Thermostat Stuck Open? Please Advise If There's Anything Else I Should Check

[Gimpdiggity]

Hello everyone. This is going to be a bit long as I'm going to explain what I have had done, and what I have tested/observed. I will also mention right off the bat that I've read about as many threads as I can on the subject, and I'm just asking to try to help put my mind at ease as I'm the type that gets kind of consumed by these types of things. So, thanks in advance for staying with me here.


Recently purchased a 2005 330Ci. Took it for a comprehensive inspection after purchase and it came back pretty good. The shop specializes in BMWs and other European cars, and has a lot of good reviews on FB, Google, etc. It needs some of the things that any 13 year old car needs...the hood lift supports could stand to be replaced, the rear shocks will need to be done soon, things like that.

I had them pay particular attention to the cooling system as I know it's the Achilles heel on the car. They told me it looks like most of it had been replaced sometime since the car was new, and according to the Carfax there was a service of the cooling system about 10,000 miles ago. That said, it was low on coolant...not sure exactly how much as I did not fill it myself, I just mentioned that it was a bit low. They found a bit of evidence of a leak at the temperature sensor, and recommended replacing that. I went ahead and did that, and as such they replaced all of the coolant. I must also mention that they did pressure test the system and said there were no signs of obvious leaks, and the reason they recommended changing that sensor was because there was evidence of a leak there...so I'm guessing some dried coolant or something? I asked if anything else might need to be changed, and they said that everything seemed good to go, and mentioned that the thermostat wasn't throwing any codes.

Anyway, after picking the car up today in about 29 degree weather, I noticed on the drive home that it was VERY slow to warm up. It's only a 6 mile drive from the shop to my house, but it is about a 15 minute drive. By the time I got home the needle on the dash was only really at about the first white line, just outside of the blue. Certainly not in the middle of the gauge.

So I started reading. And reading. And reading. To the point where my wife told me I needed to chill out.

The shop had mentioned that after driving the car for a bit, it would be prudent to check the coolant level again as there may have been a bit of air. They DID bleed it, but as I've found by reading everything I can, it seems that sometimes a bleed needs to be done a few times to make sure that all the air is out. So, when I got home from work, roughly 13 hours after I picked the car up, I took a look and sure enough the coolant was low. I followed the DIY I found online for bleeding:
Key in position two but car not on with car level
Heat on 91, center vent on three red dots
Fan on low
Expansion tank cap off
Bleeder screw out
Poured in 50/50 BMW blue and distilled water until it came out of the bleeder screw, and no air bubbles were present

It took about a cup of the mixture, and there were only a couple of bubbles. I then siphoned the "extra" out with a baster, and got it to the point where it's right between min and max.

I started the car and let it run for a few minutes, per the DIY I found, and the temperature crept up a bit...but it was slow. After a few minutes I took off for a little drive. I was getting some heat from the vents, but it certainly wasn't what I would call "hot," and the car seemed to very slowly creep up in temperature.

Finally, after a good 25 minutes or so of just kind of tooling around the neighborhood, I FINALLY had the needle in the center of the gauge. At this time, when driving at a decent city speed, 35-40 MPH, I would get VERY hot air out of the vents...like enough that it was making me a bit uncomfortable.

So I came back home and decided to give the OBC a try and look at the temperature of the coolant. So I did the trick to get it unlocked or whatever, and what I found seemed very low.

When idling in the garage, the temperature was reading 69-70. So I took it for a drive, and when I'd get up to about 45 MPH or so, it would dip all the way down to about 60, then creep back up as I drove more slowly. I didn't have time to take it out on the highway, but I'm guessing it would have dropped even more.

I got home and shut it all down, tired of messing around for the evening...and the wife wasn't too happy as I'd pretty much missed dinner.

So after she went to bed I went out and checked it all out again. The coolant is the exact same level as it was after I topped it off this evening. I checked the fan clutch on the front of the engine by trying to stop it with a rolled up magazine with the car idling and it easily stopped the blades.

After all of this, I believe that I have a faulty thermostat that is stuck in the open position.

I think I can narrow out the heater valve as I get heat pretty good once the car is finally up to temperature.
I think I can narrow out the fan clutch as it stopped when I touched it lightly with the magazine.
I have no major leaks as the coolant level was the same as it was before I started driving around.

So, that leaves me with a stuck thermostat. The only thing I question is why it's not throwing a code? I have read that it's not particularly uncommon for the thermostat to not code.

I guess what I'm asking after all of this is this: Is there anything else that I should be checking/having checked to diagnose and repair this issue?

Thanks.
Jeff

[dhurley34]

Replace the thermostat. If it was replaced 10k ago with substandard parts, then its a common failure.

[Gimpdiggity]

Let me try this again...I tried editing my previous thread and it...deleted the whole message? Okay, here goes again:

Hi everyone. I know that these types of threads are asked and answered, and I have read a whole bunch of threads about it, but I'm hoping to put my mind a bit at ease as I'm the type of person that kind of obsesses over these things. This will be a bit long, but I wanted to mention the things I've had done already, and the things I've observed/checked on my own to make it that much more clear what I'm experiencing.

I recently bought a 2005 330Ci. I took the car to a shop in town that specializes in imports, BMWs and Mercedes it seems in particular, that has stellar reviews on Facebook, Google, etc to have an inspection done. I asked them to pay particular attention to the cooling system as I've learned that it is in fact the Achilles heel on the car. Inspection came back pretty darn good...it needs a few things that any 13 year old car needs...new hood lift supports, new rear shocks in short order, it's missing a jack pad...things like that. They told me that most of the components on the cooling system look as if they've been replaced since new, and on the Carfax it does have listed a coolant system maintenance record about 10,000 miles ago. They said that the car seems as if it was pretty meticulously maintained. That said, when I took the car in it was slightly low on coolant. I'm not sure how much as I didn't fill it up seeing as I was going to have it inspected and I wanted them to have it without me potentially putting any bandaids on it. They pressure tested the system and found no obvious leaks, however they did find evidence of a leak at the temperature sensor, so they advised I replace that. I'm guessing there was some dried coolant or something back there that they noticed. They mentioned that there were only some voltage codes, which I assume was from when I changed the battery the other day to make sure I had a good solid one in there.

So anyway, I had the car in for service to have that sensor replaced and new coolant put it, and picked it up this morning, in about 29 degree weather. On the 5.9 mile, roughly 15 minute ride home, I noticed that the car took a LOOONG time to get warmed up. Like, it was barely at the first white line when I got it home after that drive. The heat was blowing slightly warm, but nothing I would call hot at all.

So I let it sit, and started reading...and reading...and reading...to the point where my wife told me I needed to chill out. So from a lot of reading, I knew a few things to look into. The shop also told me that after driving the car for a bit it's possible it may need to be bled again to get any remaining air out of the system, which I have read is fairly accurate when it comes to these cars.

So when I got home I checked the coolant, and sure enough it was a bit low. I followed a DIY I found on bleeding as I figured I could give that a go myself. I did as follows:
Car on level ground, key in position 2
Temperature set to 91, fan on low
Unscrewed expansion tank cap
Unscrewed bleed screw
Poured 50/50 mix of BMW blue and distilled water until it flowed from the bleeder hole with no air bubbles
Bleeder screw back in
ET cap back on

It took about one cup of the mixture, and then I siphoned out the extra with a baster to get it to read right between min and max.

I then sat in the car and let it run, per the DIY, until it started to heat up a bit. I then drove the car around the neighborhood and my general area at speeds up to maybe about 50MPH. What I found was that the heat would blow warm, but still not hot, but the car did SLOWLY creep up to the point where the needle was in the center of the gauge. It took about 30 minutes to get to that point. Once it got to the center, though, the heat was blowing pretty hot...hot enough that I needed to turn it down a bit. I then got into the OBC and checked the temperatures. When at idle it was right about 69 degrees. At about 45 MPH it would dip all the way down to 60. I didn't take it on the highway as I was already probably in trouble for missing dinner with the wife, so I took it home and parked it.

A few hours later I went back outside to check a few more things. First, the coolant is at the exact same level it was when I first filled it this evening. I know it's a bit warm so it may end up being a bit low when I check tomorrow night, but there's no obvious leak as it's still pretty much the same. I checked the fan clutch by rolling up a magazine and using it to stop the blades, and they stopped easily, then started again when I removed the magazine. I then went back out for another drive with the OBC on temperature and found that at highway speeds it can dip down to about 58 degrees.

So, from all of this, I think I have been able to rule out a few things:
1. I don't think it can be a heater valve as I'm getting heat from the heater, and once it actually has warmed up to the middle of the gauge the heat is very warm.
2. I don't think it can be a fan clutch as the fan stopped when I used the magazine, which is what I've read is a fairly easy way to test if it's working right.

So this leads me to believe that I have a thermostat that is stuck in the open position, so it's not allowing the coolant to get heated up to the correct operating temperature. What throws me is that it wasn't giving any codes for that...but I've read that it's not exactly uncommon to have a thermostat NOT throw a code.

I guess after all of this, what I'm wanting to ask is this: Is there anything else I should check/have checked to help diagnose and repair this issue? This car won't be driven in the cold very much, I got it for a fun car not a daily driver, but there may be times when heat is a necessity...and I've read that an engine running too cold can cause decreased performance and poor gas mileage.

Thank you for sticking with me through this, and sorry that I had to post it twice.

Thanks.
Jeff

[Gimpdiggity]

Replace the thermostat. If it was replaced 10k ago with substandard parts, then its a common failure.

dhurley34, thank you. Can you see my post?

I went to try to edit it, and then it disappeared so I can't see it any more. I had a bunch of stuff posted but I can no longer see it.

[rbelton]

I've had several Wahler thermostats fail early with low miles within a year. Quality control just isn't what it used to be, probably not made in Germany anymore.

[shogun]

dhurley34, thank you. Can you see my post?I went to try to edit it, and then it disappeared so I can't see it any more. I had a bunch of stuff posted but I can no longer see it.

as you have less than 10 posts, a mod has to manually approve these posts (spam-o-matic forum software), takes a while. Anyway, I now merged your 2 threads to one, after you have 10 posts, you will see your posts immy

[Gimpdiggity]

as you have less than 10 posts, a mod has to manually approve these posts (spam-o-matic forum software), takes a while. Anyway, I now merged your 2 threads to one, after you have 10 posts, you will see your posts immy

Excellent, thanks shogun. I was pretty confused for a moment there.

[91e34M5]

You're overthinking the problem. You have correctly analyzed the lack of adequate heat, double checked coolant levels, read the OBC temps, so as you suspect, basically the only thing it could be is a faulty thermostat, a relatively simple fix.

[charter21p5]

Use a genuine BMW thermostat.


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[Eaglesail]

Thermostats fail...fortunately when they do... they fail open. If they failed closed, the world would have a big problem! Open thermostats (gone unnoticed) and introduce many engine issues if not known. If it takes more than 15 minutes of engine running time...say from 15 degrees fahrenheit...and there is only minimal heat coming from your heating system...you mat have a common issue emanating from a faulty or old engine block thermostat.

[Gimpdiggity]

My mechanic agreed with my assessment after driving the car and will be putting a new thermostat in tomorrow.

I would like to do this myself, but with 20 degree weather and no real place to do it, I’ll let the pros handle it.

Thanks for the input everyone.