Failed smog test due to OBD-II - thermostat?

kenikh · 11:29 AM

I failed the OBD-II portion of my smog test here in Washington state (King County) due to what the computer said was:

Failure in the coolant recirculation
Oxygen sensor

The car is a '99 323iS (e36). The check engine light was on before I took it in. The tech seemed to think that if I replaced the thermostat, it would cure the problem. He said that the oxygen sensor sometimes shows a false failure if the thermostat is out of whack. I since bought the thermostat from Pelican, but am wondering if I should replace the oxygen sensor as well? My next test if free, but if it fails again, I have to pay. It's less the money than the hour out of my work day to get this done.

Has anyone had a similar experience?

BTW, the manual says to use a special tool to remove the fan to get at the thermostat housing and to drain the coolant while at it. Are there any special tool workarounds for the fan tool? Also, the coolant in my car is fresh. Is there any real reason to flush it?

kenikh · 02-28-2005, 07:32 PM

bump

jamin325i · 03-01-2005, 04:16 AM

no reason to change coolant, only topup and bleed after thermostat change with your regular 50/50 mix coolant.
have not you noticed an erratic temp gauge? it should go vertical and stay there within about 5 minutes after starting if thermostat is good.
as far o2 sensors, have they exceeded or near their recommended mileage limits? as i understand it, the '98 has 4 so its gets expensive, unless only 1 has crapped at an early life mileage. so a diagnostic test may be involved to find the bad one.

in my area you only need to have no obc2 check engine lights on to pass emmissions. no sniffer is needed in your tailpipe. so, if your light goes away with new thermostat- if indeed it is needed- than you should pass your next inspection. if this happens, you have no need to then confront the o2 sensor issue.

kenikh · 03-01-2005, 06:58 AM

Yes, the temp needle was erratic. My guess is that the thermsotat is stuck open as it takes forever to come up to temp.

The 4 oxygen sensors were the main reason I was hesitatnt to swap them out. They aren't cheap either. I'll swap the thermostat this weekend and cross my fingers that the light goes out. I would assume it will go out, although I hear ocassionally you need a reset switch to do it.

One more thing: the factory manual says I need this set of tools to secure and remove the fan:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2493861103

Is the job easy to do without them or should I just bite the bullet and buy them?

jamin325i · 03-01-2005, 01:17 PM

damn, i lost my thread i just typed.
anyhow, your link said about $58 for the 3 tools. seems high as some say a tool is available at bike shops and you don't need 2. my '95 used a 32mm.
i only had to use the 32mm thin wrench and a rubber mallet to slap it to loosen viscous fan. the nut is reverse threaded to normal. others have tips on holding the viscous fan and may turn up on a search.
as always look at orientation of old thermostat and if new one has an arrow or hole orient it upward.
you should not need to remove the radiator itself.
as always, bleeding a bmw coolant system of air is a challenge the first time but well worth learning as this is most trouble prone system on car.
on mine, disconnecting the battery cable a few minutes should allow a clearing of codes. as always have your radio code known before disconnecting battery.
on mine, when restarting from a disconnected battery may cause ragged running for a few minutes as computer re-learns settings.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

The beauty of the OBD cars--the Check Engine Light (CEL) will tell you if the problem has been cleared or not. So replace the t-stat, bleed the coolant system and such, and clear the codes. Then drive around for a while (several days, I would think!) and see if the CEL comes on. If not, stop in for your inspection. If it comes back on, replace the O2 sensor. Or have the codes read again and see what they are.

--DD

kenikh · 03-25-2005, 10:52 AM

I finally got around to pulling the thermostat and installing the new one this morning. It wasn't too difficult once I figured out the fan removal. I don't think there is any doubt that the thermostat was the culprit now:

It was a bear to get out since the thermsostat was totally deformed inside the housing. Nothin a set of vice grips didn't fix!

I'll go grab some more coolant today and reinstall the battery. Hopefully everything works!

Thanks again to all of you for the help.