EGT questions and a near-calamity

[derekja]

I have some EGT questions. Also a new near-calamity that I'd love some thoughts on...

1) my EGT probe is in my passenger side exhaust manifold at the back. What kind of maximum temperatures do I want to see? I hit up into the 800 kind of range running unloaded up a hill on the freeway, does that sound about right?

2) At between 800 and 900 my pyro flips out. It jumps to the top of the gauge then the bottom and just goes crazy. When I let off the gas and the EGTs come back down to around 800 it returns to normal. Any ideas why? I presume this is just a gauge or probe issue instead of things really getting super hot as soon as 800 degrees is crossed... Is replacing the probe the first step?

I did a few searches and couldn't find this EGT info, but I know I've seen a post about it before...

Now the near-calamity... I had Midas weld back on my exhaust since I don't have any welding equipment. I was also running out of time so I had them replace the rear brakes. Mistake. I picked the truck up from them, put a bunch of miles on it to break the new engine in, then put my truckbed camper on the truck. About 10 miles later, on the freeway, my right rear wheel came off. Right on the highway, pop. It was the scariest thing ever. I ground across two lanes of traffic on the axle before coming to rest on the side of the road. Midas admitted that they had torque'd the lug nuts to 90 instead of 140. How scary is that? Half of the lug nuts sheared, the other half backed out but didn't shear.

They replaced the mangled wheel and pulled apart the right rear brake again to inspect the seal and everything and said that it was all fine. They're covering the repair costs, of course, since it was their fault for not tightening the lugs properly. It drives fine, but I'm a bit skeptical of their claim that nothing else was damaged and will probably take it to another shop to confirm.

[daustin]

Damn that would make me leave a brown spot on the seat!!!! I had that happen in the mid 80's on a GTO is used to have, RR came off and i went
sliding around an intersecion. Didn't hit anything but scared the crap out of me. Good to hear your ok, i'd take the rears off and look at them personally after that.
Don

[gmctd]

Check all your electrical connections to the EGT gage, incl the probe wiring - that would give the symptoms you posted - well....all except the wheel coming off..............

[Robyn]

After you check the connections if it still gets hinky the issue is most likely the probe itself.

The thermocouple is based on two disimilar metal wires that when exposed to heat produce a small electrical current.

The probability is that there is a temperature induced failure in the probe at around the temp you see it go whacky.

It could even be the gauge but I would suspect the probe first.

The numbers you are seeing are fine.

The "Crispy Zone" is above 1050F :eek:

Never get caught driving in the crispy zone :D
A very short excursion into this area wont hurt anything but more than a short (15 seconds) is gonna take its toll.

Having the timing just right as well as injectors that are right up to par is a good way to fly on a turbo engine.

Crappy injectors that pee a stream or dribble can lead to a meltdown.

Oh BTW, Midas should be paying for a new pair of shorts too. :rolleyes:

Maybe even a new box of wits as you were probably scared out of yours :eek:

Also, next time your at the parts house you may want to get a small aerosol can of pucker remover for the seat too. :D

Unfortunately what you went through is not all that uncommon.
So many shops turn out very unsafe work.

Recently our little explorer (YUCK) started making a nast grinding noise, I investigated to find the both retaining bolt that hold one of the rear brake calipers has been left out when the brakes had been done.

Whoever had done the brakes before we got the car was responsible.

Just makes me very angry that this crap happens, no excuses for sloppy repairs at all.:mad:

Glad you got through safely :)

Robyn

[derekja]

sigh. just wanted to update on this one in case anyone else runs into similar problems.

The pyrometer issue was with the probe. It's an autometer pyrometer, so I ordered a new probe, part #5249. It came and didn't work. I sent it back and got another one. Same symptoms. As soon as I started the engine it would swing down to below zero and stay stuck there. The old probe continued to work fine up to about 800 or 900 degrees.

I finally found a tech at autometer who was able to tell me that for a period of time their pyrometers were using non-grounded probes, and that the new probe I got was a grounded design and that the gauge needed to be upgraded to accomodate it. I'm sending it in and they're upgrading it at no cost.

BTW. got the rear end checked out by a different shop just to reassure myself that midas hadn't missed anything. No damage from the wheel incident. I find it kind of amazing that I could slide several hundred feet without a wheel on the rear axle in a fully loaded truck and not have anything damaged. Not that I'm complaining!