99 Jimmy "clicking" behind glove box

Hey, I just bought a 1999 jimmy 4x4 4 button, I could hear a clicking from behind the glove and found a relay ti be constantly be clicking but seems to go away when the brake pedal is pushed. Also had P0740, trieed to clear but must be a hard fault, comes back after a coulpe key cycles? Plus I noticed coolant on the top left if the engine leaking... are they know for intake gaskets?

The clicking might be the turn flasher caused by dirty contacts in the multifunction switch. There is a thread in the Blazer "How-To" section that explains how to clean them. The multifunction switch is expensive to replace so cleaning it is worth a try.

The P0740 indicates a problem in the Torque Converter Clutch, (TCC) circuit. Could be wiring or the solenoid inside the transmission.

The 4.3L is very well known for lower intake manifold gaskets to leak coolant...and oil...and vacuum. Felpro makes a redesigned gasket (MS98002T) that will permanently fix the leak(s). There are several threads in the Blazer "How-To" section that will "walk" you through the repair.

So yeah that was the right idea.... I just finished the lower intake gaskets and now is a no go? P0336 is set, I took the fuel pump relay out and cranked her over to flush out the coolant.... now seems like theres no fire.... should also mention I replaced the plugs, wire, cap and rotor??? Pretty sure the distributor when back in the same way it came out also.

P0336 is a problem with the crankshaft position sensor, that's why you're not getting spark. Follow the wiring from the sensor and make sure everything is plugged in correctly.

So it turns out the rotor button had an open in it!!! My fault, should have paid for OEM... Thanks for the help.

An "open"??? Please explain.

no continuity...

The ignition coil has ample voltage to jump a half inch gap. Even if the rivit that holds the rotor tip on was loose, it wouldn't cause a no start condition, and it certainly wouldn't cause the P0336 to set. The P0336 is set when the ECM doesn't receive a signal from the crankshaft position sensor. The CKP sensor data is what the ECM uses to fire the ignition coil. Did you check all of the connections for the CKP sensor? Is the Service Engine Soon light on?

I'm not sure why it was that way... the only thing I did was swap rotors... the MIL is on but only with P0740

That's odd.... If the P0336 is set in the future, check the circuits for the CKP, it's only thing that will set that DTC.