Blown out front crank seal on total rebuild


#1

Previously a dynamite pre-70’s master auto mechanic, I decided to rebuild my '88 Nova Hatchback 5-speed single o/h cam beauty of a motor with only 350,000 miles on the odometer. Finished it up over the winter months. Professional machine shop work jobbed out to a local shop, the crank, cylinders, head work all done. So, it ran for 5000 miles, then blew out a front crank seal! Never saw that coming! So, I figured anything could happen and replaced the seal, a painful job at best without removing the engine. Popped that new seal in two days of driving! So, I figure high internal engine pressures must be doing it or possibly some error with the new oil pump/seal/installation or fit. Could a faulty catalytic converter cause high pressure build up? Could an incorrect vacuum hose connection to some one of a million devices under the hood conceivably cause this to happen? Egads, I remember when cars were cars and seals were seals! What gives? I want to get this puppy back on the road before my truck gas bill bankrupts me! And I prefer knowing the cause first, so I can fix that too! Help!


#2

You said one thing that could have caused it, a defective seal. That is, if the new seal you installed did not leak to. If it did I would start suspecting the crankshaft itself. This of course is going o extremes.


#3

The first and easiest thing to check is the PCV. If it is totally clogged for some reason, that could cause the problem that you experienced. And, it is REALLY cheap to replace. If the PCV proves to be functional, then you have to look for other causes that are more difficult to track down.


#4

Well, the totally odd part is that it never leaked any oil at all. The entire seal ‘blew out’, that is, it fell out or was ‘blown out’ of its seating surfaces. I suppose the seal outer diameter is wrong however, the fit seems normal, with the exception that the depth of the seating area seems a tiny bit shallow. I would have expected a deeper recess for the seal. Now that I think about it, I wonder if a seal with an exposed metal outer ring, instead of rubber coated surface would hold in place better. Guess I should buy a replacement seal from the dealer and see if it’s different. The crank was reground and that would have turned up any irregularities…and no, it was not dropped or bumped on the way home from the machine shop. I’m still thinking high internal engine pressures are forcing the entire seal to fall away. Man, it just pours oil after that…I was very lucky to not ruin the entire motor.


#5

Yep, that PCV is really cheap and it was brand-new with the rebuild, before even starting the engine. So, it’s supposed to allow air flow toward the carburettor, right?


#6

It is supposed to carry “blow-by” produced by combustion in the cylinders, and this is routed to somewhere on the intake manifold usually. If it is clogged for some reason, it can allow a lot of pressure to build up in the crankcase–enough pressure to blow out a seal.

I agree with you that a new PCV valve is not likely to be clogged, but–it could be defective. Also, I would suggest that you check the PCV hose if that is the original one. The valve could be good, but the hose could be clogged with old crud.

In the pre-PCV days (prior to '63 if I recall correctly), the “blow-by” was vented to the outside air and you could usually smell old cars coming before you saw them. The PCV was the very first attempt at controlling emissions from cars.


#7

LOL! I appreciate your confidence in my abilities very much however, part me strongly suggests enlisting help when it’s needed! I’m going to check that PCV more closely (thanks vdcdriver) because it seems like it should be a bit more free-flowing than it is. Blowing into it passes air but there seems to be some resistance.

I still think someone out there has more info, equally useful and hopefully will see the post.

And yah, cars haven’t changed much except to bring back ‘innovative’ headlights that turn with the wheels, camshaft variable timing, etc.


#8

The seals with thick, soft rubber coating the outer contact area have given me problems in several applications and I avoid using them. The replacement camshaft seal on mid '90s Escorts was particularly prone of blow out regardless of the care in installation and positive ventilation. Finding a “hard” seal was the solution for the problem.


#9

I think your problem is in the oil pump, it should not allow much pressure on the front seal. I know this isn’t good news because that means a significant tear down to get the oil pump out. BTW, when I put the front seal in a 3AC engine, I used weather strip adhesive to insure it wouldn’t pop out, but that really wasn’t necessary.


#10

Claude, you should know better…Rebuild a '88 Nova with 350K miles?? Why?


#11

C’mon, guys, let’s try to help this guy out. Isn’t that what this forum is about? He’s asking for experiences like his and all he wants is some good, positive advice. I myself can’t offer him advice on this subject as I have never encountered his ‘challenge’. But there are a few other guys and gals that might have. Give him a break with good, constructive possible solutions to his challenge.


#12

It’s a new oil pump (350,000miles) but otherwise I would agree with you. I used adhesive on the replacement seal; just blew out again. Thanks!


#13

Thank you, profhandy. Caddyman has a point so I should say this collaboration between Chevy/Toyota resulted in a truly excellent, yes, excellent, ride! Chevy bodywork for lots of cabin room and Toyota mechanicals for terrific performance, handling and comfort. The 5-speed just teleports me in total comfort. That, and consistent 30+ mpg is hard to beat. The economics of $1000 to $2000 annual maintenance budget just proves the benefit of ownership in the long run. And the crunched up right fender/bumper is a bonus, keeping wannabe racers and aggressive SUVs clear.

Anyway, I truly appreciate the comments from everyone that hopefully will lead to a permanent solution for this great little car. It is a bit frustrating, even embarrassing to have this pesky oil seal issue.


#14

It can only be one of two things: one being faulty parts. Please tell me that, you of all people (An old muscle car man), didn’t use corner convenience store parts! Two, you know there is not enough vacuum to blow that seal out unless there was something drastically wrong with the block - and you would have seen that during rebuild. I think your thoughts about the oil pressure being too high is the right thought


#15

I think your problem is in the oil pump, it should not allow much pressure on the front seal.

I’m not familiar with the oil flow pattern in this engine, but another point to consider might be that a number of oil passages are clogged up or blocked (e.g., wrong head gasket), resulting in too much of the flow (and resulting high pressure) at the seal. This could mean lots of wear already in oil-starved parts, so hope and pray it’s not the case. Hopefully it’s a clogged PCV system allowing too much crankcase pressure to build up, which shouldn’t be too hard to fix.


#16

Um, parts from various specialties; gaskets and seals mostly NAPA. So on Monday, I’ll pick up a seal from the Toyota dealer and the Chevy dealer and see what’s up with that. HIgh oil pressure I can check with a gauge and will install one during the next seal installation. The block is fine. The only thing thing that personally I did not handle was the rings installation, that was done by the shop that did the rebore and supplied new pistons. Geez, am I now faced with blueprinting this bad boy? Like, tearing it down for a complete lower end re-work? Ewww!


#17

There is no oil pressure to speak of on the front seal…There is usually a “slinger” on the nose of the crank to deflect oil away from the seal but that’s to minimize leaks not prevent “blow-outs”…The only thing that would blow out the seal would be massive crankcase pressure buildup.

Try leaving the oil filler cap off for a day or two and see what happens. The PCV should create a slight inflow of air at the cap…If, under hard acceleration it blows oil and vapor out forcefully, you have a major piston ring / blowby problem…


#18

Yep, no slinger on this one; it has a front mount oil pump, the seal, then the pulley. Totally agree with you regarding massive blowby issue, also has one vent to clean air side of filter intake at carb and another one with a PCV attached, so I’m opting for the bad seal/bad installation solution. I checked the PCV valve and hose and flows, all OK. Next time I start it up, I’ll look at these hose outputs from the valve cover.

Hey, supposedly, if I leave the filler cap off, the inside of the hood, the motor, the entire compartment gets coated with slick oil! Then the hot oil vapor gets sucked inside the passenger compartment! If that isn’t enough, if you don’t cover the alternator with waterproof covers during steam cleaning, it shorts out and must be replaced! Oh yeah, I heard about that story over an iced tea…forgot all about who it happened to.

Thanks Caddyman, I’ll work on it a bit more early next month, second weekend!


#19

Did the seal blow out or just the rubber part? If the whole thing came out, you need a new timing chain cover.


#20

The entire seal blew out. But now, I suspect it ‘fell’ out. The first one lasted 5000 miles so it was a huge surprise. The second one lasted less than a couple hundred or so. The seal fits into the oil pump aluminum casting, not a traditional stamped sheet metal chain cover. It’s a Chevy Nova/Toyota Corolla hybrid, 1988. The timing belt cover is plastic, external to any oil galley. Thanks for asking.