Ok, so its finally back together with new cam, lifters, rockers, timing set, head gaskets (polish and port).. But it is overheating.. Did an initial start and run, sounds really quiet now without all that lifter noise.. Pretty smooth for just setting timing by guessing on the position after putting the dizzy back in..

Looking at four possibilities for the overheat; 1) timing is not set to final yet, 2) thermostat is stuck, 3) air trapped in heads and block so thermostat isn't getting wet and up to temp to open, 4) wrong gasket somewhere.. I double checked the head gasket part numbers and all the holes seemed to line up ok although the water holes are much smaller than the holes in the heads and block.. Seems like the holes in the gasket were smaller in the old gasket too.. The water pump gasket matched fine.. Did not replace the thermostat since it is relatively new but probably should have anyway..

Watching the heat gauge, it moves up steadily without that pause caused by the thermostat opening followed but another slow rise until the fan kicks on.. My radiator fan did not kick on either even though the temp gauge went above the trip point.. Can't remember if the fan is controlled by the same sensor as the temp gauge.. If so, I may have two problems going on here..

Going to set the timing tonight (although it is idling a bit fast) and I guess pull the thermostat (a pain now that the intake plenum is on).. Anybody experienced something similar or think that air trapped in the heads and block is a likely scenario for the overheat???????????

By the way, the new wider timing gear and chain (correct one for Camaro) did fit in the timing cover.. Heard a noise on first start up and thought the chain was rubbing the cover but I think it was the alternator bearing.. It went away quickly..

 

That all sounds like an air pocket in the coolant.

Do you get heat if you turn the heater on?

 

That's what I am hoping it is... It was late last night so didn't try the heater thing... Any ideas how to clear an air pocket without pulling the thermostat and pouring coolant in from the top??

 

I usually drill a small hole in the thermostat. Just a 3/32" or so, enough to let the air bleed out past it.

Not having the timing correct (too retarded) will cause overheating.

The fan is ECM controlled from the CTS sensor. To force it on easiest it to disconnect the A/C high pressure switch connector.

RBob.

 

Looks like a pull the theromstat job tonight.. May as well put in a new one and drill it for future reference.. Maybe that was why I couldn't get much coolant out when I tried to flush it before, essentially a vacuum lock wouldn't drain the block through the lower hose.. Drilling the hole may make it easier to flush in the future..

 

Ive started drilling 1/8 holes in mine for this reason. Also, make sure your heater is turned on when you install the coolent. That way it will kick the valve over so you know your getting fluid into the heater core.

 

Ok, got the new thermostat in with an 1/8th hole. Filled the block with coolant while I had it open. So, the major overheating is under control but my radiator fan is not turning on. It turns on if I ground the relay coil. It turns on if I plug in the test plug. It does not turn on with engine heat to 240. It does not turn on with the AC running. (Note: the AC had stopped cooling just before the other problems started but don't know if that is related). Trying to decide how to find out if the ECM is bad.....

 

The A/C willl only turn on the fan when the high pressure side builds pressure. With the engine idling disconnect the A/C high pressure switch connector. This will tell the ECM to turn on the fan.

If the fan comes on, then I'd look into the CTS. That is what tells the ECM the engine temperature. Note that it is isolated from the dash gauge, which can easily be incorrect. A scan tool can help with this.

If the fan does not come (with the HP A/C switch disconnected), then either the ECM or the wire between the ECM & relay is bad.

RBob.

 

also, did you use any thread sealant when you put the fan switch back in the head? its the sensor on the back side of the pass side head. i did that a while back, never occured to me that its grounded through the head, lol. that will cause some problems for you.

and when youre bleeding the coolant system, take a pocket screwdriver and put it in between the throttle and the stop to raise the idle, and even jack up the front of the car to kinda guide the air bubbles toward the radiator.

 

Mine has only a gauge sensor on the front side of the head on the driver's side, the fan switch on the intake next to the T Stat, and the pressure switch on the condensor. I am thinking at this point that either the input connections to the ECM are bad (for the fan switch on the intake and the pressure switch on the condensor) or the ECM is bad. The Test Plug does turn on the fan so the output from the ECM driving the relay and fan seems to be ok. I need to find a pinout diagram for the ECM box to see if the signal is getting there from the two sensors. I assume they are both simple switches and not variable resistors....

 

Also, I get very irratic idle when I turn on the heater or AC.. Any ideas??

 

must be different on the 3.1. ive got the one next to the t-stat too, but thats for the gauge. the one in the back of the pass side head, on the 2.8 anyway, is the fan switch.

 

dave, the 2.8/3.1 fan system is different.

3.1 has 2 coolent sensors.
left front head for cluster
one in intake for ecm/fans.


IIRC 2.8 has 3
left front head for cluster
intake for ecm
right rear head for fans.

 

youre right on the 2.8, and thanks for the clarification on the 3.1

 

not a problem, thats what were here for.

 

All's "cool" now... Fan is operating correctly... Missing ground wire from the assembly process on the back side of the passenger side head... There are three sets and I had missed one of them....