jdcorbitt3

I have started the tear down and am now prepping for the removal of the engine for repair. It is not as bad as I was initially thought to believe. I was under the impression there was a hole in the case.

It turns out the timing chain hit the valve cover and put a hole in it. It is a three chain engine. I drained the oil and removed the filter. There was no metal in the case oil. There were a few flakes of ferrous metal in the oil filter, nothing I would consider out of the norm. This is an automatic, so I think my IMS bearing is still in tact.

We pulled the engine through and can see the chain rising on the gear as the engine starts to bind. I pulled the cam end covers and can see the cams are not lined up. I therefore, think, somehow the cams jumped time. I am hoping for just bent valves and no piston damage. It came into the shop running, but making a loud rattle. They ran it for a few seconds and shut it down. They said it ran smooth and wasn't missing. I am hoping to replace the valves, guides, chain, and sprockets to repair the engine. Since it will be out of the car, I am also going to replace the IMS bearing.
I will post photos shortly.
Has anyone had something similar in an automatic?

harryrcb

[QUOTE=jdcorbitt3;9207495]
This is an automatic, so I think my IMS bearing is still in tact.

QUOTE]

yup an 04 tip with 33k IMS bearing went. no holes in engine cam timing was still intact but the shaft was damage when the bearing destroyed itself and needs to be replaced which means the motor has to come apart. BTW having a tip trans has nothing to do with the IMS

jdcorbitt3

[quote=harryrcb;9207647]The dealer was implying that a tip trans boxter is not exposed to overreving like a manual gearbox, but everything I have read on the forum implies the harder you run the car, the less likely you are it have an IMS bearing failure.

logray

Yikes.

Macster

Check the scavage pumps -- one in each head -- for any metal debris. If there is any the engine becomes a poorer candidate for an engine rebuild. (My info is that a Porsche tech will inspect the scavage pumps for any signs of debris as part of his engine check out to determine if an engine is rebuildable under warranty.)

If the engine ran and ran smooth with no missing/misfires the valves are not bent.

Best to disassemble the engine and make a full and accurate assessment of its condition.

Automatic (Tip) equipped cars appear to be less inclined to suffer from at least IMS bearing failures but they are not totally immune.

Sincerely,

Macster.

jdcorbitt3

I pulled the scavenge pumps. The back one had the shaft sheared off. It looks like parts of the shaft/blade got between the chain and the gears and that is what blew the hole in the valve cover. I took that pump apart and it looks like a piece of metal got sucked into the pump and wedged in there. I am getting closer to the smoking gun. All I need to do is figure out where the piece of metal, that I don't have, that went into the pump came from.
Other than the metal from the shaft breaking, there was no fragments in either scavenge pump.
I will post photos as soon as I can get them from my iPhone onto the forum.

John

jdcorbitt3

It looks like this guy had the same problem.
https://rennlist.com/forums/boxster-...e-failure.html

I think my smoking gun is the oil pump itself.

John

txhokie4life

BTW, the valve cover is honed to match the head. They are a mated pair.

I'm told you cannot just replace the valve cover.

mike

logray

As it was mentioned earlier, metal or no metal in the sump/oil... in my opinion the OP is doing himself a disservice if he is trying to salvage this engine without doing a complete tear down to at least check for collateral damage - as was suggested by Macster, it's a big gamble for sure if you just bolt on a new head.

I recall a story recently where two guys picked up a busted 996. They found an IMS bearing that exploded, and had to dremel it out. Metal was everywhere before/after. They decided to replace the bearing and clean up the metal particles as best they could, including a mag drain plug and several oil changes, without tearing into the rest of the engine. Well, the car made it down the block and on a short drive and then KABOOM. Had they torn the engine completely apart and cleaned out all of the debris or repaired other collateral damage, would the engine have been saved? They were on a tight budget though, couldn't afford the complete engine teardown/rebuild, and didn't want to sink any more than a grand or so on it, since they only had 5 or 6 invested in the roller (including the busted engine).

And Mike is right, the cam bearing lines will be off on a used (or new) cam cover. Try swapping your bank 1 and bank 2 covers and you'll see what we mean... a used head SHOULD be purchased with it's cover. Just as Porsche does not sell a cam cover by itself without the head.

logray

Also I was shocked (for the better) the other day when I was looking up the prices of a new head from Porsche. For $2500 you get a brand new head, complete with valves, springs, and cover.

Of course, then you need lifters, cams, and the lifter carrier... but still... I was expecting some huge sum of money.

jdcorbitt3

We have started the removal process. I can't see replacing only one head if I go new. It will be a good opportunity to address issues prior to a failure. I would like to build this engine so it will go for a long time after we have used the car and sell it. So many of the parts are really not that expensive like the ims bearing, timing chains, guides and scavenge pumps. $5,000 for a set of heads hurts.

Since it is an auto, I am dropping the engine and transmission together. I understand I will need a special tool to separate the torque converter form the flywheel.

Any comments and suggestions are appreciated.

John

Macster

It is up to you but there is no reason to replace both heads just because one obviously needs replacing. As long as the other head has nothing wrong with it it can be resused.

Replacing any component when it is not necessary is risky for the new component may prove to be defective. The head is a complex assembly made of many components and there's lots of components at risk.

We know there is some concern about this for this is why Porsche offers a 4 year, 50K mile warranty on a new car and offers a 1 year labor, 2 year parts and 24K mile warranty on repair work it does outside of a car's new/CPO warranty.

I read where you are going ahead with the engine rebuild even though a scavage pump apparently suffered some kind of mechanical failure.

You have to be very very sure that there is no metal debris in any passages on the clean side(s) of the engine. All it takes is one to become dislodged when the engine is first fired up and to move to a point where it will block the flow of oil through a critical oil supply hole and the engine's toast, quicker than you can say Oh Cr*p!.

For instance not too long ago in I think the 996 forum someone posted a pic of a 996 engine torn down with a piece of metal in one of the piston oil jets with the result that it was that piston/cylinder that suffered from the lack of sufficient oil.

Sincerely,

Macster.

jdcorbitt3

That is why we decided to tear this engine down. Fear of that one piece of metal floating around. I thought of pulling the plug out of the bottom of the scavenge journal, threading it, and putting a bolt with a screen to prevent debris from getting into the oil pump. This could also be pulled out at every oil change and checked. It would also allow for a better oil change as the risiduel oil could then be drained.

Btw what is the excuse Porsche uses to justify the IMS? The 993 didn't use one, and the new engines don't use one anymore.

John

Stephen Tinker

Possibly because Porsche decided to use identical cylinder heads on the same engine - which requires a drive from the opposite end when you revolve the head 180 deg......
The IMS bearing / shaft just carries the drive to the other end of the engine.

jdcorbitt3

that makes sense. It would cost them less to produce and ballancing the load could then be used as a sales gimic. the service writer told me something like it distributing the torque load more evenly, but I don't buy that, otherwise the turbo engines would have an IMS as well.