Looking for advice. I have a 91 Firebird 305 tbi. It has been hard to start for years. The culprit wound up being a bad coolant temp sensor (next to thermostat). The guy at the parts store told me to wrench it all the way into the hole. Several other people have said that it is not supposed to go all the way in. I am hoping that I haven't damaged the intake. Any thoughts/opinions on this?

 

It's pipe thread which is tapered as is the sensor. It is the interference fit between the two that seals So screw it in till it tight how deep it goes depends on how deep the thread was cut in the manifold, it varys, use sealant f you like I do. don't overtorque you will strip the threads or break the sensor. So if it's not leaking and works you did no damage.

 

Thanks. That is what I am hoping for. I am going to let it warm up when I get home, and pray there are no leaks.

 

I've never personally heard of a coolant temp sensor causing a hard start but I suppose its' possible. I'm pretty sure it's only used for telling the ECM when the coolant is warm enough to go into closed loop.

 

The code I was getting was 15. I was told this meant the coolant sensor was reading temps below -27 degrees(I think). I didn't think this was the cause of the hard starts. But I was told if the ECM thinks the engine is that cold it provides a very rich fuel mixture. I would have to pump the gas and turn it over for a couple of minutes before it would fire, and then rev it for 5 more minutes until it warmed up for it to idle properly. Once I replaced the sensor, it starts right up and idles fine.

 

I got home yesterday, let the car warm up for a while, and saw no leaks or cracks. Should I chance backing the sensor out and putting it back in, replacing it with another, or just leave it alone? I appreciate everyone's help with this.

 

If everything seems to be running fine and you're not leaking, I'd leave it alone.

 

"The guy at the parts store told me to wrench it all the way into the hole. Several other people have said that it is not supposed to go all the way in."

THAT guy at your local parts store needs to learn a little bit about pipe threads!! You NEVER bottom out pipe threads if they are cut right. Straight threads with a sealing O-Ring, yes.

 

I probably should have not listened to the kid at the store. I should get the dumba** tax for that one. If I had thought about what I was doing for a split second, I would have noticed that the top two threads on the old one were dirty from being exposed. That's what I get for not paying attention.

 

At first glance, I thought the threads were straight. That is why I screwed it all the way in, even though it was very tough to do so. After taking a close second look, I can now see a very slight taper to the threads on the old sensor.

 

the only thing that matters is that it doesn't leak and it works... so don't screw with it..

 

Thanks. Sounds like good advice. Hopefully it will hold up.

 

Can this sensor be used to run an aftermarket temp gauge?