8V71 Mechanic leaves more questions than answers

viento1 · July 28, 2009, 12:43:20 PM

The coach supposedly had 200 000 km on the motor before the previous owner hit something and drained all the oil out.
The coach now has 50 000 km on the new rebuild - supposedly

Original Complaint:
Poor mileage,
poor power,
excessive slobbering from exhaust manifold connections (I dont idle by the way)

Results of 5 hour inspection...
Rubber from air filter to Blower has a big hole in it - allowing dirt and debris to enter the engine.
2 cylindars no longer have cross hatching, they are now polished causing blow by. he did not have a fiberoptic scope

I requested a compression test to confirm cylinder problem he said too labor intensive.
I suggested maybe with so much dirt the blower may be ruined but he did not think that would be a problem.

He is preparing a quote... what he does not know is that he already blew my repair budget for the year!

Thoughts

gumpy · July 28, 2009, 01:11:08 PM

Well, if the rubber between the filter and intake did have a big hole in it, it certainly could have sucked in a lot of dirt, and could very well have caused the problem.

I don't understand why he won't run a compression test, though. I guess if my mechanic is telling me the cylinders are blowing by, I'd like to have it backed up with compression
numbers.

I think I'd definitely get another opinion from another qualified 2 stroke mechanic. Where are you located? Maybe someone here can recommend a mechanic close to you.

craig

luvrbus · July 28, 2009, 01:27:40 PM

I am not defending the guy but he told you the truth about a compression check it will take about 8 to 10 hrs not a easy task on a DD 2 stroke engine.
Also he does not need a scope to inspect the pistons and compression rings on a DD 2 stroke you can look for yourself by removing the air box covers on the engine.
With the hole in the intake hose bet he is not far off sounds likes overhaul time. good luck but this one doesn't sound good

viento1 · July 28, 2009, 01:32:06 PM

Thank you,

I am still in shock and prefer to think it is really nothing...

NJT 5573 · July 28, 2009, 01:49:47 PM

Its a 71, do you have to have a perfect one? The bearings are still good and its not missing so drive it. Maybe it needs a new air filter! 71's run along time with problems, it don't sound like you have broken pistons or dropped valves, so just run it until it gets so bad it won't go over the hill. By then you can build/buy a nice 8V71 T and then you will smile.

I doubt it is any less dependable with the wear issues, just keep it full of oil and wound up! It never had much power to begin with and I doubt you will notice much power difference if you repair unless you have a bad injector or something along that line causing the wet manifold. Cold start it and put your hand on each exhaust port at the manifold and see if they are heating evenly from firing. If they are, drive it.

buswarrior · July 28, 2009, 02:37:19 PM

Yup, if it just has two cylinders that need fresh liners and pistons, pay the nice man for his diagnosis, leave all bridges intact behind you, DRIVE IT out of there and carry on.

Short change the oil for the dirt.

Lots of busnuts can help you change out a couple of cylinder liners, just for fun, or for a modest sum.
Parts are relatively cheap, the shop rate will kill you.

Which busnut clubs do you belong to?

Do you have a BBQ and a cold refrigerator?

happy coaching!
buswarrior

luvrbus · July 28, 2009, 02:46:14 PM

The guy probably just pulled 2 air covers 1 on each side and saw enough. Dirt in engine all 8 are going to be bad ask Sean

good luck

gumpy · July 28, 2009, 02:56:54 PM

Quote from: luvrbus on July 28, 2009, 01:27:40 PM
I am not defending the guy but he told you the truth about a compression check it will take about 8 to 10 hrs not a easy task on a DD 2 stroke engine.
Also he does not need a scope to inspect the pistons and compression rings on a DD 2 stroke you can look for yourself by removing the air box covers on the engine.
With the hole in the intake hose bet he is not far off sounds likes overhaul time. good luck but this one doesn't sound good

Well, I'm learning something new here. I did not realize you can pull the air box covers and inspect the piston and compression rings.

viento1 · July 28, 2009, 04:17:17 PM

I just got back from the Shop. They ended up being pretty down to earth (once I actually spoke with the mechanic) the front end guy had me a quote of 11k to start. The mechanic said the same thing as you guys. Get out there and drive the crap out of it, have some fun and try and finish it off.

Not everything adds up to me. I got to look inside the airbox and injectors and jake brake assembly - its not that complicated that is for sure. I think I will pull the motor out of my other bus as it is a strong running motor. powerful, great mileage, starts in the cold no prolem...

Having said that, my old motor smokes until warmed up then it clears up and runs beautifully clean no smoke no nothing - clean clean clean.

buswarrior · July 28, 2009, 04:44:03 PM

Every single thing you saw under those valve covers that has threads on it has to be set to exacting measurements.

A long and tedious job, requiring your attention and fortitude to not miss any of them, and the engine to be cranked by hand to the correct position for each set.

And a number of specialized tools, which Dallas will tell you shortly their worth.

Yes, straight forward, but steps easily missed as the hours go by.

happy coaching!
buswarrior

larryh · July 28, 2009, 05:39:17 PM

Your mechanic did you a real service by telling you it was time wxtensive to do a compression test when you tear it down to repair the work would be done again to repair the motor and 10 hrs @ 125.00 shop time would equal 1250.00 and nothing but a compression check and that would more than cover the charge for two liners and pistons.

For you go to a harbor freight and purchase a infrared meter and start engine and check each exhaust port on manifold and write down with soapstone on manifold each cylinder temp then add a gallon of lucas oil treatment to crankcase and take out and run for 50 miles or so then come back and take each cylinger temp again and see what you got.

Bet you will be good to go with a slightly used engine and good for another 100K or better. Enjoy what you have.

Larry H

viento1 · August 10, 2009, 10:45:53 PM

I got my bus back and they charged me 11 hours - $1600.00!!!! I requested the shop notes and they can only account for 7 hours. Ok, so from 5 hour quote to a 7 hour bill... not bad. BUT to run up to 11 hours

? I think that is just them trying to cover overhead for the week! It would not be so bad if they actually ran the rack or did that compression test.

I added some oil treatment and ran the crap out of it for half a tank. All that happened is I used up fuel faster

Anyone going to burning man? Anyone close to Alberta? Anyone with a guide for replacing cylinder kits?

I just cant get my head wrapped around this problem. 1) if the cylinders are a problem, why am I not burning any blue smoke?

kyle4501 · August 11, 2009, 05:20:17 AM

My guess -
Due to the blower, the cylinders are never under a vacuum to pull the oil past the rings like a 4 stroke, so there isn't much oil getting past the rings.

Also, if the compression isn't enough to burn the fuel, it won't burn the oil, just spray it out the exhaust.

poppi · August 11, 2009, 07:15:30 AM

viento1
"Anyone close to Alberta?" Montana is kind of close

So are you still going to swap engines?

Good luck on either way you decide.
Skip

bobofthenorth · August 11, 2009, 07:38:13 AM

Quote from: viento1 on August 10, 2009, 10:45:53 PM
Anyone close to Alberta?

Where in Alberta? Its a big province. We'll be in Medicine Hat this week and Airdrie around the end of August.