_Ish

This post is basically a long winded story about how I have no oil pressure and a very upset rod bearing. Questions are at the end, but I figure context might be useful.

Many moons ago.... Probably about 8 moons. Last October. I decided to take my 944 up to school, about an hour drive. Car drove fine, no issues with the gauges or any weird sounds. I might have been a little hard on it once or twice, but nothing too crazy. I parked on the top floor of the parking deck, went to class for maybe about 4 hours, and then came up with silly little idea that I should drive home. Unfortunately, the 944 didn't seem to agree with that idea. I started it up, and was met with the big ol' light in the center of the dash. No oil pressure to speak of. Stayed right at zero, the needle didn't even bounce. First theory was that the sensor was just being temperamental, but the engine sounded clunkier than usual, so I'm gonna say the gauge was fine. Theory two was that there was some issue with the pump losing prime and it needed a few seconds to build pressure. I gave it about thirty before I got spooked and shut it off. I tried one more time, gave it a few more seconds, and then shut it off again. Still no oil pressure.


Google did not provide a solution

I got a tow home (on my dads trailer, tow trucks are too expensive for my taste), and tried a few things. I went ahead the swapped the OPRV for another one I had lying around, started it again, but still no luck building pressure. I pulled the filter and cranked the engine to see if any oil was even making it that far, but no luck there either. At this point I figured that the pickup tube might be broken, maybe some issue with the oil pump, not sure. I got busy with school and some other projects, and I really didn't want to go through the trouble of pulling the pan. I let it sit for a while, until last week. Now that school is over for a while, I got a spark of inspiration and got back to working on the 944. Got the pan off, took the pickup tube off, but I didn't see any cracks or hear any leaks when I put some air pressure on it. I pulled the pump off too, but didn't see anything there either. It was time for a timing belt anyway so the pump wasn't too much extra work. Now I've been in the process of putting things back together, checking everything as I go along. Still not certain about the reason for the loss of oil pressure. My working theory is that after I removed the power steering pulley, maybe that somehow resulted in less pressure on the oil drive gear. I did torque the crank bolt to 155 ft.lb., but maybe it needed that thickness there to put enough pressure on the drive gear. Anyone know if the manual steering cars had a different spacer on the crank bolt? I went ahead added a spacer when I put the crank bolt back on just to be sure, but won't know if that made a difference until everything is back together.

I did notice some metal shavings in the oil so I figured now would be a good time to check the rod bearings, go ahead and swap them while I'm in there. Here's the cut open filter. Not super pretty. The oil isn't high on mileage, but I do suppose its pretty old at this point.

Metal Flakes, part of a nutritious breakfast

Now comes to the main attraction. I pulled the number two rod cap first and OUCH. I haven't really seen what failed rod bearings look like, but this seems particularly rough to me. I count 7 pieces. I'm clearly no expert but I think there should only be two. The craziest part of this to me, the rod journal looks fine. Not flawless, but no gouges I can feel with my fingernail, and its smooth to the touch. I'm amazed its not absolutely ruined.

Crunch

It looks better in person than the picture. That's smudged oil on the bottom left, there's really no major damage.

So that brings me to where I am now. That's the number two bearing. Number three looks fine, I haven't checked the others yet. I'm going to put some new rod bearings in and just run it until it fails again or I have some other reason to pull the engine. I'll check it with some plasticgauge to make sure its still within spec, but I'm definitely not pulling the engine right now.

So I suppose the main question I have for the fine people of Rennlist is whether or not the rod bearing could be some cause of the oil pressure issue or just a symptom. A nicely timed coincidence maybe? Any other ideas about what might have caused the oil pressure problem? I appreciate any help or advice, I've provided about all the info I have to go on. I'll update with a reply if/when I find anything else.


P.S. I know the pictures are huge but I can't figure out how to make them smaller. Help on that would be nice too.

jhowell371

Wow, new one on me.

924RACR

Oh, that's pretty bad dude.

No, I would NOT just slap new bearings in it and give it a try. Save yourself the trouble and throw the new bearings in the trash, 'cause that's where they're headed.

Bare minimum, that crank journal needs to be polished - assuming it's still in spec for original size bearing. Might need to be reground to the next smaller size; need to check with a micrometer to know. Other rod bearings probably also have damage, or contamination - the latter which could also easily extend to the mains.

You need a full tear-down and rebuild, at least the bottom end... and there's no point not throwing new rings in it as well (after running a dingle-ball hone through the cylinders to rough them up to break in new rings) while the pistons are out. Do a valve job too, probably just need to re-lap them in to ensure full sealing again.

You ARE pulling the engine right now. The only question is how much time and money you waste figuring that out, how much more damage you will cause along the way.

If you've never seen this kind of failure before - and I've seen a LOT, racing - you definitely are not qualified/experienced enough to decide if that crank etc are good as is.

walfreyydo

The issue is that youll also need to inspect/replace your main bearings, since those are also affected by no oil pressure. I wonder what those look like...

To answer your question, its hard to say whether the rod bearing was the symptom or the cause. I would not expect a bearing would break into pieces (assuming it did not happen during removal) just from running the car with low oil pressure for 30 seconds. If the bearing was broken previously, it would not be seated snuggly against the rod journal and would likely not create the resistance needed to keep oil pressure high, thereby potentially reducing your oil pressure. There could also be clues on the main crank bearings once you get in there.

Unfortunately the motor will need to be pulled and all bearings replaced and journals inspected, at a minimum. A "refreshed" used motor may be your best option, depending on what you find.

Zirconocene

This situation sucks, sorry to hear about it. I have nothing to add about the wrenching but will just say:

A) Leave the pictures big, it's nice to be able to get some detail.

2) I dig the captions

3) Maybe it's time for a GM 3800 V6 (I kid, unless you're into that)

Good luck

tempest411

This is the sort of failure that sends shivers down my spine; a failure without any appearant cause, and these engines are GREAT for that.

Theoretically, NA engines don't make enough power to damage themselves no matter what you do to them, but here we are.

T&T Racing

Definitely bad, the #2 crankshaft connecting rod journal is not OK. Wasting money if thinking that journal is OK
Need to balance a used good crankshaft vs machine your crankshaft. If #2 connecting rod bearing failed, was this car tracked?

tempest411

Undersized bearings for these engines are absurdly expensive. It's a shame the aftermarket never stepped up with any offerings.

_Ish

Alrighty, I bring information and many comments to respond to. Comments first.
T&T Racing - Never tracked. I drive (drove) this car more gently than anything I own because I'm scared of breaking it. That being said, I was much harder on it than usual the day I had the oil pressure problem. Excited to drive it in some nice weather I suppose. Back tires broke loose in second gear while making a turn. First time I've done that in the 944. Like I said, before then I have stayed very gentile.
924RACR - I have seen failed rod bearings, but not one that completely shattered itself is what I meant. Not broken on removal, cap came off and it was like that. That's not to say I have enough experience to be certain about my next steps.

I agree that putting a new bearing in is not a permanent fix and is going to fail pretty quickly, but I have a reason to ignore my better judgement and everyone else's. For now anyway. The 944 is not my main project car at the moment. It's not really even my main project 944. I'm in the middle of building a 2.3l Turbo Ford engine, and that's sucking up all the car budget. But the 944 is in the driveway, and needs to be moved in short order. That means I have to put it back together, running or not, so I can at least move it around. So if it has to be put back together, I might as well put bearings in it so I can maybe drive it a little on the weekends, at the very least move it around the yard. The alternative is that I lightly bolt it back together so its less work when I go to pull the engine, and park it in the back yard for the foreseeable future. Probably until next year.

I'm well aware the new bearing will fall apart in short order, but I'm not sure how short of order it will be. 100 miles? 1,000 miles? 10,000 miles? 1 mile? I genuinely have no idea. I would be absolutely ecstatic if I can just drive it for another thousand before I have to pull the engine. I'd love to hear your best guesses. Winner gets a hat. (Not from me, but they're welcome to buy one. Also, the odometer is broken, so the winner will be chosen at random.)


This is the current workshop. I have a rug to keep the gravel away. The garage isn't mine to use, and definitely has no room for a car even if it was. I am but a wee young lad, and am living with my parents until I finish college.

So here is what I bring to the table to defend my decision to just put some bearings back in. Here are bearings 2 and 3 cleaned off a bit, as well as the corresponding rod journals. I also got a picture with a little digital microscope.


Rod 2 crank journal

Rod 3 crank journal

Rod 3 rod bearing, beside new ones


Rod Journal 2 under a microscope. I actually won 2 silver medals in gymnastics in the process of taking a picture with a microscope under the car.


Rod Journal 3 under a microscope

Please note, none of it is great. But I'm sure there are a lot of cars driving around with worse. I'm just going to assume that the mains are similar to rod 3. I measured both rod journals at various angles several times with a micrometer. Number 2 came out to 2.0471" (51.996mm), number 3 was 2.0472 (51.998mm). That's to my untrained eye on the Vernier scale anyway. Some of you may note that is outside of the spec (51.971mm - 51.990mm), actually larger than it should be. I'm going to mark that up to the car sitting in 100 degree weather all day while the mic was in an air conditioned garage. User error is could definitely be a factor. Maybe the mic isn't calibrated or something. That being said, they were consistent across several measurements, which at least tells me that number 2 didn't get significantly more worn than number 3. Clearance between the bearing and the rod journal, based on plasticgauge, came out to be ~0.038mm. That's within the spec (0.034mm-0.092mm), but the temperature issue still applies to the crank and the new bearings, so maybe not as tight as it seems.

Now, I agree polishing would be very good. But I really don't have the time or money to pull and rebuild the engine right now. I'm not broke, but I'm sticking to my annual project car budget. I may try and run some polishing cloth over the journal it by hand while its in the engine. Some of you may think that sounds very stupid. I think so too. Even so, maybe its better than nothing? Might knock the edge off? Maybe? Possibly? Not sure. I also plan to go ahead and run a few quarts of oil through it. I have a weed sprayer full of oil hooked to the filter outlet, so I can push oil through the engine without it running. Hopefully that might help get any particles out, but I can't imagine too much made it past the filter.

I don't mean to offend anyone by putting it back together as is, even after everyone agrees that its a bad plan. I know many of you know a lot more than me about these cars and rebuilding engines. It just seems like a temporary fix until I can take a better route. I'm not particularly worrying about ruining anything except the block; I have a spare crank, head, cam housing, etc, etc. I pulled an entire blown engine (timing belt failure) apart and kept whatever wasn't ruined. Block was cracked, it, the pistons, and the valves were the only things lost.

If all of that still screams "This engine is going to shred itself the first time its started," I will surrender, bolt the car back together and roll it off into a field until next summer. And really, give your estimates on how long the engine would last. I'm not looking for another 100,000 miles. 1,000 would be nice. Thanks for the help.

Autobreza

@_Ish I completely agree with your decision, especially given the constraints you have to live within. I've done "questionable" repairs were required which were sometimes successful and other times not so successful. Either way it's your decision and we'll provide the best advice possible for your decision.

You need to determine the root cause of ZERO oil pressure.
Were the hydraulic lifters noisy from the low/no oil pressure?
Does this engine have a history of a failed oil heat exchanger?
Do replace the main bearings as they are probably toasted as well.

Rennlisters will have more constructive and diagnostic suggestions.

DHS928

Well if you are going for it and putting it back in service, Put really good oil in it (synthtic) and really limit your RPM's at shift points so you keep the RPM's down. If on first crank up you have good oil pressure you could get a fair distance out of the engine. Start watching eBay for good parts and stach them away so you can just swap out when the time comes. You might teach us all something! Good Luck!

walfreyydo

I say go for it, what do you have to lose? I didnt think those journals looked horrible horrible.

Nowanker

Ordinarily, I'm a do it once, do it right devotee.
But I'd run that crank, and not worry too much about it...
Probably limit the RPM tho.

My biggest concern would be for the mains.
Logic says the rod bearings give up first (bigger load, lower in the lubrication chain), but that's not always the case.
I bought a low time engine that was assembled with the plain shells installed in the case instead of the girdle, severely limiting oil flow.
Rod bearings were cherry, main bearings were absolutely fried.
Along with the main journals...
Good luck, let us know how you go!

fwb42

Ish, Please, please put proper blocks under the front tires. Unstable gravel + narrow blocks could lead to you not ever finishing this repair.

_Ish

Autobreza - I've never noticed any issues with the heat exchanger. Coolant and oil looked normal. Maybe the bearing material plugged it up, that's a decent theory (It's before the filter right?). I might just pull it off while I have everything out of the way to be sure. I'm not sure about the lifters, I didn't really get in there and listen while it was running with no oil pressure. It was definitely noisier than usual, but no way to say if that was the rod bearing or the lifters, probably both.

DHS928 - I have been using Mobil 1 Advanced Full Synthetic 15W-50 since I got the car. Not sure if its a good choice, just what I've been using. And like I said, plenty of parts laying around for whenever I get to them.

Nowanker - There isn't really a way to get the mains out of the car with the engine still in it. The bottom half maybe, if I just drop the girdle. I'd rather do neither than only half, but I can at least check the journals.

fwb42 - No worries, there isn't any weight on them. Since I have the subframe out, I just put some blocks under the tires to keep them from flopping back in and getting in the way. Jack stands are whats actually holding the car up.


As to my current theories with the oil pressure, there are really only a few things it could've been. Oil didn't pump out of the oil filter hole with the filter removed. That means either: 1.) something was blocking the oil passages, 2.) the pump wasn't spinning, or 3.) the pump had lost prime.

1.) Heat exchanger plugged with bearing material might make sense. How fine are the channels in the exchanger? Could it be blocked by stuff that made it past the pickup tube screen? I should have checked it before I put the oil pump and timing belt back on, but I didn't think about it. All the other passages seem large enough that they wouldn't be blocked. I know for certain it isn't blocked between the pickup tube and the pump.
2.) I am fairly certain I torqued the crank bolt properly. I have the flywheel lock and use it regularly. On the off chance I never torqued it, I can at least be sure I did this time, so that variable is eliminated.
3.) As for losing prime, maybe? I could the spun bearing cause it to lose prime while sitting? I don't think so, but maybe I'm wrong. I know the OPRV could allow that, so that variable is eliminated too now that I swapped it. Even so, I would've thought it would regain prime after a few seconds.