Is a bad catalytic converter causing my high engine temp?
07-06-2002, 04:38 AM
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Is a bad catalytic converter causing my high engine temp?
My 944S2 has 115,000 miles on it and I have replaced the entire cooling system on it trying to get the engine temp to normal. Right now it climbs to the last white mark on the gauge and sits there. Both radiator fans work as advertised and the temp sensor is new. I am thinking that my cat is stopped-up causing the temp to rise. The car also, for the last 2 months, has been needing 2-3 start attempts to get it running when the engine is cold. My mechanic thought it might be a faulty head gasket so I just replaced that last week. The old gasket looked like it was in good condition and the new gasket didn't make any difference. Please, any suggestions?
07-06-2002, 02:27 PM
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When the temp is reading that last mark...hit the AC button (but dont turn on climate control...just hit the AC button..this engages both fans) and see if the temp comes down.
If it does, its fan related (just want to verify you are getting high speed of the fans).
If not, have you bled the cooling system thoroughly? Try adding a bottle of Redline Water Wetter to the mix. Is the radiator clean (the outside of it)? Does the radiator flow OK?
What are the temps outside when the car is running that warm? Does highway driving vs. around town have any effect? Does the temp gauge move around or hold steady at that bar? (mine creeps up when i slow down and drops once i get on the highway and start moving). Maybe it is an electrical problem...and your temp actually isn't that high.
Hope this helps some...
--Adrial
If it does, its fan related (just want to verify you are getting high speed of the fans).
If not, have you bled the cooling system thoroughly? Try adding a bottle of Redline Water Wetter to the mix. Is the radiator clean (the outside of it)? Does the radiator flow OK?
What are the temps outside when the car is running that warm? Does highway driving vs. around town have any effect? Does the temp gauge move around or hold steady at that bar? (mine creeps up when i slow down and drops once i get on the highway and start moving). Maybe it is an electrical problem...and your temp actually isn't that high.
Hope this helps some...
--Adrial
07-06-2002, 02:56 PM
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Dave:
Usually the opposite occurs. If the engine is running lean and/or hot, you'll cook the cat. and fail the smog test (esp in California).
Adrial had some good tips. Also, just behind the driver's headlight is where the A/C elec. lines connect. If you unplug one of those connectors and turn on the A/C, the A/C compressor will not turn on, but your fans will (a little Autocross trick I use for hot track days). See if that will lower your temp.
Bleed the coolant system a couple of times. I've noticed that even after bleeding my system a bunch, I can still get MORE air out if the system on hot days! Periodic coolant system bleeding is one of my maintenance rituals now. It takes seconds (okay minutes) to do, is very easy, and can only better your system ~(;-D.
Finally, what thermostat did the shop install? I run 180'F. in mine, and recommend 160'F. if you live in humid climes. If you're running a higher thermostat, switch it. Otherwise, you're overworking your fan relay and fan motors. Yes, a thermostat switchout is an ugly job, but it will do the motor heaps of good, in my opinion.
Bon Chance! <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
Usually the opposite occurs. If the engine is running lean and/or hot, you'll cook the cat. and fail the smog test (esp in California).
Adrial had some good tips. Also, just behind the driver's headlight is where the A/C elec. lines connect. If you unplug one of those connectors and turn on the A/C, the A/C compressor will not turn on, but your fans will (a little Autocross trick I use for hot track days). See if that will lower your temp.
Bleed the coolant system a couple of times. I've noticed that even after bleeding my system a bunch, I can still get MORE air out if the system on hot days! Periodic coolant system bleeding is one of my maintenance rituals now. It takes seconds (okay minutes) to do, is very easy, and can only better your system ~(;-D.
Finally, what thermostat did the shop install? I run 180'F. in mine, and recommend 160'F. if you live in humid climes. If you're running a higher thermostat, switch it. Otherwise, you're overworking your fan relay and fan motors. Yes, a thermostat switchout is an ugly job, but it will do the motor heaps of good, in my opinion.
Bon Chance! <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
07-06-2002, 03:30 PM
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What about a candy thermometer in the coolant to verify?
I second the 160' thermostat and low temp fan switch. mine never gets past the 1st white line ( 8 O'clock position) even in slow traffic, and surprisingly my oil consumption after 2000miles on a change went to none-damndest thing I ever saw.
Good Luck
I second the 160' thermostat and low temp fan switch. mine never gets past the 1st white line ( 8 O'clock position) even in slow traffic, and surprisingly my oil consumption after 2000miles on a change went to none-damndest thing I ever saw.
Good Luck
07-06-2002, 03:58 PM
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triscadek, that sounds like its running a little TOO cool for my tastes...
What's your oil pressure at idle when warm?
A low temp thermostat will only slow down your warm up process...it won't make the car run cooler to the best of my knowledge.
Oil consumption is interesting though
What's your oil pressure at idle when warm?
A low temp thermostat will only slow down your warm up process...it won't make the car run cooler to the best of my knowledge.
Oil consumption is interesting though
07-06-2002, 05:00 PM
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Oil pressure is 2 1/2 to 3 bars, it went up from 1 bar. I also use Lucas oil stabilizer.( that stuff in the parts store where you play with the oil and gears)
After 2000 miles I would consume 1 quart every tank of gas, about 400miles or so-now I do 3000miles and don't use any.
I told my mech. about this and he just said Oh yeah, and something about the top end not using it at a lower temp./thicker oil.
My temp. gauge would previously always sit at the 2nd white line and enter the 3rd field in slow traffic.I just got tired of watching that needle so close to the red and so far from the cold mark.
It still heats up about the same and I get roast you out HOT heat in the winter.
I had thought about doing a post on thatBut decided I didn't want to hear that it was bull**** or I was a kook.
I'm the first to admit that it sounds farfetched to me too, but it works.
BTW on the bad cat ?
I have not heard of a bad cat. overheating a car. but I have seen poor performance under load and a floorboard hot enough to boil water on.
After 2000 miles I would consume 1 quart every tank of gas, about 400miles or so-now I do 3000miles and don't use any.
I told my mech. about this and he just said Oh yeah, and something about the top end not using it at a lower temp./thicker oil.
My temp. gauge would previously always sit at the 2nd white line and enter the 3rd field in slow traffic.I just got tired of watching that needle so close to the red and so far from the cold mark.
It still heats up about the same and I get roast you out HOT heat in the winter.
I had thought about doing a post on thatBut decided I didn't want to hear that it was bull**** or I was a kook.
I'm the first to admit that it sounds farfetched to me too, but it works.
BTW on the bad cat ?
I have not heard of a bad cat. overheating a car. but I have seen poor performance under load and a floorboard hot enough to boil water on.
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07-07-2002, 02:58 AM
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Adrial,
Good suggestions, but my radiator/waterpump/thermostat/belts/head gasket are all brand new and I am still chasing this problem. Could this problem possibly be due to a blocked muffler or cat? I am wondering if my fuel pressure regulator is going bad? My car is very difficult to start when it is cold and this is even after I put a new head gasket in last week at which time I had the head rebuilt since it was already off the car!! <img src="graemlins/c.gif" border="0" alt="[ouch]" />
Good suggestions, but my radiator/waterpump/thermostat/belts/head gasket are all brand new and I am still chasing this problem. Could this problem possibly be due to a blocked muffler or cat? I am wondering if my fuel pressure regulator is going bad? My car is very difficult to start when it is cold and this is even after I put a new head gasket in last week at which time I had the head rebuilt since it was already off the car!! <img src="graemlins/c.gif" border="0" alt="[ouch]" />
07-07-2002, 12:38 PM
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I doubt a blocked cat would cause an engine to run warmer than others.
Last summer mine ran between the two white marks. This spring I replaced the radiator, water pump, removed the AC condenser and removed the horizontal support on the front valence. Now it runs on the first mark only climbs halfway to the second mark in traffic (50-50 water anti-freeze mix w/ water wetter). I suspect the biggest contributor was removing the condener, there was a lot of crud between the two cores.
Last summer mine ran between the two white marks. This spring I replaced the radiator, water pump, removed the AC condenser and removed the horizontal support on the front valence. Now it runs on the first mark only climbs halfway to the second mark in traffic (50-50 water anti-freeze mix w/ water wetter). I suspect the biggest contributor was removing the condener, there was a lot of crud between the two cores.
07-07-2002, 03:55 PM
#11
I had a clogged cat on a Buick Grand National I use to have and it made the engine run warmer than usual and it started loosing power, I removed the cat and took a rod and beat the stuff out of the inside of the cat and reinstalled, it made the car run much cooler and it had a lot more power it also it looked stock for the inspection.
07-08-2002, 01:54 AM
#13
maybe a bit of clarity wil help here.
The catalytic converter is basically a box stuffed with steel wool. The heat of the exhaust reacts with the steel wool, and causes an oxidization of the exhaust gases, rendering them less volitile to the atmosphere. There are no large chunks, or pieces that could block off the flow.
When your engine blows oil, this soaks the steel wool, and thickens over time, reducing the flow rate thru the cat. If it blocks enough flow, the heat cannot escape properly out the exhaust, and this can "coke" the oil, or make it rock hard.
You could see less power, due to the reduced airflow. You can even get to the point that the engine cannot run properly due to excessive back pressure. this happened to me once in a very scary part of Atlanta.
Now you can get some retention of heat, but it also comes with a reduced engine operation rate. I would seriously look elsewhere to find the source of your overheating problem.
Try the things others have mentioned. Bleed the system till you are sick of doing it. Make sure you have the proper coolant/water mix. You do have a 25%/75% mix right? Change the thermostat. Blow out the radiator from the back, it likely has years of tiny rocks and dirt, bugs and crap blocking the vanes.
It isnt very likely that you are overheating because of a faulty exhaust component.
hope it helps man.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
The catalytic converter is basically a box stuffed with steel wool. The heat of the exhaust reacts with the steel wool, and causes an oxidization of the exhaust gases, rendering them less volitile to the atmosphere. There are no large chunks, or pieces that could block off the flow.
When your engine blows oil, this soaks the steel wool, and thickens over time, reducing the flow rate thru the cat. If it blocks enough flow, the heat cannot escape properly out the exhaust, and this can "coke" the oil, or make it rock hard.
You could see less power, due to the reduced airflow. You can even get to the point that the engine cannot run properly due to excessive back pressure. this happened to me once in a very scary part of Atlanta.
Now you can get some retention of heat, but it also comes with a reduced engine operation rate. I would seriously look elsewhere to find the source of your overheating problem.
Try the things others have mentioned. Bleed the system till you are sick of doing it. Make sure you have the proper coolant/water mix. You do have a 25%/75% mix right? Change the thermostat. Blow out the radiator from the back, it likely has years of tiny rocks and dirt, bugs and crap blocking the vanes.
It isnt very likely that you are overheating because of a faulty exhaust component.
hope it helps man.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
07-08-2002, 01:57 AM
#14
Hmm, somehting else I saw after reading again.
You have hard starts when cold, and excessive heat when hot.
What makes engine heat? Friction. (well, and fuel burning, but lets not look at that part right now)
Could it be possible that you have some surfaces that are binding? Causing the hard starts, till oil lubes the parts. And also causing the heat, as the parts are still not sliding freely, even when lubricated.
just an idea, probably not very useful.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
You have hard starts when cold, and excessive heat when hot.
What makes engine heat? Friction. (well, and fuel burning, but lets not look at that part right now)
Could it be possible that you have some surfaces that are binding? Causing the hard starts, till oil lubes the parts. And also causing the heat, as the parts are still not sliding freely, even when lubricated.
just an idea, probably not very useful.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
07-08-2002, 01:30 PM
#15
Actually Water944t, the catalytic converter has three seperate blocks of matrix that look like honey comb with really small holes. Each block of matrix is about an inch thick. The matrices are an alloy of various things including, if I recall, platinum, that catalyse the exhaust gases making them more eco-friendly. It can fail from either running too lean (gets it really hot and melts), running too rich (contaminates the matrix and clogs it up with soot, which builds up heat and causes it to melt) or oil blow by (obvious results). I know as a fact that chunks of matrix can blow out the tail pipe when a catalytic converter fails because it happened to mine.
I'll post some pictures of my failed cat as soon as I pull it off the car so you know what I am talking about. There may still be some busted up chunks inside.
I'll post some pictures of my failed cat as soon as I pull it off the car so you know what I am talking about. There may still be some busted up chunks inside.