I have an 04 sr5 v8 38.ooo miles. I tow a coleman pop up camper about 2800 lbs it has trailer brakes. I towed it up to the nh white moutains this weekend with 4 people in it about 4 hour ride it was hot 90 degres. Afterthe 4 hour ride i pulled over to get gas and smoke was coming from under neath smell like brakes but when i looked it was the heat sheild above the exhaust over the rear axel smouldering away red hot i had to rip it of and throw water on it. It has stock exhaust pretty scary thing. Called toyota their going to look at it on friday.
04 4runner almost caught on fire
- Thread starter mud
- Start date
Register to hide this ad
Fourty-four
Guest
The heat shield is metal, right? How could it be burning?? Is there anything on the other side of the shield that could catch fire?
Either way, this is the first time I've ever heard of anything like this on a 4Runner.
Either way, this is the first time I've ever heard of anything like this on a 4Runner.
Fourty-four
Guest
mud said:
Okay, you just got me to go out to the garage and crawl under my 4Runner. The heat shield for my muffler is definitely metal. Looks like thin stamped steel. Nothing to burn under there!
BTW, I have an '04 4Runner, so I'm not sure if they changed the material for other model years.
Fourty-four
Guest
I read your post again, and I see that you were not talking about the muffler heat shield.
I do have that same thing where the exhaust pipe goes over the rear axle. It's not a heat shield though.... I'm not even sure what that piece does. Maybe sound-deadening material if the suspension bottoms out and the pipe hits the underbody?? I dunno, but either way, I don't think it would cause the vehicle to burn up considering that it's not very big and there's really not much else to ignite near it.
You said it was "smoldering", which makes me think that it might be made out of a material that doesn't ignite easily.
I do have that same thing where the exhaust pipe goes over the rear axle. It's not a heat shield though.... I'm not even sure what that piece does. Maybe sound-deadening material if the suspension bottoms out and the pipe hits the underbody?? I dunno, but either way, I don't think it would cause the vehicle to burn up considering that it's not very big and there's really not much else to ignite near it.
You said it was "smoldering", which makes me think that it might be made out of a material that doesn't ignite easily.
TechWrench
Senior Member
Without more to go on, the most likely cause was the fuel mixture was too rich. This will cause the catalitic converter to overheat as it burns the unburned fuel coming from the engine in the exhaust. I have seen some cats actually glow red when this happens. If the cat was overheating for most of your trip, some of the excess heat could have accumulated in the pipes and this set off the insulation material. Also, if you had any rust through hole in that area, the exhaust leak might have caused it. Either way, I'd have it checked out.
Fourty-four
Guest
TechWrench said:
Not very likely for two reasons:
1 - A new 4Runner running too rich is not very common. If it were running rich, it would throw a MIL and he would have known there was a problem.
2- This happened toward the end of the exaust system, near the rear axle. If the cats overheated, they would have to be hot enough to turn the entire exhaust system red hot to burn the piece he was talking about. Sure heat can transfer down the pipes, but even a red hot header will have nothing but a warm exhaust tip.
TechWrench
Senior Member
Fourty-four said:
I agree it isn't common for them to run that rich, but as I understand it, one of the main by-products of a too rich condition is the sulphur smell from the exhaust, along with the overheating condition in the cat. The problem with the sulphur smell has been well documented. If not from burning excess gas in the exhaust, then what is causing it? And if the sensors or ECU were calibrated purposely to allow somewhat of a 'rich' condition because of a design requirement, it may not have been bad enough to 'throw a MIL'.
As for the pipes getting hot enough to set off the underbody insulation, I also agree that it doesn't sound normal. But, what other heat source could be over the axle in that area. He did say it was right over the exhaust pipe, so that would seem to be the likely cause. He also said it was a 4 hour trip, uphill, under load. That would be a likely canidiate for the vehicle to be running rich.
Without being there, one can only take a guess on what may have happened, based on probable causes. Without any more info, I still see cat overheating as a possiblity.
greasefingers
New member
This is a very strange issue and I do not see how the dealer would be able to reproduce it. However they might have a method to check for a restriction in the exhaust system, which is the only way I see for it to glow. The engine runs rich on many occasions: start-up, acceleration, & WOT, however it will never run rich enough to cause that kind of heat. Maybe a squirrel crawled up into the tail pipe 
TechWrench
Senior Member
Along the line of a possible 'rich' condition, maybe a sensor has failed or is reporting a false a lean condition which could cause the ECU to overcompensate and run rich.
greasefingers
New member
I know the O2 sensors fail a lot on the V8 engine. They can also drift and cause a lean condition, but you would need them to scan the sensors for that. Cleaning the MAF is important. I do this every 30 k miles.
