Northstar Engines and System Technical Discussion Discussion, misc questions in Cadillac Engine Discussion; I searched quickly for these answers but didn't see them.
1) I have a 2000 STS with 50k miles. Was ...
I searched quickly for these answers but didn't see them.
1) I have a 2000 STS with 50k miles. Was there a head bolt change to address the head gasket issue? If so when was the change made? Would a 10 F cooler t-stat help with the head gasket problem? I just removed the hood seal to see if this lets extra air flow through to help with engine heat.
2) Underneath the engine cover there is a wire harness that connects to the front injectors and front coil pack and crosses over right over the coupler that connects the plenum and the TB. Mine had some of the plastic shield stripped away and a tag (shiny with black lettering) wrapped around a purple/white wire that said something like vehicle program void if tampering. The wire had black tape wrapped around it with this label on the outside of the black tape. I couldn't tell if something was inside the black tape or if the wire was spliced.
3) Does the engine cover and the coil covers hold too much heat in? The wires under the engine cover seemed less flexible than the wires outside of the engine cover.
4) Is there typically some oil seepage around the crank seal?
As far as the cooling question, the exterior temperature of the engine has nothing to do with the head gasket problem. That is a result of several factors including head gasket seal surface, siamesed cylinders, head gasket composition, bolt length and thread pitch, and aluminum casting porosity faults. I believe the bolt specs were updated to a more aggressive thread pitch in the '00 - '01 series run. Changing the thermostat will also have no effect on head gasket longevity: temperature increases are a result of head gasket failure, not the cause. (Besides, the engine is designed to run at around 212 degrees coolant temperature, so changing thermostats will really mess up the PCM engine control systems due to a "cold coolant" signal.)
As far as the crankshaft (rear?) seal, some are bone dry, some have a bit of leakage, and one in a hundred thousand flat leaks.
Never ran into the warning tag, but it sounds like a warning not to insert aftermarket resistors or black boxes in whatever circuit it is, possibly sending false signals to/from the PCM.
If you've done some homework in these forums you should have gained the knowledge that a Northstar system does not take kindly to attempts at changing its "brains" or trying to gain power where there isn't any. There's some more power in there, to be sure, but it won't come from snake oil or $12.95 bolt-ons.
In my opinion, and alot of mechanics I've talked to, one of the factors for failing hg's is the crappy aluminum gm used for the block. Failures are alot less common on 2000 and up models, but its not unheard of. THe absolute best thing you can do to prevent hg failure is to flush the coolant every 3 years, 30000 miles, sooner if you really want.
And there's no way to get your N* to make more power, its maxed out from the factory.
The thought on the tstat was keeping the engine a little cooler which might reduce the stress on the head bolts / fatique on the aluminum threads - or maybe not.
The wire that has a tag on it just looks like it has some back tape wrapped around it with this label around the black tape. I have to get out my schematics and figure out what the wire does. It doesn't seem like there were any gadgets connected.
If the programing is like every other car I've tuned, there is room for improvement. Whether or not you can get inside the PCM is another issue. For example on a 2002 LS1 corvette, for an ECT from 176 to 221F the timing isn't altered and the A/F during closed loop is 14.63. So a slightly cooler t-stat wouldn't change timing or A/F, but decreases thermodynamic efficiency while providing some potential to reduce knock retard. Skewing the MAF signal at WOT can alter the A/F and tweak timing.