qid=1437413014&sr=8-3-spell&keywords=porsche+996+tool+hit

 

I'm not totally clear on the difference between each.

[fpb111]

Get a Bentley Service Manual before you take any more of the engine apart.

http://www.amazon.com/Porsche-Carrera-Type-Service-Manual/dp/0837617103/ref=sr_1_3?s=books&ie=UTF8&qid=1437413883&sr=1-3&keywords=bentley+manual+Porsche

 

The valve covers are also 1/2 of the cam bearings.  If you pull a valve cover you need to support the cams with "clamps" that hold them in place.  To check valve timing you remove the green plugs on the ends of the cam covers (without removing the valve covers) and check the "slots" in the ends of the cams while the flywheel is at top dead center. 

 

The $300 set is more complete.  You might end up needing both tool sets.

[fpb111]

_{Read through this thread}

_{http://www.renntech.org/forums/topic/47831-36-engine-tear-down/}

[Bay Arean]

I went ahead and ordered the $100 set plus a Bentley manual. Every $300 set states "Does not work with 3.6L engines" as AWDGuy pointed out in the other thread. Looks like I'll use the single included "bar" to lock my cams down during valve cover removal.

[fpb111]

That bar is for checking/locking cam timing.  Folks have made cam "clamps" out of wood that work fine.

 

You are right about the other, $300, set not suitable for 3.6 ltr.

Edited July 20, 2015 by fpb111

[Ahsai]

I went ahead and ordered the $100 set plus a Bentley manual. Every $300 set states "Does not work with 3.6L engines" as AWDGuy pointed out in the other thread. Looks like I'll use the single included "bar" to lock my cams down during valve cover removal.

 

I can confirm that the $100 set works fine. I just used it on my 3.6L teardown. On the 3.6L, you just need to lock the crank at TDC #1 before you remove the bank 1 cam cover. There's no need to insert that cam lock tool as the cams are held down by a few bearings that are INSIDE the cam cover. The cams won't fall out if you remove the cam cover, unlike the 3.4L where the cams are actually held down by the cam cover itself hence the need of the locking tool.

[Bay Arean]

 

I went ahead and ordered the $100 set plus a Bentley manual. Every $300 set states "Does not work with 3.6L engines" as AWDGuy pointed out in the other thread. Looks like I'll use the single included "bar" to lock my cams down during valve cover removal.

 

I can confirm that the $100 set works fine. I just used it on my 3.6L teardown. On the 3.6L, you just need to lock the crank at TDC #1 before you remove the bank 1 cam cover. There's no need to insert that cam lock tool as the cams are held down by a few bearings that are INSIDE the cam cover. The cams won't fall out if you remove the cam cover, unlike the 3.4L where the cams are actually held down by the cam cover itself hence the need of the locking tool.

 

Aha! This is news to me. Good news.

 

What's the purpose of locking the crankshaft at TDC? Will this still apply to me since I know my timing is off already?

[JFP in PA]

 

 

I went ahead and ordered the $100 set plus a Bentley manual. Every $300 set states "Does not work with 3.6L engines" as AWDGuy pointed out in the other thread. Looks like I'll use the single included "bar" to lock my cams down during valve cover removal.

 

I can confirm that the $100 set works fine. I just used it on my 3.6L teardown. On the 3.6L, you just need to lock the crank at TDC #1 before you remove the bank 1 cam cover. There's no need to insert that cam lock tool as the cams are held down by a few bearings that are INSIDE the cam cover. The cams won't fall out if you remove the cam cover, unlike the 3.4L where the cams are actually held down by the cam cover itself hence the need of the locking tool.

 

Aha! This is news to me. Good news.

 

What's the purpose of locking the crankshaft at TDC? Will this still apply to me since I know my timing is off already?

 

 

Locking the engine at TDC unloads the valve springs, it is the only crank position where that occurs.  It also prevents the rotating assembly from moving.

[Ahsai]

 

 

 

I went ahead and ordered the $100 set plus a Bentley manual. Every $300 set states "Does not work with 3.6L engines" as AWDGuy pointed out in the other thread. Looks like I'll use the single included "bar" to lock my cams down during valve cover removal.

 

I can confirm that the $100 set works fine. I just used it on my 3.6L teardown. On the 3.6L, you just need to lock the crank at TDC #1 before you remove the bank 1 cam cover. There's no need to insert that cam lock tool as the cams are held down by a few bearings that are INSIDE the cam cover. The cams won't fall out if you remove the cam cover, unlike the 3.4L where the cams are actually held down by the cam cover itself hence the need of the locking tool.

 

Aha! This is news to me. Good news.

 

What's the purpose of locking the crankshaft at TDC? Will this still apply to me since I know my timing is off already?

 

 

Locking the engine at TDC unloads the valve springs, it is the only position where that occurs.

 

 

That is correct. My previous comment assumed (wrongly) that your engine is more or less in time, in which case the cams are not far off from the TDC positions so locking the cams should not be totally necessary just for removal of the cam cover. Once you remove the cam cover, you should not rotate the engine though as the cams will be off some of the cam journals that are cast on the cam cover.

Edited July 20, 2015 by Ahsai

[Bay Arean]

Hi all,

 

Had some interesting updates to the story tonight. I dropped the transmission but haven't yet removed the flywheel, so I can't yet see the IMS bearing. From the glimpse that I have, it looks OK. Surprising.

 

I removed the Oil Suction Pump on both banks. On Bank 1 (driver's side) there was no timing chain attached. Aha! Also, the tab from the pump had broken off and is embedded in the camshaft sprocket.

 

Removing the Bank 2 Oil Suction Pump revealed the chain was still healthily present.

 

Now, a few questions for the experts:

-What was the likely sequence of events? Did the Oil Suction Pump fail first, causing the chain to break?

-Do the cases need to be split to re-install the chain? The small amount of research I did says yes, the case will need to be split.

-Pelican sells chains "without master link." Does this mean I'll route the new chain then use a typical chain press tool to complete the chain?

-Should I plan on getting a cherry picker and engine stand for this work, or can it be done on plywood on the garage floor?

Edited July 23, 2015 by Bay Arean

[Ahsai]

What you removed is one of the scavenge oil pumps. Looks like the pump jammed and that took out the timng chain. Found any metal fragments at the bottom of the engine case or cam cover? You may want to disassemble the pump and check how it looks inside.

Edited July 23, 2015 by Ahsai

[Bay Arean]

Sounds about right. Yep, I'll disassemble the pump tomorrow and see if it's stuck.

 

I drained the oil and it was clean. I also removed the oil pan to check for chip fragments and haven't found anything yet. I haven't taken off the valve cover to check for chips up there. Is it likely the head is destroyed due to loss of oil pressure? I estimate the engine ran for ~10s after the pump failed.

Edited July 23, 2015 by Bay Arean

[Ahsai]

And most likely you will have some bent valves on that bank so I think it makes sense to drop the engine so you can remove the cam cover and the head and check the IMSB as well.

[JFP in PA]

Hi all,

 

Had some interesting updates to the story tonight. I dropped the transmission but haven't yet removed the flywheel, so I can't yet see the IMS bearing. From the glimpse that I have, it looks OK. Surprising.

 

I removed the Oil Suction Pump on both banks. On Bank 1 (driver's side) there was no timing chain attached. Aha! Also, the tab from the pump had broken off and is embedded in the camshaft sprocket.

 

Removing the Bank 2 Oil Suction Pump revealed the chain was still healthily present.

 

Now, a few questions for the experts:

-What was the likely sequence of events? Did the Oil Suction Pump fail first, causing the chain to break?

-Do the cases need to be split to re-install the chain? The small amount of research I did says yes, the case will need to be split.

-Pelican sells chains "without master link." Does this mean I'll route the new chain then use a typical chain press tool to complete the chain?

-Should I plan on getting a cherry picker and engine stand for this work, or can it be done on plywood on the garage floor?

 

As Ahsai has pointe pointed out, you probably have quite a bit of damage and are going to be pulling the heads as well as opening up the cases.  I would plan on getting an engine stand to work on it after you pull it.  As the engine comes out the bottom of the car, a cherry picker will not do you any good except to pick the engine up to put it on the stand.

 

Chains "without a master link" are one piece closed chains, which are much stronger than those with master links. 

[Ahsai]

Sounds about right. Yep, I'll disassemble the pump tomorrow and see if it's stuck.

 

I drained the oil and it was clean. I also removed the oil pan to check for chip fragments and haven't found anything yet. I haven't taken off the valve cover to check for chips up there. Is it likely the head is destroyed due to loss of oil pressure? I estimate the engine ran for ~10s after the pump failed.

 

Second what John said above. In fact, I'm doing exactly that on a 3.6L now that has a lot more damage than yours.

 

The oil pressure is generated by the main oil pump (below the crankshaft pulley) driven off of the IMS at the opposite end of the IMSB. It has nothing to do with the scavenge pump you removed, which is driven off the exhaust cam and is used to scavenge oil accumulated in the bank 1 head back to the sump.

 

As long as there was no low oil pressure warning prior to the engine failure, I could believe that the engine still had sufficient oil pressure. Once the scavenge sump took out the timing chain on bank 1, the engine should stop pretty quickly but if the clutch is still engaged and the car was still moving, the crank would be driven by the transmission and the bank 1 pistons would be hitting the now stationary valves.

[Ahsai]

I think the question now is how to remove the bank 1 cover. Normally you need to turn the engine to TDC overlap cyl #1 position to relieve all the stress on the cams (exerted by the valves) before removing the cam cover since the cams are partially supported by the bearing journals on the cam cover.

 

Check out post #200 in this thread http://rennlist.com/forums/996-forum/853609-blown-engine-14.html

 

Without doing the above, you cannot insert the cam lock tool so the right half of the cams will not be supported in any way once the cam cover is removed. There will be lots of stress on the cams at different ponits and I wonder if you could damage or even break the cams (the cams are hollow). I hope John or other with more knowledge can chime in on this.

 

I imagine you can fab some tools to rotate the cams to the correct positions first before taking off the cam cover but that's a lot of work.

[Bay Arean]

I think the question now is how to remove the bank 1 cover. Normally you need to turn the engine to TDC overlap cyl #1 position to relieve all the stress on the cams (exerted by the valves) before removing the cam cover since the cams are partially supported by the bearing journals on the cam cover.

 

 

Ahsai, if my reading is correct the 3.6L has journal bearings both integral to the cover but also attached to the head. Will the bearing caps in the head not support the camshaft? Scroll up above to what fpb111 said.

 

Alternatively, maybe I could just turn the camshafts manually by hand until they're at a "no stress" point. I assume they'll happily stay there.

[Ahsai]

 

I think the question now is how to remove the bank 1 cover. Normally you need to turn the engine to TDC overlap cyl #1 position to relieve all the stress on the cams (exerted by the valves) before removing the cam cover since the cams are partially supported by the bearing journals on the cam cover.

 

 

Ahsai, if my reading is correct the 3.6L has journal bearings both integral to the cover but also attached to the head. Will the bearing caps in the head not support the camshaft? Scroll up above to what fpb111 said.

 

Alternatively, maybe I could just turn the camshafts manually by hand until they're at a "no stress" point. I assume they'll happily stay there.

 

 

Yes, there are 4 standalone bearings supporting HALF of each cam shaft. Then 4 more journals on the cam cover to support the second half (the right half in the photo below). Yes it you can turn the cams manually, you could bring them to the TDC overlap cyl#1  position.

 

[JFP in PA]

I really do not like removing the cam cover on this engine without a cam retaining tool in place, even though it has some retained bearing caps.  Some people have actually fabricated holding tools from flat stock and some bolts (just be sure not to tighten the bolts into the cam ends too far as there are pressed in plus in the end that you can dislodge).  While this image is for a different engine, it should give you the general idea:

 

 

And here is a home made system in use:

 

[Ahsai]

Hi John, assume the retaining tool is in place but the cams are NOT at TDC, do you think it's OK to back off the CAPs and the retaining tool alternately and slowly to release the pressure? Or we have to rotate the cams to TDC first before undoing the caps and the retaining tool?

[JFP in PA]

Hi John, assume the retaining tool is in place but the cams are NOT at TDC, do you think it's OK to back off the CAPs and the retaining tool alternately and slowly to release the pressure? Or we have to rotate the cams to TDC first before undoing the caps and the retaining tool?

 

With the retainer in place, I would rotate the cams to their TDC position before releasing the caps.  I would also either buy caps (aftermarket tooling) or make them as seen above and install them to help holding the cams in proper alignment before rotating them.  The cams are cast iron, hollow, and there is a lot of spring pressure involved; it is very easy to snap them.  And they ain't cheap.

[Ahsai]

Thanks, John. That makes sense.