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Blazin carpet by muffler on 95.

D

dyna

NAXJA Forum User
Location
central coast Ca
This sounds dumb but here goes. We just got back from the sierras and on the way up we kept smelling something real hot. finally tracked it to the floor boards and carpet above the muffler, not the cat. Hot enough to char a couple of cable ties under the seat area and make things so hot it would burn your hand to grab tools. We were climbing in 1-2 range at 20 mph or so loaded up with gear and kayaks and now running on 31`s and never went off 210 degrees. Can it bet the xtra load etc just made it to hot down under? Damn, if there was a can of tire fix or? under there it woulda blown up I think. Anyone have this happen?
 
yep mine does the same thing.....it gets extremely hot there to the point that it will burn you, and after driving for a while smells like burning....which i have figured out is coming from that spot....
 
dyna said:
This sounds dumb but here goes. We just got back from the sierras and on the way up we kept smelling something real hot. finally tracked it to the floor boards and carpet above the muffler, not the cat. Hot enough to char a couple of cable ties under the seat area and make things so hot it would burn your hand to grab tools. We were climbing in 1-2 range at 20 mph or so loaded up with gear and kayaks and now running on 31`s and never went off 210 degrees. Can it bet the xtra load etc just made it to hot down under? Damn, if there was a can of tire fix or? under there it woulda blown up I think. Anyone have this happen?
Click to expand...
That sounds like something that needs fixed before you have a fire, it should not happen.
The cause is, rich un-buirned fuel, air leaks in the exaust system, or geared to high for 31"

To test for a plugged converter, drill a small hole in the exhaust pipe right before the catalytic converter. Install a temporary hose fitting and attach a long rubber hose and a 0 to 10 pound pressure gauge. With the gauge inside the car, drive up a hill or accelerate and read the pressure. Normal is 2 to 3 pounds, restricted 4 pounds or higher. The drawback to this method is the small hole will need to be welded shut after the test; a minor job if you have a welder.
 
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I've not had my carpets burn, but I've certainly experienced bottled water too hot to drink after lying on the floor above converter/muffler area! Pulled the carpets and found the paint craked & scorched. I bought high-temp insulation from Summit Racing. Used the pad type to replace the factory padding under the carpet, over the converter/muffler, and used the "peal and stick" reflective style under the floorboards between the header pipe, cat/muffler and the floorboards. This did wonders for the interior heat problem. But, even though I completely cleaned the sheet metal in the area where I applied the stick-on reflector--it's come loose. So if you use the skicky stuff, I'd suggest sheet metal screws, or some other means to mechanically hold it inplace. I added the new insulation in conjunction with installing a "Cheby", with larger exhaust system that sets much closer to the floor boards. So far, so good.
 
Not sure if anything is wrong, as far as the engine and fuel mixture goes. Cats run extremely hot when fuctioning correctly. Put them too close to the floorboards and you can't help but transfer that heat into the cab. The same goes for a muffler mounted close to the floor boards. I know what your saying--if your running too rich of a mixture, the cat works harder, but WILL eventually fail. If that happens, you'll not pass a SMOG test. So, short of capturing ECM data showing fuel mixture at various RPM/Load conditions, how would you know if your running too rich?
When I had the 4.0 installed, I considered all was OK because I passed my semi-annual SMOG. The one time I didn't was do to a lazy O2 sensor. Of course, a bad O2 sensor could easily cause an engine to run too rich--or lean.
It seams this overheated floor board problem is commom among XJ's--at least early 4.0 XJ's. I've noticed newer cars have lots of reflective type insulation installed under the floor boards, near exhaust components. Also, the classic symptom of a clogged cat is significant loss of power. I had that happen, as well.
 
The Cherokee's 11 years old, I understand what your saying but I have to believe if it were normal it would have caught fire long ago. The heat suppose to be in the Cat not back in the muffler. There are plenty of heat shields where it's normial to get real hot.
 
Do you have the stock cat or an aftermarket one? The reason I ask is that now that I have a high flow aftermarket cat my passenger side floor gets very very hot when it didnt use to. I think its becuase my aftermarket high flow cat doesnt have a heat shield like the stock cat did.
 
My son's 96 has a rotted out place under the back seat from the heat from the muffler. However on my 99 there's a aluminum shield mounted on the body between the muffler and body.

JoBo
 
My assumption has always been that the heat shield is there to protect you from starting fires below,... not above the cat like when you park on top of dried leaves in the Fall. That's why I have my heat shield facing down, away from the body. Is this wrong? I don't think so but could be.
 
Having same problem, here's my thread:
http://www.naxja.org/forum/showthread.php?t=63051
Here's what I've come up with: I looked in my "94-96 Parts" manual and it did not list any type of exhaust heat shield for the XJ. I looked in a 2000 FSM and gave installation/removal instruction for a muffler heat shield. I called a dealer and he didn't list and exhaust heat shields for a '96 or '00. This afternoon I'm going to try to find a couple newer and older XJs on car lots and look under them. I'm betting a heat shield is what we need though.
 
heat shield part number: 55235811

DSC00051.JPG


HTH
 
Is that a dealer part number?
 
Sorry for the repeat but how much was it?
 
dyna said:
Damn, if there was a can of tire fix or? under there it woulda blown up I think. Anyone have this happen?
Click to expand...

Good discussion already. Not much to add. This thought made me stop, though. A college buddy of mine did that in a VW bug. Packed it to the roof leaving his parents house for the start of the winter term. After about an hour driving, he said, there was an ear ringing BANG and the entire cab was filled with black snow. He had packed his emergency road kit on the floor behind the front passenger seat, right in front of the heater vent that comes out under the rear seat. Insulated under all his cloths and junk that area got hot. Fortunately, the stuff packed on top of the fix-a-flat can caught any shrapnel but the fix-a-flat compound was blown into the cab and vulcanized in the air. I know I've seen this as an urban legend as well, but I can attest to the aftermath of at least one "black snow" event.

Remember, radiant heat is transfered as the inverse square of the distance. If the muffler is just a little bit closer than spec it will transfer heat to the underpan at a much higher rate. Also, at low speed there will be less convective heat taken away by the air. Still, it's worth checking on the mixture and the condition of your cat, as stated above.
 
It seem's to me we are descussing two different things here.

It is normal for a working Cat to get very hot, some OEM models have the heat shield built in and others don't.

However the carpets burning way back by the muffler is not normal.

The guys that have replaced their OEM with a high flow have just replaced a non-working Cat with a working one.

The cat is there to burn un-burnt fuel, when there’s so much un-burnt fuel the heat burns the carpets under the back seat you have a problem.
 
I will admit that ever since I replaced the fan clutch and had the radiator done and installed a trans cooler it now runs at 195/210 on the guage. I know it will go higher due to the reads prior to the repairs where it was gettin to the red, so now Ive noticed more soot on the tail pipe tip which made me thinks it was running rich. Fully loaded Im still gettin 15 mpg and 16/18 empty, But if that was the case and things were out of wack wouldent my engine light be on? say a failer 02 sensor or?
 
dyna said:
I will admit that ever since I replaced the fan clutch and had the radiator done and installed a trans cooler it now runs at 195/210 on the guage. I know it will go higher due to the reads prior to the repairs where it was gettin to the red, so now Ive noticed more soot on the tail pipe tip which made me thinks it was running rich. Fully loaded Im still gettin 15 mpg and 16/18 empty, But if that was the case and things were out of wack wouldent my engine light be on? say a failer 02 sensor or?
Click to expand...
My 87 is getting 21/23 16/18 is way low.
 
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