92 325is Lambda Control C9 Code -OEM O2 replaced

[rdbrock]

Hi Guys,

This is my first post, so please easy on me .
I have 92 325is that I just replaced the O2 sensor (Bosch OEM ) and 300 miles in I got a C9 code where check engine light comes on for a few seconds and turns off immediately ( while on the expressway). Runs fine, Idles normal. Anyone have the same issue with this C9 Lambda control error?

Thanks!

[Manolito]

The quick answer is - if the light went back out, it is probably not serious, so you can keep driving and see if it happens again.

A '92 is OBD I so the system should adapt to a new O2 sensor fairly quickly. I would think it would be dialed in well before 300 miles, so it was probably not just a transient code due to internal adjustment.

All the system tells us with a C9 code is that the signal from the oxygen sensor was out of bounds for a few seconds. That could be caused by a defective connection to the oxygen sensor heater, or a leak in your intake ducting that is causing the mass airflow reading to be inaccurate, or a poor temperature sensor that is causing the fuel mix to be off, or any number of other things.

Another possible (though unlikely) suspect: I have been less confident in Bosch parts since the new owners moved a lot of the manufacturing to China and India. Did you happen to notice where this sensor was made?

[Jared at Pelican Parts]

I agree that it is likely a loose connection somewhere.

[rdbrock]

Thanks for the quick response guys. I did reset the engine code twice now, and both times came back. I have checked all the hoses and wiring and do not see any obvious loose connections, not sure about leaks. I may take the mass air flow apart to clean the sensor inside and see what happens and then reset code again. The O2 oxygen was made in Germany that I just replaced. Also, I was getting a 46 code prior this which was to replace the oxygen sensor, that code is now gone and did not come back after replacing 02 and now "Lambda Control" seems to be there , but the check engine light is off and from time to time comes on for a second and goes away so far and it rides strong and does not idle, the code is actually there when I scan it and never goes away unless i reset it.

[rdbrock]

Update: On my way home yesterday I noticed that the car was running hotter than normal, the gauge marked a notch passed the middle mark. Not to mention the heater stopped working recently and I did not notice , it blows air , but just cold air , and A.C works fine.
I guess I must have multiple issues ? For the overheating I don't know the last time it had a radiator flush, I'm thinking old fluid or possible bad thermostat and a possible heat valve that needs cleaning for the heater issue? Possible water pump all together? Which is the best way to rule out or a way to determine in steps what to to start looking to replace/do first?

My BMW is a 5spd and In regards the lambda control (C9), I paid closer attention, the light seems to actually light up for a second while I'm driving down a hill or flat while running in neutral gear and I soon as I put it back in gear light goes away.

Weird stuff.. What do you guys think?

Thanks!

[Manolito]

You almost certainly have two different issues here.

Sounds like you have air in the coolant. I presume that you have looked at the expansion tank and confirmed that your coolant level is normal? If so, pull out the thumb screw in the top of the radiator and top it off until bubbles stop coming out of the bleed screw. That should help with the engine temperature and heater, but only temporarily. Air that mysteriously appears in the cooling system means that there is a leak somewhere. If you are not seeing any evidence of coolant leaks, the most common leak is a crack inside the expansion tank that allows the radiator to suck in air rather than water as it cools.

As for the oxygen sensor light tripping on downhill grades or deceleration, if the car idles smoothly, then we can rule out vacuum leaks and leaking fuel injectors. That leaves me with an exhaust leak that is letting air in on deceleration, or a bad connection in the heater circuit on the oxygen sensor so the oxygen sensor gets too cool on deceleration. I once had an intermitant heater circuit on a Volvo that drove me nuts for a year until I finally ran a new wire all the way from the fuse box to the oxygen sensor plug. That finally fixed it.

[rdbrock]

Please help !!! For the heating issue: I can' t drive anywhere, I drained all coolant and cant fill it back up ( i think ) only because reservoir is still full?

Today I I drained the old coolant. I took out the plastic screw under radiator and let that flush out and then I went under the manifold ( block plug ) and let it drain completely and as well as took the plastic screw out of the reservoir expansion tank, and all the fluid seems to drain out except the fluid in the expansion tank ( reservoir ) , did not even move.... I got the bentley book and followed it , but the reservoir doesn’t drain, it’s still full with radiator screw open and block plug (under manifold) wide open and the reservoir still full with the bolt wide open as well, I don’t get that. I left it all screws over night and yet reservoir seems like it never was touched. What would trap fluid in the reservoir and not let it drain out?
I followed the manual to turn the key ign on to the heat on the passenger side several times and let the fan blow without turning on ign. I drained all the fluid out, and I don’t think I can fill it back up as something is blocking it as reservoir remains the same before the flush. I’m thinking this is in correlation of the heater not working. The car is fully drained of coolant so I cant drive it anywhere because there is no fluid other than the one stuck in reservoir that isn't going anywhere. Help!!!!! I can't drive it anywhere now that all coolant is drained.

[Manolito]

Relax.

The hose from the bottom of the expansion tank runs across the bottom of the fan shroud, then back to the block on the driver side. I think that you will find that there is a spot in that hose that is higher than the bottom of the expansion tank, so the expansion tank cannot gravity drain completely unless you blow the water out by pressurizing the expansion tank, or you could siphon it out with a small hose, or you could flush it out by adding distilled water clear to clear the last of the old coolant out of the tank.

If my theory that your expansion tank is crumbling inside is correct, you will regret having gone to all this work without replacing the expansion tank. Draining the coolant out of these cars is a messy PITA (but then, you already know that).

You should use BMW coolant and distilled water when you refill it. You can buy it on line cheaper than at the dealer. For now, you can run pure distilled water for a short while until you resolve your cooling system problems. When the problem is solved, drain out a gallon of water and add a gallon of coolant. Don't run pure water for an extended period because you need the corrosion inhibitors found in coolant. Do not use Dexcool (organic acid based) coolant. I once tried Preston 5/50 long life (organic acid based) coolant and it ate up a brand new Nissen radiator in only two years.

[rdbrock]

Hi Manolito,

Do you believe I have a defective radiator expansion tank?
I think I understand how to siphon the existing fluid, but how would you add existing distilled water or even any fluid if the expansion tank is blocked?
Is there a way to fill up your radiator bypassing the expansion tank on e36 (92 325is)?

I've got all the valves wide open, but expansion tank remains full and not going down, I can manage to remove the liquid in there, but to add new liquid seems to be the same place/issues ( thru expansion tank to add distilled water or colorant right? E36) .

I'm not following you when you say add fluid if the expansion tank when it's clogged up, could you please explain that?.
Do you believe the heater valve is clogged up and not letting any fluid down thru the expansion tank?
This is my theory , but I'm a newbie on owning a e36. What do you believe needs replacement?
I'm thinking heater valve, and expansion tank at this time, would you agree?

keep in mind the heater isn't working at the moment, it blows cold air right now, and just started to overheat a notch above normal thats why I went with the flush to see if it could solve the issue as from I was told the previous owner had not flushed fluid in a decent amount of time, but only to make it even worst perhaps in short term temporally ?

Thank You!!!

[Manolito]

I do think that your radiator expansion tank has most likely failed, but I don't think that the fact that it is not emptying is a serious problem. Have you tried pouring more water into it to see what happens? I suspect that if you pour water into it, the water will push out and the level will stay in about the same place. You can refill your system through the expansion tank.

Here is a picture that shows what I think you will find if you cut open your reservoir;
http://forums.pelicanparts.com/101-projects-discussion-forum-bmw-3-series-e30-e36-1982-2000/446171-bleeding-radiator-perhaps-problem.html


The physics here is similar to your toilet. It has a few inches of water in it, and although the drain is open, it does not empty. If you pour a gallon of water into your toilet, it will simply push some of the water out, and the level in the toilet will stay about the same.

Carrying my toilet analogy further, when your toilet empties momentarily during a flush, it is because a siphon is established during the flush. If you had not removed the bleeder screw from the top of the expansion tank before you opened the block drain, it should have siphoned the water out of the expansion tank. However, since the screw was out and the system could get air, the expansion tank did not 'flush'. If the expansion tank did not siphon empty with the bleed screw closed, then I would be quite sure that there was a crack inside the expansion tank that was letting air into the system.

Just pour some water into the expansion tank and see what happens. If my suspicions regarding your expansion tank are correct, you will fill the system and all will be well, but in a few days, there will be air in the system again and the car will start to run warm and the heater won't work again. Only way to find out is to try it and see.

[rdbrock]

Manolito, thank you, it worked just like you said. I got all the air out of the expansion tank, the heater even started working again, how ever the engine is still getting hot even with new fluid.
I almost thought I had it, but I think the problem now could be thermostat ?

[rdbrock]

I also noticed the top hose of the radiator is extremely hot, while the bottom hose is much cooler(you can even hold the hose without burning). While it's running real hot, the radiator fan never comes on, I looked at the connection,fuses and it's all good.
I'm thinking if it's a bad thermostat would it explain the reason why the bottom hose is much cooler than the top hose and that's why the radiator fan never comes on?

Thanks!

[Manolito]

Once again, it sounds like there are a couple of things going on. Twenty year-old cars can be more of a hobby than a mode of transportation, can't they?

The top radiator hose should be a lot hotter than the lower hose. That means that the radiator is cooling the water. However, you are right to suspect the thermostat. These cars are hard on thermostats for reasons that no one has ever figured out. However, usually if a thermostat fails, it fails to open at all so the car gets REALLY hot when you drive it.

If you replace the thermostat, replace its housing as well if your car uses a plastic housing. Those plastic housings shrink and warp with the years so they leak if you try to re-use them. You can replace it with an aluminum (aftermarket) housing if you choose. Put the old thermostat in a pot of boiling water. If it fails to open, you know that you found your problem.

If the car is hot enough to see the temperature gauge above the midpoint, the electric fan should come on low speed to try to help cool it. Turning on the A/C with the car running should also turn on the electric fan. There should be a temperature sensor in the passenger side end tank of the radiator. If you unplug the sensor, there should be three wires. I forgot which wire is common, but you cannot hurt anything, so short between the wires with a paperclip with the key in the 'Run" position. You should be able to get high and low fan speeds by shorting between the pins in that plug.

If you don't have the low speed fan, 90% of the time it is because the contacts are burnt in the relay. This is a cheap and easy fix. If you can hear the relay click but the fan does not come on, it is easy to figure out which relay it is (just touch them when it is clicking) but I think it is the one closest to the firewall.

Another thing that will cause an old e36 to run warm is that these cars came with water pumps with plastic impellers. On cars that rolled up relatively few miles, the impellers got to be about 15 years old before the water pump hit 150k miles and wore out. When those plastic impellers get to be about 15 years old, they crumble and stop pumping water effectively.

If you decide that you need to replace the water pump, there are several tips and tricks for that job, but there are probably instructions with pictures on this site.

If this feels a bit overwhelming and expensive, we all feel your pain. Today I pulled the alternator and power steering pump off my wife's '04 330i with 98k miles on it so I could replace the gasket between the oil filter housing and the block that has been leaking oil all over the place for a year. While in there, I noticed that her water pump has started seeping coolant. Grrrrrrrrr, at only 98k miles????? My experience with driving a pair of e36s a cumulative half-million miles tells me that I don't want to replace just the water pump on a 7 year old BMW. While I am in there, I will replace the water pump, thermostat and housing, the radiator, the expansion tank, misc plastic parts and O-rings, and every water hose that I touch. I had better start saving up because that water pump probably won't make it through the summer.

[rdbrock]

You're absolutely right, this is now my 2nd daily driver that I'm rotating around and I've had it less than a month and already doing work on it, It's got 137,xxx k and I'm hoping I get at least 250k-300k with proper care and regular maintenance.

My thermostat housing surprisingly is metal ( my guess this was their first e36 build in 92 so they used better parts?) and I suspect a metal impeller water pump in it too maybe? I won't know until I take it apart. I did not have a chance to check out the radiator fan yet, but I did remember hearing some clickings even before it overheated ( few weeks after owning it) I suspect that the relay is probably bad also.

I hear you on your 04 330i with 98k, you sound like me and trying to be proactive and replace everything you touch.
I'm going to go ahead and order a new water pump with metal impeller, thermostat, top and bottom radiator hose and thermostat hosing gasket, I was thinking to replacing some pulley(s) belt if I needed to. I think the expansion tank might be good, it drained well it is sealed tight when I bleed the air out. What would you recommend I go ahead and change while I have all fluid out ( for the 2nd time) and have the thermostat out? I'm trying to be pro-active and go ahead and replace everything I can while I'm in there.
Do you get your parts at a dealer? I've seen some OEM replacment parts for a fair price on ebay, what are your thoughts on this?

Thanks again for your assistance!

[Manolito]

If that is the original water pump at 137k miles and 20 years, it is due for replacement both for age and for miles. If it has been replaced in the last decade, it should be OK. If you are replacing the water pump, you will need to buy or make a tool to hold the water pump pulley while you loosen the fan clutch. You will also need a thin-jawed open-end wrench to turn the fan clutch nut. These tools are easy to make if you have a drill and a grinder. The fan clutch is left-handed thread.

When you pull off the top radiator hose, look inside the fitting on the radiator and see if the plastic is crumbling inside. This is the hottest spot on the radiator so this is where it crumbles and fails first. When if fails, the fitting will snap off the radiator with no warning and you will spray coolant everywhere. These radiators last about 8-10 years of normal use.

Someone likely replaced the plastic thermostat housing with an aluminum one before you bought the car.

Look hard at your heater hoses, particularly the one that is beneath the intake manifold, for age degradation. Replacing the heater hoses is a PITA that involves pulling the air plenum off the firewall. I stood straddle the engine and pulled for all I was worth, and nearly did a back flip over the radiator when that sucker finally broke free. You can replace the hose under the intake manifold if you have skinny arms and a stubby screwdriver and you remove the oil filter cover. Nasty job, but better than being stranded in the outback on a summer day.

Examine the fan clutch for oil leaks or rattles. If you replace the fan clutch, you probably want a new plastic fan. It is 20 years old and getting quite brittle by now. You don't want a blade snapping off at 6000 RPM and putting a bump in your hood.

I have four 3-series cars ranging from 98k to 285k miles. All look and run great, but I buy a lot of parts. I am blessed to live only four miles from an excellent BMW dealer, but I buy 95% of my parts on line. I can't mention any suppliers other than Pelican (which is a perfectly good supplier) because the forum will delete the name of any competitor that I post. It is, after all, their forum, right? These days, there are lots of excellent vendors on line, and I cannot think of any bad ones that have not been forced out of the business.

[rdbrock]

The previous owner had it over 4 years, but drove less than 10K while he owned it. There a nice list of service records, but I don't see any on the water pump and thermostat/radiator. I also agree with you as it looks like the metal thermostat hosing was put in later because looking at the radiator it doesn't look that old and I also noticed that the radiator shroud bottom piece is out of place and the fan blade has chipped edges.
Either someone didn't connect it properly or it popped out of place (perhaps when the blade hit it ). I think I will have to replace the heater hoses, I think you are referring to the heater valve is it? ( has 3 hoses going into close to the firewall), I think I read an article about those (heater valve )clogging up and needing to be rinsed - that may explain why I have no heat? If the thermostat was indeed bad, the heater would not work either correct? Or would the heat work normal with a bad thermostat? I used to have a 82 Datsun 280zx and if I recall correctly I did have to replace a thermostat on it once and I don't remember the heat working at all - but I can't really compare right? I'm sure an 82 Japanese engine would be very different from a 92 German engine (with so many electronics /air/ sensors).

Thanks for listing the tools and tricks here, I'm going to need it. I will start getting things together and I will work on it this weekend again.
My cousin also has a 97 328i that I'm actually driving right now for him to see what is going on with it, he is having at least 4-5 codes popping up on it that I read using the peak tool. I was going to ask you after I look the codes up and see if you could give me some input, you are very knowledgeable on your 3 series cars. Do you think I should post it here or create another thread?
I'll come back to this thread to work on this lambda control issue after I get all of this overheat and heat not working situation fixed and let everyone know what I did to fix it.
Thanks for your advices, I will follow them.

[Manolito]

Definitely start a new thread for the '97 or this will get confusing.

Generally the lack of heat is the result of air in the cooling system, but I also recall a post from someone who had no heat and found his heater control valve to be full of rubber crumbs from failing hoses. If you find that, you should back-flush the heater core because it will likely have trash in it as well. Just figure out which way the water flows from the heater control valve to the heater core, and while you have the hoses off, force water through it the other direction.

[rdbrock]

I started a new thread for the overheating issue , can you believe the parts I changed were 20 years old?, I replaced original water pump that was 20 years old. I did not remove the Thermostat housing since it was Aluminum and also still original (bmw logo inside housing), but no damage around the seal. I replaced hoses,water pump, these wore all original to be since 1992 and it still had ever worked on since for 20 years exactly and 137K still have original window sticker.

[rdbrock]

I think I have air in the bleeding system, but I could only replace around 8 Liters of coolant and yet fully drained..