I changed the Opti, plugs, wires, water pump, thermostat (put in a 160), and thermo sensor. The SES light came on and she overheated. The heater also failed to blow hot air. After reading posts on the board about 160 stats, I put the 180 back in and put the old thermo sensor back in. I bled the coolant and still, the SES is on, she overheats even when sitting at idle, and the heater fails to blow cold air. I felt the lower to hoses coming from the water pump and they're cold...even though the gage shows the engine is over heating. I'm lost. Is it possible I put the water pump in wrong or the pump itself doesn't work? For some reason hot water isn't running throughout the engine. As for the SES, I'm also lost there. I went to autozone and had them run the scanner on the car, it shows NO codes. The car is a 94 Z28 totally stock with 110K miles. Thanks

 

If the SES is on, the PCM is throwing a code. Alot of people have had problems with Autozone not knowing what they are doing. Take it to a dealer, and see what they say.

If you're blowing cold air through the heater, your heater core may be clogged up. Time to flush that bad boy. Did you also properly bleed the cooling system? Are your cooling fans coming on?

 

Yes, both fans are coming on. In fact, they stay on now. As for the code, shouldn't something at least flash when running a scan? I don't even get a flash. As for bleeding the system, I'm assuming that I'm doing it right. I filled through the Thermostat housing first. I then opened the bleed screws and filled the radiator. I closed the bleed screws once a steady stream came through. I left the cap off and started the engine. It burped a few bubbles and eventually just flowed out. While the car car idled it actually raised the gage into the red (seemed odd). The top hose was warm but the bottom two weren't. Heck, I didn't think a car could overheat just sitting their ideling for 5 minutes.

 

When you scan for the code, the dash SES shouldn't flash; it should just stay static.

Is your thermostat stuck closed?

Are you losing any coolant? It's also possible that your water pump is shot.

 

As I said, I placed a new 160 stat in and it overheated losing coolant out of the overflow tank. I then put the old 180 back in and it too overheated. The water pump is a brand new (not rebuilt) pump. Is it possible that I might now have installed it correctly? Though it's hard for me to believe...seemed so easy...I may have failed to get the coupler on correctly or something.

As for the SES, that's news to me. I thought the SES light flashed the code on those older GMs....hmmmm

 

you didn't forget the waterpump shaft sleve thing did you? the thing that connects the waterpump shaft to the little shaft comming out the timing chain cover?

 

Did you remember to add the water pump driveshaft coupler?

EDIT: Beat me to it!

 

You can find out your code since you have a 94 OBD I with 12 PIN connector...just take a jumperwire (or paperclip) and stick it in the last 2 terminals of the top row. Do this then turn thekey ON but DO NOT start the car up... It should make the SES light blink the number 12 ( One blink, short pause, 2 blinks = 12) I think it does it 3 times showing that it is in diagnostic mode, then it will move on to the troublecodes blinking them out in the same fashion 3 times followed by a longer pause then the next code, once all codes have been shown it will blink the code 12 again I believe...start with that, write down the codes it shows you post up the numbers and I can tell you what the codes mean....


--Tim

 

You cannot use the paperclip trick on 94s. It's been rumored that some VERY early 94s can do it, but it has not been proven. You need to have it scanned with an OBDI tool or scanning software.

 

Just suggesting since he already took it to AZ and they coudln't find anything...(I'm not too happy with AZ right now myself. )



--Tim

 

I invested in an AKM cable and a cheap laptop and free scanning software to scan it myself, so I wouldn't have to put up with it. Best $300 I ever spent!

 

No, I didn't forget the coupler. I think I'll just pull the damn thing off again and see if there's anything to see. This is whacked. Thanks for the help folks

 

Take out the radiatior, take it to a radiator shop to have them them rod it out. Also, it will probably be a good time to replace the plastic caps. Good Insurance.


Make sure, your lines are not clogged.

 

are you sure you plugged in all the electrical connectors?? I know I forgot to the other day when I changed my waterpump. It made both my fans stay on and my SES light. It was the one that plugged into the bottom of the waterpump. HTH
-Ryan

 

tripple check all your coolant lines are going to the correct places on the waterpump.

if thats fine, take off the top of the waterpump and remove the thermostat. is it full of water? if no, then fill it through the t-stat spot.

if thats full already, then put it all back together but leave the t-stat out... run it once and see if it overheats again. if it doesn't then get a new t-stat and your problem is fixed. also, MAKE SURE your not installing the t-stat upside down, and that you have a t-stat designed for the LT1 engine (Reverse flow).

if it overheats again, then i'd try a different waterpump, maybe the one you have is hosed.

those are the steps i'd take... also couldn't hurt to get the SES code if its not going to overheat your car getting to someone that can do such things