repower question

turf · 08-10-2021, 05:49 PM

how would you do it?

love my bus. its got a lot of miles.... coming up on 400k.

someday its going to need a repower and i'd like to be ready for it.

93 bluebird

cummins 5.9 12 valve

AT1545 trans

how would you do it?

run it until it breaks then be at the mercy of the shop you get towed too?

have a back up motor or motor/trans ready to go?

wait til it breaks and have it rebuilt?

rebuild it preventatively?

reman?

what do the experts think?
what's cost efficient?

BarnYardCamp · 08-10-2021, 06:52 PM

maybe start shopping around for a used engine from something wrecked? I'd want to see it before the scrap yard pulls it from the donor vehicle...maybe scratch in a secret mark some where not too obvious so you know they didn't pull a switch on you....maybe engine/trans combo since the tranny has all those miles too.

Ronnie · 08-10-2021, 09:00 PM

If you wait till it breaks then you are likely stuck somewhere with little options. I would get another engine to rebuild and trans as well. Build what you want and then change it out before a total failure.

cadillackid · 08-10-2021, 09:40 PM

Most times an engine gives you warning. If you have the ability to build a repower setup ahead of time then I’d probably do it and swap it in.

Sure an engine can break.. the rings can break a valve can drop , etc but most 5.9a give warning signals.. lots of blowby , lowering oil pressure , cam train gets noisier than usual, more smoke than normal at startup etc .. things telling you “I’m tired help me”.

Mekanic · 08-10-2021, 10:15 PM

Quote:

Originally Posted by BarnYardCamp

maybe start shopping around for a used engine from something wrecked? I'd want to see it before the scrap yard pulls it from the donor vehicle...maybe scratch in a secret mark some where not too obvious so you know they didn't pull a switch on you....maybe engine/trans combo since the tranny has all those miles too.

I'd want to hear it run. you can tell a lot for the sound a diesel makes.

AND
have a back up motor or motor/trans ready to go? Yes

have rebuilt then plan for a swap ? Yes

magnakansas · 08-10-2021, 10:50 PM

My bus came with out a drive line. I had built for me a hopped up 12 valve... about. 350 hp- 700ft lbs torque everything new or rebuilt. I chose a 6 speed manual transmission. Nv5600. All refurbished before the bus rolls.

I would buy good used 12v with Bosch p7100 fuel injection and rebuild, Allison 1000 if it will take the power input or 2000 series.

Another way......I saw a motor home with 5.9 and Allison for. $2500 near me, Motorhome part crap. Less than 100,000 miles on the driveline

William

turf · 08-11-2021, 06:38 AM

cool, thanks, i appreciate all the answers. keep em coming.

i've always heard that the 5.9 was a disposable engine.

i've re-powered 3 vehicles - 2 were rebuild , 1 is a swap.

i dont think i'd pay for another rebuilt engine. imo - no one does it like the factory. i haven't had a good history with , did a vw a long time ago and it was ok, a ford that only lasted another 500 hours or so. i did a swap on a toyota that never missed a beat.

so when y'all start saying a rebuild.... well.....where do you get a new 5.9?

i think the block in there now will be so far out of spec, i have no interest in having my block rebuilt.

am i looking for any 5.9? does it need to be my cpl#? does it need to be out of a schoolbus/medium duty truck?

is there a new engine option?

thanks

Booyah45828 · 08-11-2021, 09:53 AM

I've got a spare engine and trans on the shop floor. I bought them a few years ago with the intentions of rebuilding them, and then swapping them into the bus when I had the free time. The bus runs great yet, and needless to say, my free time has been nearly non-existent, so none of it's happened.

The spares I went with are a 7.3 idi and an mt643, similar to the 6.9 idi/at545 already installed. I've thought about upgrading to a powerplant/transmission out of a semi. But to do that, I'll likely have to upgrade to a heavier front axle, which would most likely mean a switch from dayton to budd rims. I'd would then have to change the rear axle to budds as well, so I might as well install a different one with a better ratio in it. And if I'm upgrading the axles, I might as well install ones with air ride.

The whole upgrade idea seems to spiral out of control when I do it in my head, so it will likely never happen. Honestly, the spare swap will likely never happen, unless the current ones let go and I'm forced to. And in that case, what's the value of doing all of that work to a 35+ year old bus equipped with a basic conversion?

Booyah45828 · 08-11-2021, 10:04 AM

They call the 5.9 a disposable engine for a few reasons.

#1 is that any parent bore engine rebuild requires engine removal. So when trouble arises, the engine is always removed.

#2 is that the 5.9 engine is pretty common and has been used for decades, so most would rather swap in a used unit and be back on the road vs waiting a month+ to reinstall the original engine.

I'm not sure what I'd do in your scenario. I think the core 5.9 block is compatible with what you have from the 80's until they went common rail in 2003. Or you could upgrade to an electronic version engine, but you'd be losing the reliability of the mechanical injection system. I don't think I'd upgrade to a different make or engine as fitment issues would be a challenge.

And then we come to the at1545. I'll apologize, as I think I was one of the supporters of you going with it in the beginning, but it really is a rare transmission, and you'll likely be better suited with a more common option.

Mr4btTahoe · 08-11-2021, 10:05 AM

You've got all kinds of options.

If you want to stick with the 5.9 Cummins.. I'd pick up a used engine and have it freshened up by a reputable builder or do it yourself. These engines are well known and plentiful. While you are at it, go on and have the injection pump and injectors rebuilt. Have it all ready to go and when you get some down time, swap it in.

400k isn't too bad really though as long as it's been maintained. If blow by starts picking up or oil consumption, leaks, etc.. then you know it's time.

The fuel system is the biggie. A failing pump or stuck injector can melt one down pretty quickly.. so be sure to have the pump and injectors rebuilt at the same time by a bosch certified injection shop. At the same time, you can have them bump the power up a bit if you want. Wont cost extra as it's already on the bench. An extra 15% or so would be noticeable yet safe.

The trans.. well you've got options there too. If you have a 545, I'd suggest upgrading while doing the work. Its already apart... might as well make it better.

A MT643 is a pretty straight forward swap.. or you can go with one of the electronic transmissions with overdrive like the 2000 series or the MD3060.

Just depends on what you want to do. If you can do the work... you have a LOT of options.

Ronnie · 08-11-2021, 12:02 PM

Quote:

Originally Posted by turf

cool, thanks, i appreciate all the answers. keep em coming.

i've always heard that the 5.9 was a disposable engine.

i've re-powered 3 vehicles - 2 were rebuild , 1 is a swap.

i dont think i'd pay for another rebuilt engine. imo - no one does it like the factory. i haven't had a good history with , did a vw a long time ago and it was ok, a ford that only lasted another 500 hours or so. i did a swap on a toyota that never missed a beat.

so when y'all start saying a rebuild.... well.....where do you get a new 5.9?

i think the block in there now will be so far out of spec, i have no interest in having my block rebuilt.

am i looking for any 5.9? does it need to be my cpl#? does it need to be out of a schoolbus/medium duty truck?

is there a new engine option?

thanks

Well what is a rebuild anyway? throw some new pistons and rings in and call it a rebuild some people do call that a rebuild.

So In this case yes taking it to a machine shop and have the block machined as needed. All parts inspected, and checked for proper fit, replace as needed. A good thorough rebuild done by a machine shop should last as long as the original build.

I do not like putting in a used engine and hoping for the best. If you go with a used engine at least do a compression test, and check oil pressure fully warm at idle. Worn bearings will show low pressure at idle when hot. Put a scope into the cylinders and look for the cross hatching that should be there on the cylinder walls. Do this while the injectors are out for the compression test. No cross hatching visible, then time to tear it down and do a full inspection and build accordingly.

turf · 08-11-2021, 01:02 PM

the ford was like that.
i paid a machine shop a lot of money to return the block to factory spec. supposed to be good as new or better.
it wasn't long before the crank wore out the machine shop welds and the pistons were slapping the cylinder head.
sold the car to a neighbor when i first heard the slap. the neighbor junked it 2-3 years later.

the vw lasted a long time, another 100k+, and i'm still driving the toyota - swapped at 210 - now 250k with an 80k motor from copart.

"rebuild" scares me

Mr4btTahoe · 08-11-2021, 01:21 PM

Quote:

Originally Posted by turf

the ford was like that.
i paid a machine shop a lot of money to return the block to factory spec. supposed to be good as new or better.
it wasn't long before the crank wore out the machine shop welds and the pistons were slapping the cylinder head.
sold the car to a neighbor when i first heard the slap. the neighbor junked it 2-3 years later.

the vw lasted a long time, another 100k+, and i'm still driving the toyota - swapped at 210 - now 250k with an 80k motor from copart.

"rebuild" scares me

Sounds like a machine shop that doesn't know what they are doing to me. There are a LOT of those out there. You need to find a shop that specializes in the engine.. or swap to a DT and do the in-frame yourself. Slap in new cylinders, pistons, bearings, rings, seals.. for ~$1200 in parts from IH. Good to go. Freshen up the fuel system and have another 500k miles of worry free travels as long as you keep up on maintenance.

Personally, I would much rather have an engine that could be in-framed (wet liner) such as a DT.

Booyah45828 · 08-11-2021, 01:31 PM

Eh, I'm on the fence on that.

Having the ability to in-frame is nice, but on something that will never see 500k miles, I'd rather have a parent bore engine.

Of all the problems the 6bt/isb has had, I've honestly had to replace or rebuild very few. Where as I've done several inframes on dt's that had no issues aside from liner o-ring failure. Without those o-rings failing, I feel the mechanical dt would be 2nd to none in the reliability department. So, you can view the ability to in-frame as an asset, I view it as the Achilles heel.

Ronnie · 08-11-2021, 04:47 PM

Must say I like the 6BT myself and have had several. All of them have served me very well. Just would not fit in the short nose of our bus, otherwise would have put one in it.

Rock-N-Ruth · 08-18-2021, 04:13 PM

Quote:

Originally Posted by turf

how would you do it?

love my bus. its got a lot of miles.... coming up on 400k.

someday its going to need a repower and i'd like to be ready for it.

93 bluebird

cummins 5.9 12 valve

AT1545 trans

how would you do it?

run it until it breaks then be at the mercy of the shop you get towed too?

have a back up motor or motor/trans ready to go?

wait til it breaks and have it rebuilt?

rebuild it preventatively?

reman?

what do the experts think?
what's cost efficient?

The Rock-n-Ruth method was to buy a second bus in full running condition just in case. We got our first bus from the Gilbert School System in Phoenix, AZ for $1800. We started talking about what it might cost for tranny repairs after we sprung a leak and had a close call. We figure a tow from the middle of nowhere might cost a grand. Repairs could run several thousand. Best to have a backup plan.
The new bus also from Gilbert, is a few years younger, same powerplant, md3060 tranny, and cost us $1500.
We are thinking about buying a bus every year if we can keep getting these deals. Ya never know, we might end up with a fleet of skoolies.
If money was no object, we'd probably rebuild the engine and transmission in the parts bus and do the swap around 500,000 miles. But as it goes we will probably start a build in the newer bus and retire tis bus as the parts bus when the new build is done.

magnakansas · 08-18-2021, 06:19 PM

I think cummins is now building new 5.9.... I have seen a print ad for brand new cummins 5.9 from cummins I dont know what version.

I have always built my own engines, but every cylinder head comes apart and is checked and measured when it comes back from the shop..... Every last nut and bolt is my responsibility only.

I agree, the factory does it best..... except in some very rare cases.

william

LargeMargeInBaja · 08-18-2021, 11:53 PM

We owned a 1991.5 Dodge Cummins 4x4.
We towed boats and loaders on flatbeds.
We carried a ten-foot camper.
We trudged up rough logger tracks towing three ton of oak in a 4,000# trailer.
We put around 550,000 miles on that 359ci.
.
After 27 years, a friend desperately needed it.
As far as I know, it is still going strong.
.
Disclaimer:
We acknowledge two people can have different experiences.

turf · 08-22-2021, 01:02 AM

i did not get a history of my bus when i got it.

its a bookmobile, retired at 300,002 miles.
thats when i got it.

i was working on the motor today and notice a tag i had not seen before.

the p-pump has a tag on it that says "Cummins recon remanufactured in Mexico"

not sure if that applies only to the pump or the whole motor.

maybe this thing isn't as old as i thought it was.

Ronnie · 08-22-2021, 05:38 AM

You know it might be time to really assess what the condition of the engine really is. Do a compression test. Does it smoke when started, how much oil does it use ? With an accurate gauge check oil pressure fully warmed up after driving for a while, do this at idle. Refer to factory specs for the proper range it should be. All these will give you a real indication of engine condition. Then you can decide what if anything needs to be done.

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