Technical Tips > Post 84
C4 1987 Throttle Body Coolant Bypass
Vettech:
I take it all back - I lied!, there has been water on the floor, water level is low, but now not leaking, no indication of source underneath the car, but since it has stopped, its more than likely well up top.
After much looking it appears the "brass T piece" I made up to link the heater return water and KC4 return water back into the water pump side port is at fault. I'd like to say its just the hose clamps not tight enough, but since it required an in-ordinant amount of 15% Silver Solder to patch it together, I'll hazzard a guess it will be crook brazzing.
Bugga! Its under the A/C compressor, ac frame, tensioner - a job for Ron.
Maybe if I just get it out of the garage, I can then find that gallon of petrol !?!?!?!?!??......
Vettech:
Took Bob three goes to fix what I had f#'fd up, just shows how much effort I put in.
This time we hydro pressure tested the part till we got it right.
As much as I'd like to take the accolades, its all down to years of experience, a keen eye and the deft hand of Bob.
Not to mention a nice hot Oxy tip and 45% S'solder.
Thank you Robert. Now ... to stick it all back together, at least now I have the special T45 tool to remove THAT BOLT.
87Z51:
Could have saved on 4 screws
Vettech:
Ok - that looks the part.
87Z51:
--- Quote from: Vettech on November 18, 2020, 02:18:03 PM --- (Keep in mind that on C4's once started the fuel pumps power is supplied by the Oil Press Switch as a fail safe in the event of loss of engine oil pressure.)
--- End quote ---
Popular myth .
The OP switch runs the pump directly when cranking the engine over ( after it reaches a specified pressure )
Once the engine fires up , the fuel pump is fed ( in parallel ) through the FP relay controlled by the ECM .
As you can see from the factory wiring diagram , with the engine running you can disconnect the OP switch completely and the pump will still get power - supplied through the relay.
Purpose of switch is to let you start and maintain fuel pump operation should the relay fail
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