High Exhaust Temp

[roscoe]

Hello guys, well no work today so jumped in my pickup buzzed into Mack and picked up a thermo coupler for the turbo.After some talk with the mechanics

we have agreed that the boost is correct at around 30-31 lbs. We also discussed the possability of an electronics glitch but i'm not getting any

malfunction light and we have scanned the system with there laptop and found nothing.Before all of this started the exhaust temp would rarely get

to 900 degrees. Water temp is still 180-190, The bearing in the turbo was letting the impeller drag in the housing so we replaced the turbo

still high exhaust temp so we checked the charge air cooler it was cracked down the hot side so that was replaced, still high exhaust temp

air and fuel filters changed, still 1150 degrees and climbing. That is now where i'm at so now i will replace the thermo coupler. If that

fails we are going to hook up Macks lap top and see what temps it will read compared to what the gauges say.

[fjh]

Thanks fjh I didn't snap onto what MackPro is saying til you said that. Does the high boost pressure mean I need a new boost relief valve? It seems to have plenty of power and the fuel mileage is good. Maybe my gage is wrong?

Woe is me. I'm a worrier so I better check this out.

Nope Jerry yours is on the money if you push it on a cold day you can hit 38 with a 460.that turbo will put out far more air than your engine can use but with out more fuel more air is useless!I have personaly pluged the by pass valve ,It will bang the boost gauge off the end of the gauge.ya don't want to go there.

The waste gated turbo is designed to put no more than 33 psi into that year, FOR WHAT ever reason, These engineer types put a derate in there at 33 psi, As if more air would hurt the engine

WHAT EVER!

[JerryB]

Nope Jerry yours is on the money if you push it on a cold day you can hit 38 with a 460.that turbo will put out far more air than your engine can use but with out more fuel more air is useless!I have personaly pluged the by pass valve ,It will bang the boost gauge off the end of the gauge.ya don't want to go there.

The waste gated turbo is designed to put no more than 33 psi into that year, FOR WHAT ever reason, These engineer types put a derate in there at 33 psi, As if more air would hurt the engine

WHAT EVER!

Okay thanks I was worried about it. I like to keep everything as well maintained as possible.

I love my old mess again after you guys talked me through the coolant headaches. I've been running around 3500 miles per week with only the fan hub going out since the coolant debacle. I wish it had a grease zert instead of the prepacked bearings.

[roscoe]

33 lbs is the max the the computer will allow,i blocked the waste gate acuator off and ran it up a hill it hit

about 33 or so and then cut the power way back.The electronic malfunction light came on and an over-boost

code blinked out. Don't you just love computers.Now if they could just tell why the high exhaust temp is

happening they might do some good.

[roscoe]

The saga continues, replaced the thermo coupler on the exhaust pipe today. Tried to get it heated up but running around without

a load just doesn't let it pull hard enough to develope much heat. Tuesday will be the test.