Truck hot/cold, no power?????

[rd62rdstr]

Okay heres the scenario... my 99 Tahoe was running great, lots of power. Intake gasket went on it. Oil in the water. Water in the intake, air cleaner, etc. I tore it down, decided to go ahead and do the head gaskets as well. Cleaned really well, flushed water system. Changed oil twice. New, cap, rotor, spark plugs and belt. Tried to drive it, motor almost immediately showed hot. Yet radiator felt cool and I opened it, no problem. No boiling over, no steam. Drove it again and it still showed hot, 250*. Stopped and checked again. This time I realized, one half of the radiator (driver's side) felt hot and the other side was cool to the touch. Late night, stores closed, removed thermostat alltogether and the truck ran cold. Too cold, heater wouldnt even get warm. Replaced thermostat with the prescribed 195* thermostat. and the truck ran hot again, 250*. Ran another improper thermostat off an old chevy engine (185*), and its now running about 160*. Noticing good drivability and idle, but loss of power. what could it possibly be? Any ideas?

 

[oldsalt]

Sounds like you got a bad thermostat or 2. --250' ... Wow. That's way out of my comfort zone.
When you say good drivability you mean just around town type of driving but when you jump on it it has no power?

 

[rd62rdstr]

Yep, also thought bad thermostat, took it back got another. Both Failsafe brand. Same thing. Yes around town and I drive on the freeway. Does 65 just fine. But slow off of the line and kinda slow getting up to 65 on the freeway.

---------- Post added at 12:11 AM ---------- Previous post was at 12:08 AM ----------

From what I understand, timing is handled by the computer?? But if it were an older car, I'd say the distributor needs to be advanced a little bit. From what Ive heard, you cant do that on these vehicles. Is that true?

 

[SunlitComet]

A gasket backwards would cause an overheat.

 

[oldsalt]

Good call Sunlit. Hadn't thought of that.
But damn, I think on the 5.7's I believe it doesn't matter which side they are put on. In other words each half of the gaskets have the same cutouts. But don't quote me. It's been a while since I've had one in front of me. Of course intake manifold gaskets are a no brainer as they have the pins that snap in.

"...timing is handled by the computer..."
Yes Sal that is true to a point. After you get things put together with your rotor pointing to the proper position on the dist you still have to dial things in and get your cam retard degrees dialed in. I believe it is +- 3 degrees. Outside of that is too much for the computer to adjust. This is done with a scanner on the car and the rpm's at 1000. After that the computer will compensate as needed.

This still does not address the overheating issue. If you have a thermometer, a meat thermometer will do, put one of those thermostats in a pan of warm water and heat it up and see if it opens. The cooling system is pretty damn simple and my first guess would be bad thermostats. Especially since you said things ran cool without it.

 

[SunlitComet]

Actually another poster just realized he installed his intake gasket backward, head gasket I don't think matters- it is a front/back thing he said unless I read that wrong. Oh the cam retard 0+-2 so any where from -2 to +2 should be fine but if there is no code p1345 it is not an issue.

 

[retorq]

The intake gaskets on the Vortecs should only go in one way if using the plastic o-ringed ones from Felpro. They actually snap into the heads ... I'm in the middle of swapping my top end to a Vortec so I have them out and can post pics of them if you want. The old school intake gaskets CAN matter. If you get the ones with the open coolant passage holes with the the restrictor you put in yourself then it doesn't matter which way they go, provided you leave out that restrictor. Make sense??

 

[oldsalt]

I stand corrected. I did not know that the vortec manifold gaskets were different than the older ones. I have only rebuilt the vortec.

 

[rd62rdstr]

The intake gaskets on the Vortecs should only go in one way if using the plastic o-ringed ones from Felpro. They actually snap into the heads ... I'm in the middle of swapping my top end to a Vortec so I have them out and can post pics of them if you want. The old school intake gaskets CAN matter. If you get the ones with the open coolant passage holes with the the restrictor you put in yourself then it doesn't matter which way they go, provided you leave out that restrictor. Make sense??

Yes, please post. I did use the Felpros and yes they did snap in. Possible they are still backwards??? Sounds like that may be my problem. Will check the timing on the scanner first.

 

[retorq]

http://www.facebook.com/album.php?aid=61760&id=100000140127387&l=176e04453c

You can (should be able to) see the intake gasket close up where it snaps in, there is a shot of the intake side of the head too in there. You can see that it doesn't really matter on the vortecs, there is no "backwards" like the ol school gaskets ...

Old school: