Engine Failure Facebook Group

[blue2000s]

Originally Posted by Dave S.

This is my first Porsche so bear with me here, but until I was researching this car I had never even heard of an Intermediate Shaft before. I've never had a car or motorcycle with a boxer type engine before, so I assume it's something unique to that design.
From what I've learned on this forum, I was surprised to see the bearing that fails is such a small unit. What function does the IMS perform in the engine?

I've never seen an intermediate shaft used on anything but a Porsche. Someone else will know, but I suspect it may be a remnant of the old VW boxer 4 that started it all.

It's a shaft that spins below the crankshaft and is driven off the crankshaft. It drives a few accessories, and through a set of chains, also drives the camshafts. On the water cooled engines, the intermediate shaft is driven off the crankshaft by a chain as well.

In the most recent engines, Porsche has eliminated the intermediate shaft and drives the camshafts from the crankshaft, as other OHC engines do.

[Bladecutter]

Originally Posted by blue2000s

I've never seen an intermediate shaft used on anything but a Porsche. Someone else will know, but I suspect it may be a remnant of the old VW boxer 4 that started it all.

Actually, I recently learned that the Ford 4.0 SOHC V-6 engine in a lot of Ford Trucks (Ranger Pickup, Explorer, F-150, etc) also has a sort of IMS that drives the camshafts, similar to the Porsche.

Those engines also seems to have fairly high rates of noise and failure.
At least they have noises first to let them know something bad is going on.

They don't actually have an IMS bearing, from the little bit that I've looked into it, however. The problems that they run into are related to the tensioner assemblies failing, causing the camshaft timing to go out of whack, and then pistons meet valves at high speeds, causing massive damage, and big engine replacement dollars spent.

Sometimes, the tensioner assemblies fail in such a way, that the parts punch a hole either into the engine block, or the valve cover assemblies, which then sends shrapnel down into the engine, taking out other important parts.

Not good, either way.

This engine family was originally a pushrod engine, that was modified to accept a cylinder head design that had overhead cams. The original camshaft location in the block was used to house the IMS that feeds the chains to the cams in the cylinder heads. Just an under engineering example.

BC.

[blue2000s]

Originally Posted by Bladecutter

Actually, I recently learned that the Ford 4.0 SOHC V-6 engine in a lot of Ford Trucks (Ranger Pickup, Explorer, F-150, etc) also has a sort of IMS that drives the camshafts, similar to the Porsche.

Those engines also seems to have fairly high rates of noise and failure.
At least they have noises first to let them know something bad is going on.

They don't actually have an IMS bearing, from the little bit that I've looked into it, however. The problems that they run into are related to the tensioner assemblies failing, causing the camshaft timing to go out of whack, and then pistons meet valves at high speeds, causing massive damage, and big engine replacement dollars spent.

Sometimes, the tensioner assemblies fail in such a way, that the parts punch a hole either into the engine block, or the valve cover assemblies, which then sends shrapnel down into the engine, taking out other important parts.

Not good, either way.

This engine family was originally a pushrod engine, that was modified to accept a cylinder head design that had overhead cams. The original camshaft location in the block was used to house the IMS that feeds the chains to the cams in the cylinder heads. Just an under engineering example.

BC.

That's a good point, OHV engines drive the pushrods through intermediate shafts (or more correctly, the cam). The unusual thing about the M96 is that the engine was designed as OHC from the beginning and Porsche still chose to use one.

[tonycarreon]

Originally Posted by Bladecutter

Actually, I recently learned that the Ford 4.0 SOHC V-6 engine in a lot of Ford Trucks (Ranger Pickup, Explorer, F-150, etc) also has a sort of IMS that drives the camshafts, similar to the Porsche.

nice. maybe i'll start taking bets to see which goes first - my ford or my porsche.

[dennis]

OK. I have an '01 Boxster with 34k original on it. I guess I am in the group that should worry based on year and such low mileage? Is there a mileage cutoff where say, after a certain ballpark miles the issues lessen? Most of these post suggest the IMS failures occur at fairly low miles

[mts]

Dennis - I don't beleive anyone has been able to make a direct link between mileage and failure (except maybe Porsche and if they have they aren't sharing). PM me your email address and I will email you a copy of the June 2010 Excellence Magazine article that my help shed some light on some of your questions.

[brabus]

Originally Posted by mts

Dennis - I don't beleive anyone has been able to make a direct link between mileage and failure (except maybe Porsche and if they have they aren't sharing). PM me your email address and I will email you a copy of the June 2010 Excellence Magazine article that my help shed some light on some of your questions.

Hi sir,
Can you also PM me a copy of the Excellence Magazine article , really like to read more about this .

thanks in advance

[jcb986]

coreseller...feed that mut will you. Oh, he's a drug sniffing dog. Send me a dozen of those, please.