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Seals777 · 02-11-2009, 02:52 AM

We are a band out of South Lake Tahoe, Ca that has a 6v92t in an 81’ Mci-9.

In July ’09 we were experiencing lower power and higher operating temperatures. Normally we operated around 175 on the flats and about 185 on the passes, at the end of this particular tour we were getting up to 185-190 on the flats and 190-200 on the passes. At first we contributed it to the high temperatures of Northern Cal, which can reach 115 in some places, if we did reach 200 we would pull over and let it cool down. We always made sure the oil was good which we used straight 40 and coolant was topped off. The lower power started at the very end so we took it to our mechanic.

The lower power was caused by a broken valve spring and noticed scoring in two of the cylinders. He told use we needed a rebuild and quoted us around $12,000. It ended up being $16,700, which is a lot of money for us. In the rebuild he pretty much did everything including flushing the radiators and he took of the vents off that open and close on the side of the MCI, which he contributed to the initial overheating problem which contributed to the broken spring.

In the last six Months the bus has run great doing a whole tour of the east coast, we have put about 10,000 miles on the rebuild. With the vents off the bus the operating temp has been around 150-165.

This winter we have only been touring the weekends because it makes more economical sense, so the bus has been sitting during the week in temps from 0 -50. It was particularly cold last week when were leaving for a tour of Colorado, so we had to use starter fluid, the bus ended up idling for about an hour do to the sound guy being late.

Leaving South Lake you need to do Spooner pass to get down to Carson. When we got down the pass the driver noticed white smoke out the back and a loss of power. We pulled over say that coolant was leaking and turned the bus off. The driver said that the temp never got past 165 and did not notice a loss of power until the bottom of the pass. On the way down he had the Engine brake on and in second gear.

We called the mechanic and he noticed that one of two coolant clamps had broken at the end of a hose, so we thought that the coolant was coming out of the hose. We put another clamp on and filled what little coolant was lost back up, gal or two, checked the oil to make sure no coolant was in it and went to start it back up.

The engine was seized, and the coolant had been coming out of the top. He was able to un-seize it with a wrench and told us we needed another rebuild quoting, parts around $9,000.

Well this is pretty much a band breaker, without this vehicle which allowed us to skip hotels, carry equipment, move people efficiently and pay our bills, we are dead in water.

So I am looking for reasons for failure and could something have not been done right on the rebuild, which could be covered under some type of warranty. Does it really need $9,000 in parts to fix because he has not opened it up yet? Could using starter fluid cause the liner or o-ring to fail? Is it more likely that the temperature gauge is faulty or could there be localized heating that the temp gauge didn’t pick up? When we opened up the engine is didn’t seem very hot. Why did the engine seize after it was turned off? Is that some type of diffusion welding or does the crystal structure change in the piston making it have a lower density and higher volume?

In the end are we just up the creek?

Sorry about the long post I think it was my way of venting.

Orvil Hazelton · 02-11-2009, 07:30 PM

SEALS: There is little I can do or say to ameliorate your pain except to say that I do indeed hear you. I haven't a clue as to what caused your 92 to seize, except to feel that your original re-builder screwed the pooch somewhere. Good luck. . . where the is a will there is a way. As always, oRV

bdpreece · 02-13-2009, 08:45 AM

Without a tear down it is pretty much impossible to second guess what is wrong. If as the driver says it did not overheat I doubt that the engine actually seized. What probably did happen was something mechanical actually broke and jammed somewhere. Physically turning over the engine may have forced it out of the way i.e. through a valve etc. At this point it does not sound good. I wish you luck. Continue to post here and update us on what is the matter.

Bikeboy57 · 02-15-2009, 03:56 AM

Seals,

You need to post on the Bus Nuts forum.

In short the two stroke Detroits have about ten gazillion "O" rings and seals to keep water, diesel, and oil separate.

One of those failed in the head, allowing coolant into the cylinder. The white smoke you saw was steam coming out of the exhaust. The reason the engine siezed was the cylinder with the leak filled up with water and hydrolocked.

The engine has to come apart again to fix this.

Now whether your mechanic didn't install the seals correctly, or you screwed the pooch with the ether is up for debate.

In my opinion, this one's on you. If the bus ran as many miles as it did without a problem, then it kind of exonerates the mechanic. If he did the job wrong, the issue would have shown up in the first 500 miles.

When the engine was cold, the "O" rings don't seal as well. (Remember the space shuttle failure on launch?) Putting the ether to it caused a fairly violent explosion in the combustion chambers.

Sorry about your problems.

Seals777 · 03-10-2009, 06:46 PM

finally got the right head off and see what we discovered. Need advice if this thing should have been repaired in the first place.

http://www.kodakgallery.com/ShareLan..._photos_button

I was a welding engineer at Ohio state university before dropping out my last year to join this band. At best this looks like what you would get from brazing. No penatration of surrounding metal. At best when machined you would get a nice thin fiction stirred weld. I never practiced and been out of the academia for a while so need real world opinions on procedure.

Thanks

sjholt · 03-18-2009, 04:02 PM

Simple to me. The valve head broke off and punched all those holes in the head. Maybe a valve spring broke first?
It's a time/miles thing. If my diesel ever has to have the head pulled(90k miles), I'm going to replace all the valves and springs and keepers and locks.

Mike Canter · 03-19-2009, 02:40 PM

How many miles on it since the overhaul and how long ago was the overhaul?

I have always been told you never to use starter fluid on a diesel and to only use WD-40 to start them but then I have seen diesels that have an automatic ether primer system for cold weather operations. I think the problem with ether is that you can use too much and several things can happen It can cause massive detonation/explosion which can lift heads, crack pistons and all kinds of stuff. In the old mechanical injection motors when it detonated it would be such an explosion that it would make the motor rotate the opposite direction and run. I have always just used WD-40.

Does the diesel book for your MH have a cold start section. Mine for a Cummins B5.9 states that it is a two man operation to crank the engine then fire the ether in it once it starts turning. It also has a big warning about using too much as it will damage the motor. Did you have the motor cranking with the throttle at mid position when you sprayed in the ether in or did you spray it in then go and crank the motor?