My EGR is pure POISON

[Junk]

Some days I swear my truck has inherited my karma. :whoops:

Went out today and the ce light comes on. I'm like what now (I'm only 1 day away from being street legal for the first time in over a year). P0401.

Pop the hood and my EGR modulator hoses are all off and the thick one in from the bottom is slight melted.

Pull out the EGR modulator and it took the below pic.

Only thing I can think of that would cause this is the other day I drove about 10 minutes with the entire exhaust system off, from the manifold on back. Obviously with the blower and the 1FZ-FE, things run hot, but I figured it would only be hot down there.

Could that have caused this?


I did not check my EGT when running exhaustless, but I checked it today and I'm not hot at all.

 

[Beowulf]

Is that the 'white' filter material that has melted? What is that?

-B-

 

[Junk]

No, that's the outside of the modulator, bottom view. Filter material did not melt.

 

[Beowulf]

It took a lot of heat to melt that plastic and the hose. A LOT of heat. Check other hoses and things in that area like the engine wiring harness. I know yours is wrapped well with heat tape but you need to take a look.

I would be very interested in theories but I don't have any suggestions other than your guess.

-B-

 

[cruiserdan]

I wonder if the EGR valve is compromised and is allowing exhaust gass to get to the modulator. That is my guess.

 

[Junk]

Yes, will be checking everything. The last time this happened, I had been pushing my truck hard to get to an event (hot day, 36" swampers and rolling way faster than any sane person would have). Later that day, Robbie, who was attending CMCC with Christo, diagnosed it as my fan clutch went bad and was making my truck run hot.

Right now the truck isn't running hot and the fan clutch seems to be ok, so the run without exhaust is my only guess. It's a little too convenient to think anything else as my truck has not been driven a lot recently.

 

[Junk]

I wonder if the EGR valve is compromised and is allowing exhaust gass to get to the modulator. That is my guess.

Don't know if it matters or not, but will mention anyway, I have a newer EGR valve on there (put it on several months ago - maybe about 5).

 

[Beowulf]

Check the big 32mm (?) nut where the exhaust pipe attaches to the EGR valve. You know the one.

If that thing came loose you would be spewing heated exhaust directly at the modulator and that hose that melted. Just a guess.

-B-

 

[Junk]

Thanks B, will check it.

 

[IdahoDoug]

I'd say it was the exhaust heat. The exhaust pipes funnel away heat rapidly before it can transfer heat to nearby components. Without it, a tremendous amount of heat ends up in the engine bay rather than farther back. Bummer, but the good news is you'll likely be fine once the exhaust is on and a new EGR is in place.

DougM

 

[yomama]

Junk,

It could very well have been caused by removing the exhaust. Your Cat converter has two purposes. 1. Burn unburned fuel. 2. Dissipate heat. Without it connected, heat doesn't just blow out, it causes other parts before it to get hotter then normal. As you have now learned....

Yomama

 

[semlin]

wow, ugliest modulator failure yet. I am pretty sure that's was caused by the open exhaust. You would do well to check everything else around the manifold too, especially the air intake bellows, PCV hoses and heater core hoses (the two that run under and through the throttle body and close to the modulator would also be a worry).

 

[landtoy80]

I don't think that running without the exhust would cause this.
The EGR pipe is connected to the exhaust manifold. If anything with less restriction it should put less pressure on the modulator.

BUT
There could be excessive back pressure without the exhaust. That pressure could blow out the diaphram in the modulator.

The modulator has a diaphram in it. When the exhaust pushes the diaphram, it opens/closed the ports in the modulator.
If you diaphram is damaged (either from being old or blown out) the hot exhaust gas will blow through the modulator. If there is enough flow through it, it would melt the plastic.

On most of our bad modulators, I think there is only a small hole/crack in the diaphram, enough to only let carbon through it.

 

[yomama]

There could be excessive back pressure without the exhaust.

Other way around. Without an exhaust of some sort, you have NO back pressure.

Yomama

 

[Junk]

Ok, sniffed around for awhile. The hose that runs into the bottom of the modulator fell apart it was so brittle when I touched it. Everything else seemed like it was in decent shape. I replaced that line with some extra fuel line I had in the garage (never did do that breather extension yet :whoops: ) so we'll see how it runs over the weekend. Will keep an eye on the EGT too. Thanks for all the help.

 

[landtoy80]

I don't know if the 1fz has a problem with backfire but on the 2f I felt some backfire or suction when the muffler was off. I put my hand over the exhaust pipe and felt it suck back every once in a while.
Is this caused by when the gas doesn't fire untill the valve is open or is it whenthe gas fails to fire and it burns in the exhaust pipe?