7.3l Diesel Allison Automatic

stevex440s · 12-05-2007, 07:32 PM

I am thinking of buying a 1992 Internation school bus with a 7.3l diesel motor with a Allison transmission for $600. The engine has a overheat problem and the machanic who worked on it said it was losing coolant and the previous own would have to use starter fluid on cold days to start it. He also thinks they ran it hot due to the lack of coolant. The engine runs good but I haven't took it out on the road. Could it be as simple as a blown headgasket, a cracked head, or all the valves are burnt. He did say it was low on compression? Is this bus worth it?

swinada · 12-06-2007, 10:17 AM

why not buy one that has no problems? Replacing that engine will cost you a few thousand dollars. Unless you are a heavy duty mechanic and have the tools and the shop and know how to rebuild that engine I would advice against buying it.

KC10Chief · 12-06-2007, 01:03 PM

Yeah, low compression usually means bad piston rings. Piston rings go bad from being overheated. I would keep looking for another bus. I have a 7.3L in my bus and it's a real dog. If I had it to do over, I'd get a different motor all together even though mine runs great. I've looked into what it would cost to replace my 7.3 if something were to ever happen to it. It's NOT cheap. About $5K. You could buy a really nice bus for that.

stevex440s · 12-06-2007, 11:41 PM

I am really buy this bus to hop up my 1980 s1700 bus with a 345 cid engine with a 5 spd trans. For what it's worth my bus has a 6.5 rear gears. This bus has 5.57 rear with disc brakes unlike my drum brakes. The bus runs really good and doesn't smoke a bit. Also, What is a really good site to upload pics?

KC10Chief · 12-07-2007, 12:15 AM

I use http://www.photobucket.com. You can upload your pics, organize them into albums, and underneath each picture, is a link you can copy so you can paste photos here in the forum, or in E-mails or on a website, or just give somebody a link to the picture. It's simple to use. For the forum, you just copy the [IMG] link. It's the bottom one under the photo.

As for that bus, if you want to use it for parts, it might not be a bad idea for $600. But I really wouldn't mess with that motor if it's overheating and doesn't have good compression.

the_experience03 · 12-07-2007, 12:24 AM

I question just how well it runs. Running hot...using coolant...low compression. It all sounds suspiciously like head gaskets (you'd replace both if you took it apart that far) to me. But how do you know it's not more? If the bores are out of spec you're in big trouble. Even if it is as simple as a headgasket...that's not terribly simple when you're talking about something this size.

It's probably worth the $600, but not for your purposes I don't think.

stevex440s · 12-07-2007, 08:42 PM

Thanks! I'm going to buy it for the rear end. If I can fix the engine reasonably I will.

behappystupi · 12-07-2007, 08:46 PM

EDIT: nvm.

stevex440s · 12-11-2007, 05:35 PM

I went back Saturday to pay for it and I wanted to see if it would start without Starter fluid. I turned the key on and waited for the "wait light" (glow plugs) to go out and turned it over. It was 35C outside. Buy the 3rd try it started! There was no blue smoke at all! I am thinking that it's a headgasket blown, burnt valves, or a cracked head.

phillbus914 · 12-11-2007, 08:29 PM

Word of caution: Never use starting fluid on an engine with glow plugs. The starting fluid could ignite and explode.

Jarlaxle · 12-14-2007, 07:32 PM

Check 2 things here:

1) Thermostat. This is a noted trouble spot for the 7.3 diesel. There are a bunch of bad ones out there. Try replacing it, it might be the problem. Note: these engines run 200-210 degrees. This is normal & harmless.

2) Glow plug system. You might only be getting the light. This is another known trouble spot. Lots of people have bypassed the relay system & wired them to a manual switch. Beware, these are 6V plugs and are easy to burn out if left on too long (keep it under 30 seconds at a time).

You might well have a perfectly good engine.

lapeer20m · 12-15-2007, 09:55 AM

Quote:

Originally Posted by phillbus914

Word of caution: Never use starting fluid on an engine with glow plugs. The starting fluid could ignite and explode.

x2!!!

there have been stories of intake manifolds getting blown right off of the engine because of starting fluid ignited by glowplugs.

KC10Chief · 12-16-2007, 01:38 AM

My 7.3 runs pretty warm. Around 190 to 200 degrees is normal it seems. If I'm really getting on it on the highway, it will get to around 210.

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