Exhaust fumes getting into the cab of older buses?

[RomaniGypsy]

My mother in law (school bus driver for 15 years) said that if she were going to buy a bus to convert, she would specifically aim for one that was 2007 or newer WITH the emissions equipment, because in her experience, running older buses on newer ULSD fuel caused exhaust gases to come into the interior of the bus. She had a major problem with that on her 2006 bus once they switched to ULSD, and she says that many of her co-worker drivers had the same problem.

Any thoughts about this? (It does fly in the face of everyone saying that older buses without emissions equipment are better....)

[EastCoastCB]

Originally Posted by RomaniGypsy

My mother in law (school bus driver for 15 years) said that if she were going to buy a bus to convert, she would specifically aim for one that was 2007 or newer WITH the emissions equipment, because in her experience, running older buses on newer ULSD fuel caused exhaust gases to come into the interior of the bus. She had a major problem with that on her 2006 bus once they switched to ULSD, and she says that many of her co-worker drivers had the same problem.

Any thoughts about this? (It does fly in the face of everyone saying that older buses without emissions equipment are better....)

I'd take her opinion with a grain of salt.
She may drive em, but she aint having to fix em or pay for the maintenance and repairs.
A properly installed exhaust system and a properly sealed up bus won't have you choking on exhaust.

[somewhereinusa]

The type of fuel you use has absolutely no bearing on whether exhaust would get inside. Like CB said if it's exhaust system is in good shape, no fumes inside.

[Skipoffools]

East coast is right exhaust in the cab is caused by an exhaust leak. A proper exhaust system should only leak at the tail pipe.

[Skipoffools]

But I do imagine the older it is the more likely it is to have an exhaust leak. But newer buses also come with new technologies which can prove to be more trouble than a simple leak in the exhaust of some older bus.

[jazty]

Maybe she's correlating the handling of blowby gas with the introduction of ULSD.

Blowby gas is the vapour that gets by the piston rings. As wear increases so will the blowby. It smells a bit different than straight exhaust, probably due to some oil smells in there.

Blowby gas used to be dumped to the environment, usually right at the engine. Now it is directed to the intake to be reburned.

I have a '97 T444e and when working the engine hard up a hill I can smell the blowby in the cab. Otherwise I don't notice it.

[RomaniGypsy]

Originally Posted by jazty

Maybe she's correlating the handling of blowby gas with the introduction of ULSD.

Blowby gas is the vapour that gets by the piston rings. As wear increases so will the blowby. It smells a bit different than straight exhaust, probably due to some oil smells in there.

Blowby gas used to be dumped to the environment, usually right at the engine. Now it is directed to the intake to be reburned.

I have a '97 T444e and when working the engine hard up a hill I can smell the blowby in the cab. Otherwise I don't notice it.

I remember her talking about this and she said that there was some talk about it being blow-by gases. Is there an engine setup (front engine conventional, front engine flat nose, rear engine) that minimizes the chance of this happening?

[cadillackid]

2 things about exhaust gasses..

1. you can extend the blowby tube farther under the bus
2. with an exhaust pipe right out the back bumper of the bus, the most likely culprit for exhaust infiltration is a leaky rear door seal... as that part of the bus believe it or not is pressurized in such a way that will suck gasses in... (remember how they tell you NEVER to drive your jeep or SUV with tjust the back glass open and windows closed? THIS the reason... )..

other thing can be a leaky V-band clamp under the hood and exhaust gets sucked into the doghouse. since the turbo is in there...
-Christopher

[golfersmurf57]

Leak under the hood can be drawn in by the grating for the heater system fan as well

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[RomaniGypsy]

I might have this problem under control. I put in a bid on two buses from a local school district, and despite being pre-EPA regulations, they contain a device called a Spiracle filter which filters and recirculates blow-by gases... so, hopefully this won't be an issue if I win one of those buses.