Originally Posted by Socaliwelder
He says heís replaced the head gasket,oil pan gasket, water pump, oil,coolant, belts and batteries. What does a blowby test consist of? What is B50? Heís asking 3995.00 for the bus. I was thinking more like $3250.00
On the side of the crankcase is a tube. It allows excess pressure to escape. The amount of gas escaping can be measured by attaching a simple meter.
If the rings and bores are showing any significant wear, the amount of gas escaping increases. That is called "Blow By". You will often see buses advertised as "not running, excessive blow-by".
What that means is that the engine is due an overhaul. Many bus engines can be overhauled without removing them from the frame. Engines like the Navistar DT360, 466, 530 and Cummins 8.3 are all examples.
The CATs, T444, 5.9s, etc, need to come out to be rebored.
B50 is the estimate of when 50% of engines will need this work done. For most bus engines that is in the range of 350 to 500 000 miles.
However, school buses that run daily routes are considered "severe-duty", and those numbers come down. At around 12-13000 hours on the meter, most of them are ready for a rebuild.
These are averages and apply to buses as a group, not to any individual bus. Yours might go half a million miles without issue, but on average it is likely to be close to benefiting from work.