In a jam with a broken cam

[Tbay99Venture]

Yup, the 3400 in our 99 Venture just busted the cam & left my wife stuck about 1 mile from home. I'm puzzled since it never had coolant into the crankcase. I did a LIM some years ago because it looked like it was starting to lose coolant to the outside. Then a year ago I replaced the head gaskets when the front bank started leaking. She said the oil light was NOT lit, at least until it broke down.

So I'll have to dig into it to at least see how seized it is. I know every time I drove it the oil pressure didn't seem to be an issue, at least it came up fast enough to turn off the indicator.

Now I've heard you can't replace the cam in a mini-van without pulling the engine. Every time I've done the LIM I've looked across the lifter valley and it seems possible to come out the wheel / strut area if you lower the engine enough. Possible?

[TGP37]

You could, until you realize the bearings are shot and need replaced.

[Tbay99Venture]

I kind of figured. I haven't gotten it out yet to confirm spun bearings and thought there may be another cause (lifter cracking apart and jamming it, who knows?) I didn't think this was a candidate for sludge, it didn't look bad when I had the heads off. But that was more like 18 months ago not last May as I first thought.

The pressure sender is too far upstream to show if there's blockage to the cam bearings isn't it?

[TGP37]

Oil System for a 3100 L82 60v6. Basically the same except for the most minor of details.

[Tbay99Venture]

Thanks. I'll post a picture if it's interesting. I have a feeling this nothing unique about what I will find.

I know they've been looking to get a write-up about LIM replacement so I figured I'd attack the investigation this way for the sake of step-by-step pictures. Might do the install after the engine is back in for the same reason, though it's a bit more inconvenient. I went ahead and unbolted the balancer pulley as well. I'd been planning to do the front seal and was curious how hard that would be with a breaker bar and no lift. Not a problem after all.

[Tbay99Venture]

Still, no picts? Yes, I am way behind. Should have something eary next week.

[Tbay99Venture]

I got the LIM off and see that cylinder #4's intake valve works but from the exhaust valve on to the end of the cam there is no motion. (Well, I think I've got the valves right, I took a quick look but placed the LIM back and had to head off to work.)

So I guess I won't know much more about why until I pull the thing out. There was no milkshake/pudding gunk anywhere to be seen.

[60dgrzbelow0]

Following on with TGP37's suggestion:

"You could, until you realize the bearings are shot and need replaced."

... about having to pull the engine to replace the cam bearings... these two informative videos follow the current progression of repairs done by you (TeeBay) and the second video illustrates why this will probably be necessary when you see the condition of any of his spun bearings:

Oh... by the way... this web FLV on-the-fly Downloader Add-On for Firefox allows you to easily save all those Youtube videos viewed from time to time (and other similar flv type videos) so that later, you can play these files back from your hard drive using VLC [VideoLan] and either stop-frame or slow-motion view them to get more useful information and NOT have to go back to Youtube to do it!

https://addons.mozilla.org/en-US/firefox/addon/sothink-web-video-downloader/

First he did this...

R&R LIM GM V6

http://www.youtube.com/watch?v=9OKKWqpQzFQ

Then he had to do this...

Complete engine rebuild...

http://www.youtube.com/watch?v=eu1m2wALCIc

The only thing this kid can be faulted for is wearing anything in pants that are made out of plaid (lol) but seriously...his use of PlastiGage during this engine rebuild and the video documentation of these procedures for the lay mechanic are nothing less than video gold!

[Tbay99Venture]

Thanks for those links. And the tip about the plug in.

I didn't get the engine out yesterday -- had only half the weekend to work on it. But it's just waiting for me to hang it from a chain and undo the bell housing bolts. The 3 holding the brace to the diff end of the transaxle are out.

The lifters all had oil but were a bit gummed up in the places where they didn't rub in their guides. I'll have a lot of cleaning to do on them. It will be interesting to see what's in the oil pan & pump pickup.

[Tbay99Venture]

OK the weekend is here. The engine is on a stand and I took the oil pump drive out to confirm the remaining half of the cam cans spin. So once I get the rest of it torn down I can see if it was broken by seized bearings or something else. Looking to the bright side, some bearings, rings, and gaskets should do the job. Oh yeah, a cam. WOT Tech? I'll get some stickers!

[Tbay99Venture]

The bearings on the end look fine



Not so good in the middle



Could this be the cause?



Passages are clear, oil flows, screen isn't clogged.

[3400-95-Modified]

Well the cam bearing could have died due to a LIMG leak which then caused the cam to lock up, but really the main cause is when you break the cam you now have no oil pressure so any duration of running after the break you are destroying bearings so it's hard to tell if the cam broke due to a bad bearing, or if that bad bearing was due to it running with no oil pressure. Was the bad bearing on the side still turning?? or on the end that was not moving anymore... that will give a little insight.

[Tbay99Venture]

Both pieces turned freely before I took them out of the engine. The first machine shop got the bearings out and said the inner ones pushed out with little effort. They were thin. But that shop doesn't line bore cams. I found another shop that will. And some 0.080" oversize bearings are on the way. From my quick look today one of the end bearings looked worn -- it may have been the one at the bell housing end. Tomorrow night I plan to check with calipers and post a picture. (Don't have a ball fitting for the micrometer.)

[NateD4]

I have a spare LA1 3400 block if you are interested. I had one block with the same issue (cam came out in two parts). I wet round and round looking into line boring it. Then I bought another engine and since have decided to go with a 3900 for my project. Thus I have a 3400 SFI block that I'm eventually going to get rid of.

If you are interested PM me.

[TGP37]

You also should check your valves/piston tops. I wouldn't be surprised if a valve or two ended up smacking a piston.

I agree with 3400-95-Modified, LIM gasket leak.

But, I wonder if a clogged oil pump can "hydro lock" if the passages ahead of it were clogged. I've heard of metal pieces locking up oil pumps. I suppose pumping sludge might be enough to break a cam. Like trying to push syrup through a coffee straw.