I just bought a 1985 f-250 with a aftermaket ATS turbo, and I can only notice boost when the motor is cold. when the motor warms up there is no boost, and I was wondering if anyone had any ideas why this is.


Thanks for you time

 

WOW ....
How do you know you are getting boost? Do you have a guage?
On the ats system there is a rubber o ring where the silver colored cover sits on the intake and there is also a rubber o ring in the neck that connects to that piece. They are the only two place for pressure, unless the manifold gaskets are blown out. To replace those orings, you have to loosen the turbo from the pedestal and lift it high enuf to remove the intake plenum.
Before you do that, make sure the turbo is spinning freely by removing the intake hose and spin the turbine with your fingers (with the engine OFF !!!!!!!!).
It almost sounds like the turbine and the compressor and not connected. Is there lots of black smoke while driving down the road?

 

I think I am geting boost because when taking off cold, I can feel the extra power and it is very noticable. But once the motor warms up I cannot feel it anymore.

 

Steve can you hear the turbo when the rpms get up to 1400 or more? If you do then there must be a problem with something sealing. But boost when cold and none when warm doesn't make sense to me. Do you have a boost guage on your truck?

 

Cool, we must be brother's in arms and fly rods...plus oil burning!!
Regarding the turbo, I'd say the once heated metal has expanded your are getting a leak somewhere before the turbo. Check it out top to bottom...by taking it apart and putting it back together(yeah, a pain in the head). I've found that aluminum is most prone to cause this problem and think the early ATS turbos used that metal for some parts. Might be worth checking.
Also is the turbo seizing once the engine warms up...bearing failure. Take it apart warm to check and see if it spins before going deeper.
Good luck!

 

I may be mistaken but the boost you are feeling when the engine is cold and not feeling when the engine is warm may be the cold timing advance built into the injection pump. Is the engine making a more pronounced "diesel knock" when it is cold compared to when it is warm? If so, the boost you're feeling is probably just the cold advance. Someone correct me if I'm wrong please.
Also, if you want to know if you're making or losing boost, install a boost gauge. Installing a pyrometer is also a good idea.