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Old 07-03-2010, 12:46 AM   #1
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Keep the bus? Or too many problems?

Hi All,

We recently bought a 1989 GMC School Bus for really cheap ($700). It has 270,000 miles on it, with a 6.2L diesel engine and a TH475 3-speed trans. Itís a short bus, and weíve stripped the seats and floor in preparation for converting it to a comfy living space. The body, tires, and electrics are in great shape.

When we bought it, it wouldnít start. We got it running (FSO solenoid) and fixed the brakes (hole in brake hose from MC). Then we took it to a diesel mechanic. Their diagnosis follows:
Excessive crankcase blowby
Excessive smoke under load
Major oil leaks - dripping on the ground
Middle U-joint is bad
Both king pins are marginal

At the moment, the bus drives fine. We are trying to figure out if we should keep it, or if we should look for another bus with fewer miles and better maintenance. We are on a tight budget, so we would much rather have a $700 bus than a $2500+ bus, but we also donít want to sink our money and time into a bus that wonít survive very long.

Do folks think this bus is going to self-destruct within the next 50,000 miles? Have we reached the end of life for this engine and possibly transmission, or if we keep maintaining things, should it last a lot longer?

For those who are interested, weíll post some more details about the state of the bus and our questions below.

Thanks so much folks.

Aaron
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Old 07-03-2010, 12:47 AM   #2
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Re: Keep the bus? Or too many problems?

More detailed explanation of the issues:

When I asked the mechanic to quantify the blowby problem, he just said it means that the engine isnít as strong as it could be, and it will gradually lose power over time. Since it starts cold just fine and can pull 55mph, as I understand the problem, it canít be too bad now...but will it get worse soon?

Weíve noticed a fair bit of smoke when starting up from a stop, but not a horribly excessive amount. We havenít seen smoke issues when itís idling/cruising.

The transmission leak appears to either be the pan gasket or where the gear selector linkage goes into the trans. Itís enough of a leak that thereís maybe two to four large drops of red fluid per 24 hrs if we put cardboard under it.

I think I have traced the engine oil leak to the valve cover gaskets. There is clearly oil leaking from the bottom edges of the valve cover gaskets, enough that fresh oil accumulates on the exhaust headers after a day of sitting. Iím not sure how much it leaks, as far as actual volume though, and I guess anything below the valve cover gaskets could also be leaking and I wouldnít be able to tell due to the oil coming from above. The valve cover gaskets look like a real pain to change, and the driverís footwell gets in the way of accessing anything around the driverís side valve cover. But with that much leaking should we try and do it anyway?

Iím currently researching how to fix the U joints on our own. Iíd probably do this under the bus, since thereís reasonable clearance under there and Iíd rather not pull the whole shaft.

I donít really even know where the king pins are besides in the front steering/suspension and that Iíd have to jack the bus up to replace them.
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Old 07-03-2010, 07:10 AM   #3
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Re: Keep the bus? Or too many problems?

You are the best person to judge you mechanical abilities.

We replaced u joints in Ĺ hour in a parking lot while on a field trip Ė I think you would want to pull the shaft- we did.

No idea on the kingpin but here is link to a write up that will at least give you an idea of what it involved Ė note that the author states in for school bus it must be reamed to properly fit new king pins.

http://www.stovebolt.com/techtips/kingpin.pdf

IMHO you need to sort out a decision about your motor before you fix the KP/Unis
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Old 07-03-2010, 11:22 AM   #4
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Re: Keep the bus? Or too many problems?

drive it!, if the rest of the bus is in good shape, to your thing with it, get a cost to dothe king pins, price out a engine(used) and tranny, over time and as you can aford to do it get the stuff done, it might be 1 or 2 years before your motor goes, as long as you can use it the way it is now, I would check into the king pins as soon as you can, bit of a saftey thing there.

but with that being said, its totaly up to you and what u feel best with

thats just my 2 cents(canadian) 1.4(us)

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Old 07-03-2010, 01:05 PM   #5
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Re: Keep the bus? Or too many problems?

I know Idaho Motor Pool had a bunch of 6.2Ls for $250 each not too long ago, still in the crate (military steel container & sealed). The 6.2s are cheap enough to find just about anywhere. But if you want more power (think Tim-The-Tool-Man-Taylor) look at a 6.5L. They are becoming cheap as well. The 6.2 is easy to fix and maintain. I have four of them and love them. Just don't over rev the engine and they'll last forever. Over rev and they'll burn up quick.
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Old 07-06-2010, 04:44 PM   #6
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Re: Keep the bus? Or too many problems?

Thanks everyone for your input!

M1031: Are those computer-controlled? I'll keep an eye on Idaho Motor Pool, they seem totally awesome! As for over-revving, I am worried that having only a 3-speed transmission (last shift is at about 35mph) means I will be over-revving it on hills or even just trying to maintain highway speeds. Are there lots of skoolies out there with only 3-speed transmissions?

Leonidas: While we are planning on making it liveable, we likely won't be doing any intense infrastructure work on it. Just sleeping, cooking, seating, cabinets. No bathroom. It would really be annoying if it totally died and we had to move everything into a new bus, but if we make things modular enough it might not be too bad.

Smitty: Yeah, we couldn't find any diesel mechanics who would come out to the sketchy lot to check out a non-running bus. I figured for $700 split between two people for a non-running bus that wasn't trashed, if we got it running we'd be in good shape, and if we didn't we could probably at least get our money back if we sold it. We've only put another $150 or so into it, and now it runs, so we're pretty happy with that at least. But I think you also touch on the main issue; we know what the problems are, and we don't know what the problems are in any of the $2500-$4000 short buses for sale out there.

Also, is there anyone out there in the Portland, OR area who can recommend a good mechanic for a bus? We want a second opinion since they also told us our transmission wouldn't go into fourth gear so it must be hosed (it's a 3-speed), and overfilled our transmission by a considerable amount because they didn't read the dipstick. They also couldn't tell us what was actually OK on the bus. Brakes, tires? "Well it's not mentioned on this report so I guess they're fine."
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Old 07-06-2010, 05:02 PM   #7
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Re: Keep the bus? Or too many problems?

Quote:
Originally Posted by MonsieurBon
Thanks everyone for your input!

M1031: Are those computer-controlled? I'll keep an eye on Idaho Motor Pool, they seem totally awesome! As for over-revving, I am worried that having only a 3-speed transmission (last shift is at about 35mph) means I will be over-revving it on hills or even just trying to maintain highway speeds. Are there lots of skoolies out there with only 3-speed transmissions?"
Nope. No military CUCVs or HMMVs before 2003 (more or less) are computerized. So your '89 is fine. I have the turbo 400 tranny in my M-series trucks. I keep the trucks running at about 60 mph. I get 25 mpg all day long with that average. I'm sure a bus will be less due to weight and areodynamics. The turbo 3 speed should keep you near 60. I hope this helps.
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Old 07-06-2010, 05:17 PM   #8
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Re: Keep the bus? Or too many problems?

Quote:
Originally Posted by M1031
Nope. No military CUCVs or HMMVs before 2003 (more or less) are computerized. So your '89 is fine. I have the turbo 400 tranny in my M-series trucks. I keep the trucks running at about 60 mph. I get 25 mpg all day long with that average. I'm sure a bus will be less due to weight and areodynamics. The turbo 3 speed should keep you near 60. I hope this helps.
Sweet! Yeah, I got it up to 55 easily. It was LOUD, which makes sense since the engine was about three feet from my ears, but it didn't seem like it was straining at all.
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Old 07-06-2010, 10:52 PM   #9
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Re: Keep the bus? Or too many problems?

Where in Portland are you? East or West? I am on the east side and quite like my mechanic.... I have a 1988 GMC diesel shorty. Leslie
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Old 07-06-2010, 11:48 PM   #10
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Re: Keep the bus? Or too many problems?

Quote:
Originally Posted by Doodlebug
Where in Portland are you? East or West? I am on the east side and quite like my mechanic.... I have a 1988 GMC diesel shorty. Leslie
Northeast. Who is your mechanic? Where are they? Thanks!
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Old 07-07-2010, 03:20 PM   #11
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Re: Keep the bus? Or too many problems?

Here are some pictures for everyone:
http://www.flickr.com/photos/mustard...7624243126758/
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Old 07-07-2010, 07:14 PM   #12
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Re: Keep the bus? Or too many problems?

The trans leak sounds minor...pan gasket is simple enough & that's probably what it is. A bottle of seal conditioner couldn't hurt.

However...what color is the engine smoke, especially at full throttle? My wife has a 6.2 (1986 Blazer), and with no turbo, these engines smoke. Black is fuel (may need the injector pump re-timed...or just a lighter foot on the pedal), blue is oil (worn rings)...but white is steam & may be a from head gasket. If it has ever been boiled over, you might have popped a head gasket. I have no idea if they can be done with the engine in the vehicle, but I'd bet not. Valve cover gaskets look pretty easy, especially the passenger side. Maybe try tightening the cover bolts...that may stop the leak.

Any good shop can do the U-joints...I doubt it would cost more than $100 or so, this isn't a big job for any shop that can work on a bus. The kingpins, however: these are a potential SERIOUS SAFETY HAZARD! Do NOT put this off! A failed kingpin can mean loss of control! This is a pretty big job. Does this bus have independant suspension (control arms & coils, looks like something on a pickup) or a straight axle (big I-beam-looking thing on leaf springs) in front?
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Old 07-08-2010, 10:08 AM   #13
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Re: Keep the bus? Or too many problems?

Quote:
Originally Posted by Jarlaxle
The trans leak sounds minor...pan gasket is simple enough & that's probably what it is. A bottle of seal conditioner couldn't hurt.

However...what color is the engine smoke, especially at full throttle? My wife has a 6.2 (1986 Blazer), and with no turbo, these engines smoke. Black is fuel (may need the injector pump re-timed...or just a lighter foot on the pedal), blue is oil (worn rings)...but white is steam & may be a from head gasket. If it has ever been boiled over, you might have popped a head gasket. I have no idea if they can be done with the engine in the vehicle, but I'd bet not. Valve cover gaskets look pretty easy, especially the passenger side. Maybe try tightening the cover bolts...that may stop the leak.

Any good shop can do the U-joints...I doubt it would cost more than $100 or so, this isn't a big job for any shop that can work on a bus. The kingpins, however: these are a potential SERIOUS SAFETY HAZARD! Do NOT put this off! A failed kingpin can mean loss of control! This is a pretty big job. Does this bus have independant suspension (control arms & coils, looks like something on a pickup) or a straight axle (big I-beam-looking thing on leaf springs) in front?
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Old 07-08-2010, 11:49 AM   #14
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Re: Keep the bus? Or too many problems?

Quote:
Originally Posted by Jarlaxle
The trans leak sounds minor...pan gasket is simple enough & that's probably what it is. A bottle of seal conditioner couldn't hurt.

However...what color is the engine smoke, especially at full throttle? My wife has a 6.2 (1986 Blazer), and with no turbo, these engines smoke. Black is fuel (may need the injector pump re-timed...or just a lighter foot on the pedal), blue is oil (worn rings)...but white is steam & may be a from head gasket. If it has ever been boiled over, you might have popped a head gasket. I have no idea if they can be done with the engine in the vehicle, but I'd bet not. Valve cover gaskets look pretty easy, especially the passenger side. Maybe try tightening the cover bolts...that may stop the leak.

Any good shop can do the U-joints...I doubt it would cost more than $100 or so, this isn't a big job for any shop that can work on a bus. The kingpins, however: these are a potential SERIOUS SAFETY HAZARD! Do NOT put this off! A failed kingpin can mean loss of control! This is a pretty big job. Does this bus have independant suspension (control arms & coils, looks like something on a pickup) or a straight axle (big I-beam-looking thing on leaf springs) in front?
It's the I-beam 5,000lb axle. My jack isn't strong enough to get the front end off the ground, so I can't confirm how wiggly things are. The mechanic wrote "king pins marginal," so I don't know whether that means they're near failure or just more wiggly than they should be. I take it that ANY wiggliness should be addressed ASAP?

We'll do the U-joints ourselves, cuz it seems fun and relatively easy.

As for the smoke color, we're going to assess it again tonight. Every time I've seen the smoke it's appeared sort of greyish-brown. I don't remember it being steamy or sweet-smelling. It's about the same color as what happens if I downshift in my Mercedes 300D which definitely doesn't have a cracked head gasket. It's definitely NOT oil smoke, as I know what that looks like. The smoke is only very barely visible at idle.
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Old 07-09-2010, 11:42 AM   #15
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Re: Keep the bus? Or too many problems?

Sooo... I asked the first mechanic we took it to for a quote on the king pins. They said "oh, we can't give you a book number, but probably $1200 or more." I called around to several other mechanics, including Les Schwab, who all gave EXACT estimates of precisely half that much, for both sides. The folks at Les Schwab said their estimate was the absolute most it would cost, less if the bushings weren't bad.

So we took it to Les Schwab for them to assess how bad the king pins were. I watched them try to torque the wheels exactly as I've seen described for checking the KPs. They brought a couple guys out to try. Their verdict was the KPs are fine, but could use a little grease. And the tie rod ends could use a little grease. They said one of the KPs was a teeeensy bit wiggly, but only barely perceptible, and that we should come back in a year to have them check it again.

So good news!

I'll see if there are zerks on the ball joints. Is that what he meant by tie rod ends?
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Old 07-09-2010, 01:51 PM   #16
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Re: Keep the bus? Or too many problems?

Look at the long steel tube either in front or behind the steer axle. That's the tie rod. On either side the ends of the tie rod hold the tie rod ends. This is a part of how the front end is aligned with toe-in or toe-out.
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Old 07-09-2010, 09:36 PM   #17
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Re: Keep the bus? Or too many problems?

Quote:
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My bus sucked-up over 2 tubes of grease.

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My old M109 sucked up four tubes. One of many reasons as to why I got rid of it.
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Old 07-09-2010, 11:57 PM   #18
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Re: Keep the bus? Or too many problems?

Hi there, I sent you a PM with my mechanics name and phone number..... Leslie
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Old 07-10-2010, 11:32 AM   #19
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Re: Keep the bus? Or too many problems?

Well it turns out when you clean off every fitting and joint under the front end, little zerks appear everywhere! We got them all greased!

Then we turned our attention to doing the U-joint. The [not that great] mechanic told us the middle u-joint was bad. I am doubting that now. I don't hear or feel any driveline vibrations when driving, there is NO play in the joint when trying to turn the shaft in front of and in back of the joint (put the trans in neutral to test), and there is a fresh red grease coming out of the clearly intact cap bearing seals.

The middle u-joint is the only u-joint that is a re-greasable one, so that's probably why it's exuding grease and maybe why they said it was bad? Also, the mechanic couldn't give me an exact quote on the u-joint, just that it would be "several hundred," which sounds high.

So should we bother replacing it if it shows no signs of degradation? Just grease it and keep an eye on it?
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