Catalytic converters causing car to overheat??

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  #1  
Old 10-30-10, 10:51 AM
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Catalytic converters causing car to overheat??

Hi, I have a Nissan Altima 4 cyl 2002. The other day I noticed the AC started loosing its coolness; I glanced at the temp gauge on the dash and the indicator was just shy of the Hot mark. I turned the AC off, which made no difference. I noted that the temp gauge intermittently moving from the Hot mark to the middle of the temp scale from C to H. This fluctuation was consistent and occurred every couple of minutes or so. I thought it was the fan; the cooling sensor and sending unit; even the radiator. Being beyond my skill level, I took the car to my usual mechanic. The next day he called and said that my catalytic converters were bad and were causing the problem. I never heard of catalytic converters causing an overheating problem. I feel I'm being taken for a ride.

Sure would appreciate your advice.
Thanks, Majac.
 
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Old 10-30-10, 01:57 PM
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you know, start with simple. check your engine belt. if you have a serpentine belt that drives both a/c and water pump, a/c has a lot of drag in it.

I thought it was the fan; the cooling sensor and sending unit; even the radiator. when you say this, do you know that temp sensor is good? it plain sounds like a loose connection or faulty sensor.
but definitely check the belt, if it is not stretched. 2002 model, 9 yo car, roughly what - 100 000 miles? about right time for engine belt replacement anyway. and i dare not to ask, if it has timing belt and if that was ever changed? no, you good, that model does not have interference engine.
oh, and by the way:
*Excessive exhaust backpressure -- A clogged catalytic converter will restrict the flow of exhaust and cause heat to back up in the engine. Other causes include a crushed exhaust pipe or a collapsed double wall pipe. Check intake vacuum at idle. If intake vacuum reads low and continues to drop, inspect the exhaust system.

hmm... you can find a buddy with a blow torch and punch a small hole in exhaust pipe before cat. then drive around and see if temperature havoc went away. if it did - well, you have your answer. if not - you have your answer either. then just weld the hole shut back.
 
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Old 10-30-10, 02:13 PM
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*Excessive exhaust backpressure -- A clogged catalytic converter will restrict the flow of exhaust and cause heat to back up in the engine. Other causes include a crushed exhaust pipe or a collapsed double wall pipe. Check intake vacuum at idle. If intake vacuum reads low and continues to drop, inspect the exhaust system.

Ukrbyk is quoting the above from the link that appears below. For your benefit, the link appears below. Simply click on it to read all it has to offer.

Engine Overheating Causes & Cures

Cooling system basics must be ruled out, before attention is turned to the catalytic converter.

Are there any computer error codes? If yes post them. Auto Zone (and similar) stores read computer error codes for free.

Is the coolant level full?

Are cooling fans operational?

Is thermostat operational? Thermostat on a string in a pot of hot water test.

Burp the system to get rid of a possible “air pocket”.

Rule out external coolant leaks via a cooling system pressure tester.

Has the system been flushed recently? If not, then it needs to be done.
 
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Old 10-30-10, 05:24 PM
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hmm... you can find a buddy with a blow torch and punch a small hole in exhaust pipe before cat. then drive around and see if temperature havoc went away. if it did - well, you have your answer. if not - you have your answer either. then just weld the hole shut back.
Why not remove the Upstream o2 sensor??????????????
 
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Old 10-31-10, 05:36 PM
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yeah, but it will cause hell of a racket, plus he needs a special socket to do so. small hole in the exhaust does very little noise, just a putt-putt. but i guess, for the purpose of scientific experiment, he could do that either. how long does it take engine to get to overheating phase - 20 minutes? hood's gonna love him driving around with that noise....
 
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Old 10-31-10, 06:24 PM
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I doubt it's the cat. A clogged cat will almost always result in the check engine light illuminating with a O2 sensor code.
 
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Old 11-05-10, 07:18 PM
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Cat plugged

You can chec the cat by pulling the o2 sensor and plumbing in a low press gauge. If its over 3 lbs the cat is plugged or you have some other ex restriction.
 
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Old 11-06-10, 05:56 AM
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That the AC loses its coolness at the same time the engine starts to run hotter is either a large coincidence or an indication there is an obstruction of air flow through the condenser and radiator.

Years ago I was driving in freezing rain/snow in my 400E - many small slots in grill for air to enter. I noticed the air in the car getting stuffy which it should not do when the AC is on. The engine temperature was also a little bit higher than normal. The AC was on to prevent window fogging by reducing humidity of air entering passenger compartment. I stopped the car and walked around to the front. The grill was plugged with slush.

So, check to see if air is properly passing through your condenser and radiator.
 
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Old 11-06-10, 07:49 AM
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Originally Posted by HotinOKC View Post
I doubt it's the cat. A clogged cat will almost always result in the check engine light illuminating with a O2 sensor code.
also, there will be significant power loss due to exhaust backup. and i mean - significant, to the point you can't drive up the hill. sorry to repeat myself, but i have been there either. and guess what - that - yes, ford taurus - could not climb the hill, cat was in shattered pieces - but temp was just fine.
 
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Old 11-06-10, 09:15 AM
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Originally Posted by LawrenceC View Post
That the AC loses its coolness at the same time the engine starts to run hotter is either a large coincidence or an indication there is an obstruction of air flow through the condenser and radiator.

.
On almost any recent car (2000+) the computer tells the A/C compressor to disengage if the car starts to overheat. Same thing happens when you floor the gas pedal.
 
  #11  
Old 11-06-10, 09:39 AM
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Car was not overheating. It was well within the normal range but higher within the normal range. Car was 1993 vintage.
 
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