Hello,

I have a 1989 S1700 International School Bus with a 7.3 IDI with 196,000 miles. My brother was driving it recently when it lost power completely and eventually shut off, with smoke coming from under the hood. Unfortunately I wasn't in the vehicle when this happened. Upon further inspection I believe what happened is the alternator belt snapped (only one was on at the time, should have had two) which put a hole in a coolant hose, and tore off one or two other belts. I came back the next day with a diesel mechanic and we turned the ignition, the starter works fine but the engine will not crank or fire whatsoever, I assume this means not enough compression. There was also very little oil. I am relatively new to diesels and trying to learn more, but I am seeking advice as to whether I should have it rebuilt or replaced, or any other advice would be great.

Thanks,
Spencer

 

These motors can be spendy to rebuild, first I would confirm what you suspect.

If it's shot I would look for a donor first if they are available in your area, some places are awash with rusted out trucks with still fresh motors, some places they're still pulling high dollar and getting put to use, it's highly variable depending on where you are located on how much it's gonna cost.

But first thing look to see what's going on. Overheating usually blows out the head gaskets or throws a rod, can smoke your pistons if run dry long enough, but first I would dig in and determine exactly what it is.

You may have plenty of room to work under a bus hood, I don't know.. But if it's head gaskets and you have plenty of room to work that'd be great. Can do it in frame easy.

First top off the oil obviously, it will turn over right? If it is locked up forget about it and start looking for a motor. If it still turns, you should be able to start it and see what kind of smoke and where it's coming and going.

Unhook and verify glow plugs are disabled. Don't skip this. Check to make sure no fuel lines are damaged, have your brother use a screwdriver to push the schrader valve on the fuel filter housing to ensure good pressure. It should make good squirts - not air or nothing at all.

Got fuel? Motor turns? It's an IDI it should start.. Even If it's smoked it should start.

Shoot 3 short bursts of starting fluid in the breather, and crank. Give little spurts as needed to get it fired. It might smoke or knock, but IDI's die hard.

Now what's it doing? White / black smoke out the tailpipe? Put a rubber glove and secure it with rubber bands on the radiator cap and see if it expands with exhaust gas blowing by from a head gasket / cracked head. Look for brown in the coolant and white in the oil.

Next look for a compression tester the cheap HF can be modified to work, you'd have to search down a thread detailing how to do the mod.

Too bad you weren't driving at the time, this is a thing - if you dump coolant your temp gage won't show hot even though it's burning up, the sensor is dry and see's no hot coolant because it is all over the road. I always keep my eye on the gage for hot - or sudden cool.

If it shows cold when I am driving I'm pulling over immediately. Lately my sensor or temp gauge is acting funny and it's showing cold, or my fan clutch is sticking I don't know - it's only happened twice in the last maybe 3 mos. But it showed cold and I pulled off and checked my radiator - all good just the sensor probably but watch out for it showing cold all the sudden.

Keep us posted and good luck.

 

If it was overheated bad enough to freeze it up you're looking at scored cylinder walls & piston skirts (that why it won't turn over), probably cracked cylinder heads. Chances are it's not savable. Depending on the damage, if the block's ruined there would be a core charge and it can't be overhauled.