engine seizing when warm
 

I've got a 89 928 s4 181,000 miles clean car .purchased on e-bay about 1 1/2 months ago engine seemed to always turn over hard but when running it was fine up until a week ago.When cold it would run fine and idle smooth but as engine temps came up to normal, idle would be erratic and engine would just seize up.If I tried to restart engine it would not turn over,but would be fine once car cooled off.I noticed upper radiator hose was very hot and lower hose was cool,so I replaced thermostat and coolant temp sensor,but same thing.currently I've removed valve covers to check top end and am now going to remove oil pan and bellhousing cover to check for thrust bearing failure but I would think if this was the case it would have issues even when cold.
any ideas would be great,
thanks!

Sounds like heat is causing something to expand too much and lock down the crank. My first thought is torque tube bearing.

Isn't there something about the Thrust Bearing in these Models? Flex Plate, etc?

Assume it is an automatic - and then, yes - classic symptoms of thrust bearing / flex plate.

Over-sized Crank Bearings ?
 

Could the flex-plate side thrust on the crankshaft be sufficient to actually lock up an engine ? It may be difficult to do at this point but perhaps you could contact the previous owner and ask about any work that may have been completed prior to your purchase.

The symptoms you mentioned (worse case scenario) sounds like the crank or rod bearings may have been replaced without properly verifying the oil clearance on the journals. This is just a guess but - an unknown engine that turns freely when cool but seizes up when hot might be the result of someone’s attempt to mask a low oil pressure problem by installing slightly over sized bearings on a standard crank. The typical lack of oil clearance and lock-up would show up after you had reached operating temperature and the engine was shut down.

Would Ebay get involved in a situation like this and provide some assistance ?

Good Luck, Michael :)

Classic Thrust Bearing Failure symptoms. Engine is toast. Sorry.....

thanks for the ideas, but what I don't understand is why it ran fine for the last month?

Sounds like coolant is not circulating through your system. How is the water pump? What is the maintenance history, any?? When was the water pump changed last? What is the oil temp/pressure when this happens? Just some ideas. I am sure others here will have some good ideas. What ever, I would not keep trying to run it until you find out more. You may cause more damage to it. Does the oil pan look liked it may have a new gasket? Any signs of work done on it? Again, any documented service history. Hope you find out and good luck with it.

Save yourself a whole lot of wasting of time and money and look at this thread in detail Just bought a TBF car - Rennlist Discussion Forums
You can join Rennlist free......

I have been substantially involved in the car in that thread, so I do have some experience with your symptoms. Do a search here on Pelican and also on RL for "TBF" and draw your own conclusions.

And yes, the flex plate will force the crank forward far enough long enough to eat the thrust bearing. It will run fine until the counterweights on the crank start to mill the inside of the block. When it gets that far along the engine is TOAST. Can't be repaired with a normal processes or reasonable price. Often the block will crack. Classic failure symptom, engine will run when cold. Will not turn over when warm/hot.

You should check the flex plate for signs of distortion, also there will be aluminum flakes in the oil filter, sometimes in the pan somethimes not...there is a lot written on this problem. Search is your friend. Unfortunately your eBay seller is not your friend.....:eek::eek::eek:

Coolant Temp -
 

Hey Vundba, As others have suggested, it would be best to check the crankshaft side thrust before removing the oil pan to look for any bearing issues. You hadn't mentioned the position of the needle on the temp gauge or your oil pressure - was there any indication of an over temp condition ?

This is NOT a recommendation - but one time a friend had an old Fiat with a similar engine seizure after each hot shut down. He hadn't properly checked his crankshaft bearing clearances during a low budget rebuild. After it stranded him for about the 10th time, his solution was a "Hold My Beer and Watch This" low budget fix for his low budget rebuild ... He held the throttle wide-open after a cold start until the bearings automatically adjusted themselves to allow for the proper oil clearance.....;)

He drove that Fiat for another two years before selling it to his younger brother.

Michael :)

They can be rigged to run for a short period of time with thrust bearing failure.
Hope its not your car's issue. (There is only one other item more crucial than endplay that you need to address --- fuel hoses --- they MUST be replaced if original post-haste --- incredible danger.)

The flexplate load-up / thrust bearing wear issue is serious, recognized and real --- to the enthusiast who studies the 928. Many shops have no clue. Its automatic cars, not 5 speeds, unlike detroit stuff. Cars have shown failure with 40K miles. As time has progressed, it seems more cars are failing.

You need to disassemble the front suspension, remove steering rack, alternator and crossmember to access the pan efficiently. Skip it.

Drop the exhaust a bit, drop the bellhousing cover, remove the pinch bolt and use a tire iron and dial gauge to measure crankshaft endplay (fore/aft). It will be virtually definitive.

You can also cut-up and inspect the inside of that oil filter.


Here is the thread you need next.

My Flexplate - Crank Endplay Check Pictorial - Rennlist Discussion Forums


This is helpful (auxilliary clamp), in the event your endplay is ok ---

My PKlamp Experience - Rennlist Discussion Forums

reading the articles on TBF they talk about prying the flexplate back and forth and seeing it move,but if that is the case how can you have just .007 play.The movement I got was greater than that . I can't easily see that kind of movement.I did get the bellhousing off and after moving the flywheel back the engine did turn over with a screwdriver on the flywheel

They are not prying the flex plate, they are prying the flywheel. I would almost guarantee you have a TBF engine. Sorry about that. Are you sure ebay's insurance won't cover this undisclosed damage? I would seriously look into it as you are faced with replacing the engine or the short block at the very least. Good Luck.

Joe

If I understand correctly the thrust bearing controls for and aft movement, at least according to a mechanic.So if that is the case why counldn't I remachine the bearing seat and make a thrust bearing to fit .I own a machine shop and I have 11 cnc's.My guys say this would be a cake walk in aluminum.All I have to do is strip down the block and put it on one of my cnc mills.Since what everyone is saying about my block now I really don't have anything to lose right?My guys estimate machine time for the recut and making the bearing would take less than 4 hours

you might want to check out My Thrust Bearing has Failed - Rennlist Discussion Forums

Some TBF engines can be saved, it depends on how far the damage has progressed. Sevral people have reported the web in the block behind the TB has cracked, I am not aware of any of those blocks being saved. A couple of people have rebuilt the TB mounting surface by careful and proper welding and remachining...I understand some of the sucess or failure is also dependent upon if the bearing has frozen on the crank and rotated in the block, or not....

Good luck with your repair, I hope you can save it....photos and details of how you do it and what you find when stripping the block would be really nice....

The only ones that machinists have saved were caught before they started to seize.

Its the huge counterweight that is hitting the web inside the engine.

You might want to go to rennlist, to the porsche 928 forum, and pose your questions there.
The reason is there are a series of engine builders and very serious engineers constantly involved on that forum who have direct experience with this issue.
Would be best to confirm with endplay figure first.
You'd be better off trading time on your 11 cnc machines to them for their effort to get you running again.

sounds like a plan! my son and I are getting the underside disassembled so we should have the oil pan off shortly.It's turning out to be a fun father & son project lying under the car and getting him away from his XBOX,considering this is his car(I lost a bet and I wouldn't give him my Porsche so I got him this one) thanks!

Should be a good project, especially if you have the resources to drive it to a conclusion.

My son and I saved an 86, though the work was less involved. Still it was a good collaboration

Endplay measurement is important --- as is checking oil for chips and flecks.

Keep that thread alive over on Rennlist, maybe with some pictures or something, and more engine builder folks will take interest.

Can't wait to get my Son involved in my 928 adventures, but he's not even 4 yet. I keep telling him the Euro is "his" car and in actuality, it will be his. I think an S3 will be our Project in the future.

CNC Services -
 

Hey Vundba, After reading over the worst case thrust bearing discussions, I rechecked the fore/aft flex plate and thrust bearing settings on both my cars. Have you been able to drop the oil pan and take a look at your crankshaft thrust bearing ? If this is your engine seizure problem, hopefully the block can be repaired as you mentioned. Keep us all posted - there may be others with similar block failures sitting around that could use your CNC services.

Good Luck, Michael :)