Guage Questions

[Ben]

I want to put visual marks on my guages that indicate when a problem might be encountered. So, my question is:

1) What PSI would be considered low engine oil pressure (where I'd want to start trouble shooting it).

2) What should be considered to be a high oil temperature?

3) What is a low brake pressure (mine is usually at 120PSI, but I don't know when I should start to be concerned about it)

4) What should be consider a high water temp. Mine usually runs around 195°, but I don't know when I should start to be concerned.

I'm going to put a little red mark on each gauge to indicate when I should start being concerned that way I'll be able to do a quick glance to see if anyting is messed up.

[Jon Wehrenberg]

Ben,

I assume everything is working well, and your idea is strictly to help alert you to a problem. Here is what I would suggest.

On your next trip mark or otherwise record where all the gauges point. It is probable the needles are going to have a range. The coolant temp gauge for example will have a low point, and if you go up a steep hill or it is hot outside it will have a high point.

The same thing applies to oil pressure. At cruise speeds the needle will be in one range, and at idle it will be lower.

The same applies to the air presure gauges and the transmission temperature (oil) gauges, but here is where you need to "read" the gauges, and worry less about the range.

The air presure gauges will cycle normally between two points. What is more important however is not that it is falling out of the range, because by then your problem is severe, but how frequently the needle cycles up and down indicating the compressor is cutting in and out. With no leaks the compressor will cycle infrequently, but if an emergency brake chamber or an air bag (just two of many examples) begin to develop minor leaks the cycling will occur more frequently and that is the time to react.

The transmission oil temperature gauge will have a range when the roads are dry, a lower range when it is raining, but most critical is to never let it exceed around 230 degrees. I don't know if Prevost has a limit (if they do it sure would be nice if they put a mark on the gauge) but oil will break down as the temperature rises and I use 230 as my limit. What happens below that is of no concern to me.

But don't stop there. The voltage should have a mark at the fully charged, key off value, and an engine running voltage depending on your batteries of somewhere around 27.7.

You should note your turbo boost under high RPM full throttle operation. If it cannot reach that under the same conditions that is a sign of an issue that needs to be addressed

This should give you some food for thought. I have no idea how good the gauges are for accuracy, but what is important is noting a change from normal, as opposed to a limit. Most often an impending problem begins to show up as something slightly different from normal, and with any problem an early correction often save some serious Lewbucks.

[Ben]

Yes, Jon, it's just to alert me of any future problems.

Thanks for all the info... I'll keep all of it in mind.

Just though it would be nice to have a visual indication that something might be wrong, so I don't rely too much on my memory.

[Jon Wehrenberg]

Ben the short version is to just pay attention to your gauges. Every pilot here will tell you that after a while they notice a change as small as a needle width and they find out why before it leads into a problem