Jammed engine

Hi Folks Just bought a project car with a 'jammed' engine It moves freely just a 1/4 turn using the crank bolt and then stops. There is oil in the sump, water in the system and evidence of compression on turning. Before I remove the motor and strip does anyone have any idea what it is likely to be. The 1/4 turn is I believe the clue, I have no other information Thanks in anticipation. Trevor

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have you tried removing the spark plugs?

Hi Not yet ................but I will tomorrow Thanks for the suggestion

You should be able to turn it over even with compression, if it stops dead and feels mechanically solid, the piston is hitting a valve , could be a snapped cam chain, be careful not to force anything and cause extra damage ok

Most likely a broken rod. If a piston was hitting a valve, you might get more than 1/4-turn, although it�s possible that all pistons could hit valves in each cylinder if the timing is off. If there was a single broken spark plug in a single cylinder, you�d be able to move more than 1/4-turn. An unlikely cause: a faulty transmission. Try pushing the clutch all the way in by wedging something that pins the clutch all the way in and try again. It�s highly unlikely this is the problem, but technically possible. Yes, the transmission turns the gears even when in neutral. I would remove the serpentine belt to make sure it�s not some weird thing with the belt or pulleys or a jammed and stuck-on AC pump.

Hi Thanks for the insight It stops solid and I have not forced it for this very reason.

Hi Thanks for the suggestions I will try all of them and report back

Long shot but maybe a jammed starter, although unlikely Whats the history behind it?

Hi I don't have any history at all bought cold from a third party

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History could also be things the seller may have mentioned. Like it was driving along and saw smoke or heard a rattle then stopped etc. Etc.

Hydrolocked?

Pull the plugs as mentioned above. Then drop the oil pan. That will probably give you a good idea of the issue.

Remove the accessory drive belt and make sure all pulleys turn. Couple years ago someone brought a failed engine to Flat Six and one of the idlers was seized. It stopped the engine from turning.

Not uncommon for seized pulley to cause no turn condition. https://grassrootsmotorsports.com/fo.../126145/page1/

Hi Guys Thanks for all the suggestions still working on them in turn I have no other background on this car I bought it from a guy who bought it from an auction the previous owner was significantly absent So I do not know the lead up to the demise of the engine sadly The rest of the car has been neglected but is remarkably sound All the pulleys turn even just the 1/4 turn is enough to see that although there may still be an issue further round the turn so I will remove the belts next I will post all results as they happen Trevor

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Sometimes those shot in the dark projects end up being a goldmine; but sometimes not...good luck and post pics. I'm sure a bunch of us would be curious to see what you got and how it works out.

Hi folks Finally found time to pull the spark plugs and thick oil/water mixture flowed from cylinders 1 and 6 So it was hydrolocked thanks to all who predicted that. Engine now rotates freely on the starter with no nasty noises I am imagining that it is a cylinder head gasket issue.

Cylinder head gaskets rarely fail on these engines. You have oil on both sides so I suspect the oil came in via the intake. AOS? There are rennlisters far more knowledgeable than I am that can give you potential causes. I suspect you will have to do some additional investigation. Did the other cylinders contain any oil? I would crank the engine without the spark plugs installed and see what it sounds like. Hydolocking leads to bent connecting rods. If you have a failed air oil separator, which to me seems likely, you will need to replace it prior to running the engine.

Next step is to obtain a bore scope to inspect cylinder walls thru spark plug holes, then remove oil sump plate to inspect cylinders from the bottom. Only rotate engine clockwise! Head gaskets never fail once properly installed.

Flush the coolant system out with lots of water and Dawn, you gotta get all that oil away from your rubber hoses or they will be chemically damaged and ALL need replacement. I think there is a way of rigging something up with a hosepipe, others have done it so do some searching on here.

Hi It cranks over just fine with no noises or any untoward issues However I thought that the coolant tank was full and the oil level ok It turns out that the coolant 'level' that i could see was just a false line on the inside of the expansion tank Upon checking with the top off there is no coolant visible. The oil appears to be remarkably clean with no contamination. Oils separator next then 4 of the cylinders are dry and the spark plugs dry and clean as can be seen from the picture Thanks for all the observations and help so far.

If they came out in the order that you have them laid out in the pan it looks like 1 & 3 or 4 & 6? What year is the car?

Hi The car is 2001 They are laid out with the front of the car nearest to the bottom of the picture Thanks Trevor

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FYI I paid �4500 GBP that's around $6000US I guess So not too much of a gamble

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That's a good price IMO, plus you have Hartech over there and they are one of the most competent places on the m96 motor you can find anywhere.

Hi Chris Thanks Trevor

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so 1 - 3

Nice setup, I see a 986 Boxster in the foreground too?

Hi Dan Yes it's a totally original 2000 car never had anything done in any way I also have a 955 too oops!!!!!

If not the AOS, very likely a cracked head. The good new is that head repair is very doable. These guys are experts https://newsite.hamheads.com/ If the oil sump is clean it probably means your main crank bearing are ok too. Good luck with this - keep us appraised...

Hi Is it possible that this much oil/water mixture could come from an AOS failure ? I will keep up the updates, but busy time coming up: Spa Francorchamps, Monza, back to Spa then Imola and finally Le Mans until 17th June. Ho hum work gets in the way of all the fun stuff

Sounds like a blast! I'm guessing D chunk cylinder wall.

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^That^ would affect how the engine cranked no (and probably would have caused CEF)? Didn't he say the engine cranks fine since removing the plugs?... maybe I'm missing something... - wouldn't be the first time...

Because the two “wet” cylinders are separated by a dry one my first thought would be AOS and then cracked head, two places ??

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Good call^^^ certainly more anylitical than mine

Hi Guys Thanks for the continuing input, Engine cranks easily and has no noises whatever, just blew out a little more oil/water mix but not so much. I will add updates when I can Just worked in a free day so will scope the bores and drop the oil sump tomorrow, then off to Spa, working with Proton Competition 2018 Porsche 911 RSR. (well the remaining two anyway).

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Makes total sense to me thank you Trevor

If there is "Milkshake" in the sump then more possibilities, cracked liners (once again 2?), oil cooler/heat exchanger...? Layout and firing order are in post 2 here https://rennlist.com/forums/996-foru...ing-order.html Remember this is US verbiage. Pic is still same orientation.

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Lol. No you are correct.

Hi All Before I left................ Managed to scope the bores nothing obvious but a bit messy. Removed the sump milkshake again Removed the oil cooler (that top bolt is a struggle) Oil in the oil lines but not much Milkshake in the water side. Engine turns freely by hand using the pulleys. Not back for a while now but may fit in one day during the travels !!!! Any further Spa is warm and sunny

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LMFAO, ho-hum. Ok, guy.

So the #77 Am car made pole but #88 was over 3 sec off Should be a good race Sorry we have to travel back tonight....... our work is done Maybe some time in the shop tomorrow though

Now that is a beautiful car!

Well after a longer interval than intended I finally got back into my shop to resume work on the 996 Cab with the previously jammed engine. A brief spell in Shanghai left me with rheumatic fever and subsequently a damaged heart mitral valve, resulting in amazing surgery to repair it and 10 weeks recovery, altogether too much time away from this project but it's all ended well, so no complaints. Now back to the project: Engine now free and turning on the starter motor easily I'm about to compression test it to see what's what, following all the excellent advice and suggestions on this forum. Meanwhile, does anyone know how to ascertain the correct version number of the dash heater control panel for a given car?..... Apparently its on a white label on top of the unit However I do not have the old unit as it was removed before I got the car and did not come with the car. It has been suggested that Porsche may be able to tell me from the VIN no. but that's a tedious process I'm certain. Any ideas???? Thanks Trevor

Glad you are okay now! You may want to try a leak-down test. Good luck and stay well!

Hi Marv Thanks for the kind words I will try that too Nice car of yours BTW

i'm on the road to full recovery now so back to the project car....... So much milkshake in the coolant lines I decided to flush everything out with a hot mix only to find most of it on the sump. Removed the AOS for checking and found a perished diaphragm upon cutting it apart could not fathom exactly how it worked though asI could not see any direct link between oil and water. did a compression test and got the following numbers: cylinder 1- 200psi 2-180 3-185 4-200 5-180 6-190 80psi Leak-down test showed the following 1-4% 2-6% 3-5% 4-12% air escaping from exhaust 5-14% air slowly escaping from inlet 6-4% Decided to pull the engine and see what was going on inside. Upon removing the RH head discovered the following: One core plug was resting gracefully in the cradle of the camshafts having departed it's opening. Not sure why this happens but it's not unique and race engines have threaded plugs. The head appears to be sound and will be pressure tested. The cylinders are as seen in the photos in the next post... there don't appear to be any obvious cracks but however there are 2 almost identical wiggly lines on the 'liner' ,they do not extend to the upper edge of the bore and there is no radial line extending to the outer edge of the liner. I have seen these lines before on a boxster engine subject to a rebuild on the net, but they do not appear to be cracks............any ideas?? I will now pull the other head off to see what I find. I will next crack test with dye the bores just to be sure. Any thoughts would be welcome.... please take a look at the following pictures.......on the next post

Strange line same line different cylinder No. 5 Head core plug fail 5-6 head with gasket cleaned off cyl 6 RH cylinder head with gasket cleaned off no apparent leaks from Gasket as expected The lines in the liners do not extend to the edge and the dark line at the edge/top of the piston is oil/solvent leaking after cleaning not a crack

Higher res picture showing truncated line which does not reach the edge of the liner

Second head now off Same lines but non reach the edge of the liner/bore No apparent cracks in the head So maybe it was just the core/freeze plug all along ?

That looks like a tiny bit of moisture pooled in the bottom. Can you feel a groove?

I'm going to bet on the popped core plug being the root of the problem.. causing a hydrolock situation. with the leakdown #s maybe a few slightly bent valves as a result? good project you have going here.

Hi Thanks for the input That was my first thought as the engine was standing for several months to my knowledge. It does look like a water mark and there is no detectable groove or crack so far...I'm sure the dye will tell me. I can usually feel a couple of thou and theres nothing at all.

I think that's right. the core plug would have caused a mega intermix directly into the sump. I cant detect any bent valves so far but removing them the lap the seats anyway so will find out soon.

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I've seen the freeze plugs pop out of the heads before. It's a documented mode of failure and not unheard of. Like a previous poster said, these engines do not blow head gaskets. With the amount of intermix, I presume you will take the engine completely apart to inspect the bottom end. We have pressure testing plates we use to pressure test the heads and case halves to ensure you don't have any other sources of intermix. We test at 40 psi. The lines in the bores are normal visual aberrations in Alusil and Lokasil bores. I'd be more concerned with checking the bores for ovality and taper while apart and to make sure the piston skirt coating was not damaged on the pistons, as if it did get damaged, the bores will score shortly thereafter putting it back into service.

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Hi Charles, Thank you for taking the time to give me the detailed response, it is very welcome. As I have no history on this car/engine I will tear the whole thing down to see where we are . The bores do appear to be remarkably sound for 90k UK miles Ovality is next on the list of checks. Thanks once again Trevor

Update -ve found 3 cracks in RH 4-6 Cylinder head probably the cause of the lost freeze/core plug. +ve Bores/liners not cracked the dye test appears ok Purchased a sound cylinder head and a low temperature thermostat all for under 1500 USD The original engine has double IMS fitted So...... The rebuild begins Cylinders 5-6 after crack test Lines appear to be generic as Charles suggested 2 cracks allowing the freeze/core plug to fail Third crack in same head....steel core plugs alloy head ???? LH head all good so far That's all for now folks!!!!!!

Quick update on this rebuild................ lapped the valves and found no bent ones so after replacing the stem seals they were all reinstalled Took the opportunity to replace the core/freeze plugs with brass threaded plugs and the ends of the camshafts with similar brass plugs all Loctited in. commenced the rebuild replacing all the gaskets and seals as I went along. Bought a couple of pre=owned dansk boxes and fitted then after updating the flexible sections before they fail. Engine back in now just a few hoses and lines to re-connect tomorrow then fill with fluids and crank over to build up pressures and flush the system. Then drain everything, replace and try a startup Wish me luck ....................... Pictures to follow

Thanks for the update. Were you able to reuse the pistons, (bores were not oval and piston skirts ok) ?

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Hi Folks Well work got in the way again so finally got to restart the engine this weekend!! It fired up with no leaks or problems. Flushed the cooling system twice with detergent so very little contamination left now. Flushed the oil twice and replaced filters both times the Oil looked clean and bright after second flush and the filter was clean too. Fresh oil and filter finally installed, I now have shares in Mobil !!! Replaced Gearbox filter and Oil at the same time. Test run completed successfully then developed a fault..... Starts just fine and runs on 'choke' without any problems. Idles just fine and no warning lights. Press the throttle and release and the engine cuts and will not idle. Hold a few revs on and everything is fine. Then it will not restart without some throttle on. Thoroughly cleaned throttle body ...no change. Suspect MAF so new one on order Update on this later ANY thoughts would be most welcome as usual

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They all measured fine surprisingly !!

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Remove the idle air control valve on the throttle body and clean out the built up carbon in the throttle body and on the valve plunger. Try to test it with a 9V battery.

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Thanks for the advice Is this the case for an e-gas throttle body too? If so where exactly is it located? Trevor

No ICAV (idle control valve) on an E-gas throttle body. The idle is controlled by the ECU/DME.

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No, I thought yours has a throttle cable.

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Thanks for the input but sadly no It's E-gas

Thanks to everyone Well how about that New MAF fixed it 15 $ USD from China 7 day delivery amazing.

Awesome!

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Just for fun I unhooked my MAF and she shook like a crack addict on a serious high! Trippin!