Oh Crap-CHT sensor replacement bogged down by

[tshih]

Guys,
what suggestions do you have for freeing the old rusted on CHT sensor on a 1988 Carrera 3.2. I've read and tried the posted threads on this forum and have gone through 2 deep well sockets (13mm) modified by grinding a slot down the side for the sensor wire. The problem is the old sensor was not properly gripped by the socket tools and the 13 mm socket appears to have rounded off the outside of the sensor head.

I have 2 possible approach to try going forward,

1. PB blaster for several days followed by heating with a pencil torch

2. drill out the old sensor and re-tap

Any other better suggestions are welcomed.

TIA, Tom

[john walker's workshop]

first, mix up 50/50 acetone and atf, wet it down and wait for a day. then cut off the wire and use an uncut 3/8 drive 6 point deep socket, looonnngg extension and ratchet. the new ones are 14mm, so you will have to notch a socket for that. do not over tighten or you may shear off the new one.

[Targa Me]

i strongly recommend you DO NOT try to drill out the old sendor.

[stlrj]

Tom,

I was just wondering. What was the reason to replace the CHT on your '88? My understanding was that your '88 already had the new style two wire sensor. Was yours testing bad?


Cheers,

Joe

[tshih]

John
thanks for the advice, will try that today when I get home.

Drilling will be the last resort.

Joe,

The surprising thing I discovered is the old sensor was a 1 wire 13 mm head one.
The wire was broken off during my early attempts at extricating with my home modified tools. The sensor is being replaced as preventative maintenance as well as to remedy my recent un-intended acceleration (fast idle-redline) problem when the car got hot during stop and go traffic. I was going to refresh the idle micro-switch, throttle position sensor, idle return springs, and CHT. But that will be another story after this first step is solved.

[tshih]

Well, the top of the sensor appears to have been rounded off so the 13 mm wrench doesn't have any grip.

What next? Vice grips?

Any special extraction tools that works like a filter wrench which grips as you turn?

[kidrock]

maybe gently tapping a smaller diameter socket over the offending part? (12mm or 15/32") Kinda risky, tho...wouldn't want to bang too much and damage something.

[john walker's workshop]

1/2" is a hair smaller than 13mm. there are nut/bolt removal sockets that have sharp, spiral teeth. you get one that just barely fits over the edges of the fastener, hammer it on further and carefully apply twist. usually works. you can also take a small piece of cloth, place it on the fastener and hammer a socket on. takes up some slack. works sometimes.

[jimbauman]

Are you trying to do this with the engine in the car?
JB

[Kidasters]

I just did it with the engine in the car. The rubber grommets are a pain, but otherwise, it's not that bad.

[tshih]

I will buy a 1/2" bolt extractor and try that first.

Yes this is being tried with engine in car. Otherwise it's no real challenge.

[john walker's workshop]

these kits are not very expensive. don't know if you can buy just one piece.

[Targa Me]

John, those are cool... i'm gonna need to get me a set. Don't need 'em now, but when you do...
Looks like those are Blue Streak (Snap-On).

[burgermeister]

Just cut the wire & use an un-slotted 6pt 1/2" socket. Sometimes a bit of valve grinding compound on the offending part helps the socket grip better.

You only need the slotted 14mm socket to put the new sender back in, and the torque is really small. You probably rounded it off using the slotted 13mm socket, which will expand if it sees any substantial torque.

[tshih]

Guys,

Got the old sensor head out! Bought cheapo Harbour Freight extractors ($30) and save time not having to drill and re-tap head.

Thanks John for the best advice.

Happy Memorial Day weekend.

Tom

[jlpintl]

How about if I broke off the top and the threads are still in the head

[jmh61]

I had the same experience. Old CHT snapped when I tried to take it out.

At that point I figured I could either try and drill it out by hand or drop the engine. I figured I would try and drill it out by hand first and avoid the engine drop. If it didn't work I could always drop the engine.

I ended up drillinig it out with progressively bigger bits. Like 1/64 of an inch at a time. Then I used a tap to clean the threads. Tap size is odd. Can't remember what size it is, but do remember getting the size off this board. You can probably find it with a search.

Drilling was a high pucker factor moment, but the bottom line is that the drill out worked.

[john walker's workshop]

12x1.00

i've had a new one snap like that. didn't take much effort either.