Engine/Transmission (1998.5 - 2002) Manifold and turbo heat discoloration

[Ncostello]

When looking at some used truck (I'm wanting a 4x4)... I often notice that the manifolds can be completely rusted and the intake side of the turbos are sometimes discolored. By that I mean what should be silver paint often looks like its got a yellowish tint to it. My 99's manifold is only rusted a little at the turbo flange while the rest of it appears iron grey still. And my turbo (cool side) is still nice clean silver.



Did they use clear coat on some turbos which turns yellow or ???. Or are these engines ran so hard and hot that the heat burns everything clean off the manifold and causes the fan side of the turbo to over heat the housing and bake the paint into a yellowish state?



Guess I'm trying to base an engines past life on looks of these items which are subjected to potential high heat. I've seen too many nice looking engines with high miles that still look almost showroom new to view this discolor condition as normal.

 

[darkhorse]

I did read somewhere on here that the yellowing of the compressor housing is due to heat from over boosting. Mine still looks like natural aluminum at 42,000 miles. The exhaust manifold still looks like black VHT paint too.

 

[TboneMan]

I did read somewhere on here that the yellowing of the compressor housing is due to heat from over boosting. Mine still looks like natural aluminum at 42,000 miles. The exhaust manifold still looks like black VHT paint too.

My turbo has this yellowing and I am stock (105000 miles). I have seen 1200F EGT's (pre-turbo) a couple of times while towing but only for a minute or two at the most.

 

[RustyJC]

Based on what I've seen, if it pulls heavy 5th wheels, the compressor discharge housing will most likely be amber. Yes, the turbo (the engine, in fact), has a clear coat that will discolor when subjected to heat. No big deal.



Rusty

 

[Boondocker]

yellow turbo

My experience bears out what Rusty said. A year ago, at 25K mi. , my turbo looked silvery stock. Now, at 40K mi, my turbo color has yellowed. The engine is the same configuration, the driving style is the same (conservative). The only significant difference, other than total mileage, is that I bought a 9600 lb. 5th wheel trailer a year ago and have towed it around 3000 miles.



Based on observation, since I have no telemetry:

Unloaded -

ave. boost: 5-6 lbs

ave. EGT: 500-600



Loaded -

ave. boost: 10-12 lbs

ave. EGT: 800-900



There have been a few grades, for a few minitues at a time, that push up the loaded averages. My turbo is a stock HX-35 and my gauge only goes to 30 psi, so pegging the boost gauge is a no-no. My EGT gauge has a yellow zone starting at about 1000 degrees. I don't like the needle in the yellow either.



The bottom line is that my turbo is yellowing without any abuse.



Neil

 

[rashwor]

Rusty is a more experienced tower than I, but I often pull 14,000+# and have no discoloring on the turbo. I do have rust on the exhaust side of the turbo and manifold.



I do driver conservative when towing as my EGT has never hit 1200* pre-turbo (close at 1120*) and I run the EZ on setting 3 all the time.



IMO... I personally would be a little concerned as I have seen ones that I know were run very not and they were very discolored. If they will discolor without running that hard, well then it sounds like luck of the draw and a roll of the dice.