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heating fan prblems and failed smog on NOx


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18 replies to this topic

#1 nathan.chase

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Posted 31 July 2006 - 08:01 PM

Hi everyone. I just bought a 87 gl wagon 4wd. the electric fan doesn't come and the car overheats. the previous mechanic said the waterpump needed changing but the fan doesn't come on so what did he know that I am missing. I jumped the motor and it works. I got 10 volts out of the harness going to the fan but couldn't get a repeat reading, seems to be dead now. According to the mechanic the computer is dead as well, if it is failing how can I tell? is the fan run by the computer?

the car failed emmissions on NOx and I am thinking that the overheating might be part of that seeing as I have check the EGR system and it the valve seems to be moving fine. I can still check to see if their is a clog but I am thinking the fan or computer are more likely. it passed with flying colours on other emmissions.


thanks for the help. I am a subaru newbie and love the new wheels.

sincerely,
Nathan Chase

#2 edrach

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Posted 31 July 2006 - 08:12 PM

What's the battery voltage with the car off and with the engine running? It should be around 12V DC with the car off and over 13.6 or more with the engine running at around 1500 rpm. That's one problem that might need to be resolved. Fan likely has a bad thermal switch, connector, or bad ground on the radiator as well as a possible bad fan motor. Thermal switch mounted on the side of the radiator grounds the fan motor and power should be present at the connector. Thermal switch can't complete the path to ground if the ground wire for the radiator is missing (small wire to the top valance from the top of the radiator). Poor fan operation would only cause overheating if sitting at idle. There should be enough airflow through the radiator at cruising speed to keep the car from overheating. Depending on the age of the car (or the miles since the water pump was installed) will determine whether the water pump is at fault. Try to get a copy of How to Keep Your Subaru Alive, 2nd edition. It will cover basic repairs for your '87 and help you along.

#3 nathan.chase

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Posted 31 July 2006 - 09:21 PM

Thanks for the help. I connected the fan motor directly to the battery and it worked. The connector for the fan is where I got a undouplicated voltage reading. I will test the voltage at the themoswitch in the radiator. it has two lines coming out. Is one ground? I'll double check the radiator ground.

also do you think overheating would be a cause of NOx. I am not sure how much that can influence NOx.

thanks for the reply!

#4 NorthWet

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Posted 31 July 2006 - 10:03 PM

How far off were you on the NOx? Overheating might have some effect, but depending on what mode was tested/failed, it is more likely the CatCon, EGR, or EGO sensor and/or A/F ratio.

#5 nathan.chase

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Posted 31 July 2006 - 10:15 PM

How far off were you on the NOx? Overheating might have some effect, but depending on what mode was tested/failed, it is more likely the CatCon, EGR, or EGO sensor and/or A/F ratio.


so it failed in the sustained driving field.by a few hundred. I don't hav ethe figures in front of me. by ego you mean o2 sensor? and with a computer driven model can I actually adjust the mixture?

thankx
-nate

#6 rallyruss

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Posted 31 July 2006 - 11:24 PM

Thanks for the help. I connected the fan motor directly to the battery and it worked. The connector for the fan is where I got a undouplicated voltage reading. I will test the voltage at the themoswitch in the radiator. it has two lines coming out. Is one ground? I'll double check the radiator ground.

also do you think overheating would be a cause of NOx. I am not sure how much that can influence NOx.

thanks for the reply!


NOx is directly related to heat. overheating will definatly affect it.

by the way they are required to place a fan in front of the car during testing. If they do not it may fail for NOx. there was a local shop that was failing cars by not using the fan then charging 50$ to "fix" it. they would then retest it with the fan and it would pass.
you may also want to check the radiator. they tend to plug up on the inside and have the fins erode on the outside.

good luck.

#7 edrach

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Posted 31 July 2006 - 11:46 PM

Thanks for the help. I connected the fan motor directly to the battery and it worked. The connector for the fan is where I got a undouplicated voltage reading. I will test the voltage at the themoswitch in the radiator. it has two lines coming out. Is one ground? I'll double check the radiator ground.

also do you think overheating would be a cause of NOx. I am not sure how much that can influence NOx.

thanks for the reply!

If you have the two pin thermo switch on the rad, you don't need the ground wire on the radiator since one side of the switch is power and the other goes to ground. Switch closed, fan should run; open switch fan should be off.

#8 edrach

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Posted 31 July 2006 - 11:52 PM

Thanks for the help. I connected the fan motor directly to the battery and it worked.

One other thing, if the previous owner did some "creative" wiring in that area of the radiator, he might have reversed the wires to the fan in which case it will run backwards and force hot engine air forward and retard cooling air flow when driving. Odd symptoms, car would run fine when fan was off; as soon as it warmed up the fan would start and then the car would overheat when moving and cool down when stopped. I've only seen one case of this, but it's easy to mis-wire the fan. Reversing the wires on the thermo switch will not cause this; the switch doesn't care which way the electrons flow.

#9 P K

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Posted 31 July 2006 - 11:55 PM

If your CO was okay, then I thought high NOx was directly related to a failing catalytic converter. I know I had to replace one Y-pipe with cat and the numbers went so waaayyyy down. My $0.02, good luck. r/ PK

#10 daeron

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Posted 01 August 2006 - 12:04 AM

the quick fix is to make a jumper wire to replace your thermoswitch with. This will have your electric fan running whenever the key is on.this shouldn't pose any electrical difficulties, but if you still arent getting good clean 12 volts at the fan plug after jumping the plug for the thermoswitch, then there are more problems.

edit
about a year after I got my first car, gov. jeb bush abolished the emissions testing program in florida.. which had only ever been enacted in palm beach, broward (ft lauderdale) and miami-dade counties... so i had to pass in my geo to get the tag, then again the next year because i missed the cutoff day by like three weeks. then, no more. Now, I kinda feel guilty.. because i have never given much mind to the emissions my cars let out.. and as such, I cant provide any help at all with the emissions side of this thread.. but overheating is always bad. If you can jump a wire from one side of the thermoswitch plug to the other (this is the plug in the wiring harness of the car), then you will have simulated the thermoswitch saying "turn on." recheck for 12 volts at the fan plug then. i bet that you get it, because you got some voltage before, for a second.. and lost it forever. my two bits.

#11 nathan.chase

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Posted 01 August 2006 - 01:12 AM

Thanks so much for the help everyone. I have lost light to jump the thermoswitch so that will have to be tomorrow.

I am really hoping that the cooling problem will change the NOx problem as this would make things easy. Otherwise I might be in to computer diagnostics. I haven't used these ECU's/ECM's before, do you need a special tool or is it just some connector that needs to be jumped to start the code reading and such?

THanks for all the help

Pay it forward
-nathan

#12 daeron

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Posted 01 August 2006 - 02:28 AM

i cant give you the breakdown on the procedure by heart, but it has been covered in the last 3 or 4 pages of posts in the forum, and it is in the USRM. There is a plug in the engine bay, or under the steering wheel, that you connect and then you read a flashing light for codes. the codes are all in the forum in threads, as well as in the USRM. there are two test modes, one of them displays codes that have caused check engine lights since the last time the memory was cleared (ie battery unhooked for >1-10? second, or cleared the right way after repairing the issue) the other test mode (as i understand it) is a general purpose diagnostic run over the FI componentry.. and there may be issues in all that which could cause overheating, but you could also have some sort of leak somewhere that is causing you to lose coolant, or failing to maintain pressure... if the radiator cap is open it doesnt work, right? if it doesnt operate at a higher pressure than atmosphere the the water boils and turns to steam, which doesnt cool as well as water. nowehere near. im having some overheating problems myself, so i am currently pretty well versed in this aspect of the motor... :- ) you might also want to look into a product called SeaFoam. It comes in a metal bottle in better auto parts stores, but its getting very popular finally. it is a petroleum distillate solution designed to soak into and dissolve all the crud built up throughout the entire cylinder head and vacuum system. it cleans injectors, valves, fuel rails, you name it.. it seeps pretty much everywhere. to use it you (well, read the directions, but in brief) pour a small amount into a cup, remove the vacuum line going to the brake booster, put a thumb on it, start the car, suck up the juice with the vacuum line, let it run for ~30 seconds, shut it off for like ten minutes, cut it on and drive around kinda hot for a little while.. or free rev it in your parking lot, but there will be ALOT of smoke and i mean a COPIOUS amount because all that crap just burns off...... and then you run mucho cleaner. you might also want to try a trick that my dad used to get our 4bbl 5.8l OHV ford van thru emissions several times.. go to the hardware store and buy denatured alcohol.. burn your fuel tank mostly dry, and pour half a gallon of that in.. go for a quick spin before the check to get it good and flushed, and see how she goes. NOTE.. the denatured alcohol thing is a trick i know has been used many times without negative results... but im not sure its kosher with fuel injection seals, etc. I know the issue with burning alcohol as a fuel in american vehicles is predominantly one of the wrong blends of rubber, and i do not know if this might cause harm to your engine... but i dont think so. any opinions on that? not as a long term thing, just to get thru emissions?

one time we did that, among a few other things (rebuilt carb, manifold gaskets, radiator, tranny flush) and the thing was almost the cleanest vehicle theyd seen that month!! it was a GREAT feeling, panicking on the way in, hoping wed pass, and getting this virtually zero emissions report!! i dont remember what was scheduled, but the limits were lax in south florida compared to cali, im sure. anyhow, some more thoughts.

#13 nathan.chase

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Posted 05 August 2006 - 03:05 AM

Dear all,
THank you for your suggestions. I toyed around the thermoswitch and fan trying to diagnos the problem and I eventually did. I stipped the wires before the standard harness for the two prong thermoswitch. I checked for voltage and hot plenty. in the switch nothing so I cleaned up the switch. Once i got voltage in the switch and ran the car till it was over the half to see if the switch would come on. Nothing. At this point I assumed the switch was getting power but not working as the fan was not opperative. I jumped the thermoswitch to see if all the wiring from the there on to the fan was working and the fan kicked right in. I replace the switch and refilled the radiator which took some burping. I now am going to try and run her hot tomorrow to verify the fan operation. I have a temp dial that is similar to the gas and oil pressure gage. spans about 120 degrees. At mid way I assume the fan should come on right? Also does anyone know what the dipstic in a manual trani is for? what kind of oil it take as mine is below low mark. Is this the gear oil?

thanks and let the subaru's rock! I am falling in love with mine.
-nate

#14 rallyruss

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Posted 05 August 2006 - 10:47 AM

Dear all,
THank you for your suggestions. I toyed around the thermoswitch and fan trying to diagnos the problem and I eventually did. I stipped the wires before the standard harness for the two prong thermoswitch. I checked for voltage and hot plenty. in the switch nothing so I cleaned up the switch. Once i got voltage in the switch and ran the car till it was over the half to see if the switch would come on. Nothing. At this point I assumed the switch was getting power but not working as the fan was not opperative. I jumped the thermoswitch to see if all the wiring from the there on to the fan was working and the fan kicked right in. I replace the switch and refilled the radiator which took some burping. I now am going to try and run her hot tomorrow to verify the fan operation. I have a temp dial that is similar to the gas and oil pressure gage. spans about 120 degrees. At mid way I assume the fan should come on right? Also does anyone know what the dipstic in a manual trani is for? what kind of oil it take as mine is below low mark. Is this the gear oil?

thanks and let the subaru's rock! I am falling in love with mine.
-nate


sounds like you are on the right path.

the trans dip stick is to check the tranny fluid level (and its the filler hole). use good quality GL5 gear oil.

#15 daeron

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Posted 06 August 2006 - 08:08 AM

i dont know when the thermoswitch turns the fan on, but i know i was testing two different units.. one i never confirmed a failure on because i "failed" both originally.. and it took a full rolling boil of hot water to turn the "good" switch on, so it wants at least 200+ degrees F. I have a digidash so my gauge isnt anything like yours anyhow, but i am unaware of any problem with simply ignoring the thermoswitch. AGAIN, anyone who wants to chime in with a problem with the idea of hardwiring past the thermoswitch, PLEASE feel free as i am ABOUT to do this but have not yet... the fan has been hardwired on anyhow because my brother never checked the thermoswitch, and hes the mechanic.

#16 skishop69

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Posted 06 August 2006 - 11:36 PM

NoX emissions are caused by one thing only... Excessive combustion temps. This however may be caused by several things. The three biggest offenders are... Too much timing advance, causes excessive cylinder pressure which in turn creates too much heat during combustion. Poor cooling system. Pretty much self explanatory. High compression combined with too little timing retard at mid to high revs. Same explanation as too much timing.

On vehicles prior to OBD II (up to '95) the CAT has nothing to do with NoX. There are a few exceptions to the rule though. Subaru is NOT one of them. There are other causes, bt heat and timing are the most common. Replacing your CAT will not affect your NoX reading. Start with the basics.

#17 NorthWet

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Posted 06 August 2006 - 11:44 PM

...On vehicles prior to OBD II (up to '95) the CAT has nothing to do with NoX. There are a few exceptions to the rule though. Subaru is NOT one of them. There are other causes, bt heat and timing are the most common. Replacing your CAT will not affect your NoX reading. Start with the basics.

Old Gen Subarus use separate reduction and oxidation cats. The frontmost, IIRC, is the reduction cat that would perform the reduction reaction on the NOx.

#18 skishop69

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Posted 07 August 2006 - 10:51 AM

I'll have to look into that. I remember that back in the 80's, only California CATs had to be NoX reducing. Since most of the cars I smog are OBD II, I think some of my old school info may be foggy.:confused:

#19 gbrand

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Posted 07 August 2006 - 09:16 PM

look at link in first post in this thread i posted in New Gen-gives good background on NOX vs CO and HC emissions..

http://www.ultimates...ead.php?t=41006

On my 80, the coolant sendor in the radiator went bad, and caused overheating as the fan would not come on until waaaaaaay to late. Once replaced was just fine, only noticed it if stuck in traffic, on hwy airflow enough to stay cool. . Never got around to installing an overide switch for "just in case".

Let us know how it works out




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