CHT Fast Replacement Trick

[retro74]

Thanks to PP and Everyone that takes time here for helping me to narrow down my off-the-line hesitation and sudden cutoff problems.

I replaced the CHT sensor on my 1974 2.0L D-Jet car in one hour. Old CHT sensor was reading almost 2000 ohms at 75 degrees F, but it didn't change much as car warmed up.

How to do it fast?
- New CHT Sensor from PP
- Decide if you want to test the injectors, replace the intake runner hoses and lower gaskets, etc. Mine were all new.
- Tools:
Flathead and Philips screwdrivers
13mm regular socket
13mm deep socket (must be 3/8 or larger drive size)
Socket handle
Short socket extension for 3/8 drive
Small-medium vise grips
Contact Cleaner in a spray can (Home Depot or Radio Shack)

About that 13mm deep socket:
- Husky and Stanley 3/8 drive brands are short
- Craftsman 3/8 drive are @ 1/2" longer
- Craftsman 1/2" drive is even longer and it is tapered at the tip for tighter holes.
- I had shorter Husky and it was just barely long enough for this method.

LETS GET TO WORK...

- Disconnect battery positive for safety.

- Removed the Decel Valve and MPS from the passenger side of the engine (remove MPS wire plug and set MPS and Decel Valve aside).

- Remove passenger side sparkplug wires from the sparkplugs and set aside.

- Remove the Intake runners from the passenger side of the engine (remove three nuts and washers against head. Remove injector hoses, injector wires -- Some fuel will leak out when hoses are disconnected). Wiggle, wiggle and pull to remove.

- Remove the rubber insulator from around the CHT.

- I assumed that the CHT sensor was not going to be too tight because it would snap if overtightened and heat from engine should have loosened it a bit over time... I was correct.

- Based on the above assumption, use the 13mm deep socket and feed the wire end all the way through the socket. Push the socket over the nut portion of the sensor (wow it almost dissapears in there) and note the angle of the socket (it is at an angle so remember that!).

- You can't use your socket wrench handle with the wire in the way, but the vise grips will grip the last 1/8" of the socket (Grip more if socket length allows). Turn counterclockwise and then reposition socket with vise grips attached. Do this 3 times and it should unscrew by hand.

- Put in the new CHT as follows... A new washer should be included with the CHT replacement and it should be slif onto the CHT. Use and a little "squish" with the vise grips (just a little) to "ovalize" the washer on the threadless base of the CHT. DON't touch the threads with the visegrips.

- Use the contact cleaner to BLAST away any oil or debris in the CHT socket. We do like good grounds now don't we...Hmmmmm?

- Feed the new CHT wire through the 13mm deep socket and use the same angle (you did remember the angle right?) to screw in the new CHT sensor. Hand tighten.

- Again use the Vise Grips on the outer edge of the deep socket to tighten. NOT TOO TIGHT! I use my pinkie on the end of the Vise Grips and didn't force myself to feel pain (some of you are into that and have MG's or Alphas too?).

- Reconnect everything. Intake runner nuts should be tightened down 1/10 turn at a time and NOT overtightened. BUT, you should recheck the tightness after 100 miles or so if you used new gasket/blocks, but again be sure to gently torque them 1/10 turn on each nut to avoid warping.

- Plug the CHT sensor into the wiring harness. Is the electrical spade on the harness OK? If not replace with a new one. I put some shrink wrap over the CHT connector to prevent shorting and I let the engine proivide the heat (now THAT is easy and I didn't need to sneak my wife's hair dryer into the garage...)

- Make sure that the injector and MPS wires are connected.

- Check the fuel lines after it's all together again and under pressure. I also checked to make sure that the P.O. had used real fuel line hose clamps (smooth inside) and not hardware store clamps that would allow the ridges to damage the fuel lines. Mine were correct.

- Reconnect the battery

- REJOYCE, you didn't need to remove, bend, scratch and mutilate your engine tin!

ENJOY!

Joe

[This message has been edited by retro74 (edited 09-09-2001).]