T-Stat Failure?
 

The temp. gauge never reaches the mid-point and stays cold. Now its been super cold here in CT (contributing to my CCV failure. See other post) but it seems odd even at highway speeds it never gets there. Matter of fact when I get on the highway the temperature gauge gets colder closer to the 1/4 mark.

Obvious T-Stat failure in the M54?

Sounds like it is stuck open.

Any codes (not check engine lights, but fault codes)? That might give you a good indication.

I didn't have any scans done.

I read in an E39 post that there could be air in the cooling system?

Could be air. Bleeding with the nose higher than the tail helps get the air out of the system.

Many auto parts stores will read the codes for free (they want to sell you stuff). Autozone does. Don't know what stores you have there in the People's Republic of CT, but see if you have a stored code for low coolant temp.

Do the M54's have the electronic thermostats like the N62's? Mine threw a code and a CEL on my trip back to Vegas from DC. Fortunately, it wasn't stuck closed (or open), but rather partially stuck open; enough so we could easily drive home in December with no problems.

T-stat is open.

The t-stat should be closed until the engine warms up, then it cycles open and closed to maintain the engine temp within a narrow range. Your t-stat is stuck open and the engine never gets warmed up.

It appears in at least one thread in the on-line community that I can get away with NOT draining all the coolant to accomplish this as a DIY. Just take out the cover underneath the engine and capture what will come out of the hose/t-stat with a tray/bucket. Any comments on how much coolant is lost in this DIY?

How hot should it run when fully warmed up?

If the coolant is clean, you can capture what comes out and put it back in. If the coolant is not clean, then it does not matter what comes out, you have to replace it all. In the 3 Series cars, this engine takes 11 or 12 quarts -- 3 gallons.

You want a 50/50 mix of coolant and water, but it's not rocket science so you can be off quite a bit without creating any problems.

While the t-stat is out, you can run your garden hose through the engine until it runs clear, then if you refill with 5 or 6 quarts then top off with water, you will be at the magical 50%.

You can buy 50/50 premix, but strangely it costs more than a gallon of straight coolant.

Another strategy is to drain what you can, then add a gallon of straight coolant so that you have an empty bottle, then use another full bottle to make your own 50/50 premix, then top the system with that. (This method prevents you from flushing the block with your garden hose.)

To drain the system, you can open the petcock on the bottom of the radiator. I like to disconnect the lower hose at the radiator and get the coolant out of the top half of the engine -- when you open the t-stat, this will drain anyway, so you may as well control the mess.

It should be something in the range of 90 degrees C, which is somewhere around 200F. The needle should point straight up. A needle width or two to either side of straight up is okay, if the needle is at the 1/4 mark the engine is cold, and if at the 3/4 mark, it is hot.

Why?

Buy distilled water at the grocery store. Use it for flushing and mixing with fresh coolant. Avoid using tap water (or mineral water, etc). This REALLY reduces mineral deposits in your engine.

I have 3/4 of a container of BMW 50/50 on hand. I was trying to understand how much coolant would pour out when I disconnected the hoses to the t-stat. I'm thinking I can do this without a full drain but rather a top off/bleed after the t-stat replacement. The coolant in my X was flushed less than 2 years ago.

While I haven't done a forum search to see if your question has been answered in an earlier thread, I don't recall reading a thread that addresses your question. I suggest you try it and measure the amount needed to refill the cooling system. I would be interested in the answer.

Based on the location of the thermostat, my guess it won't be enough to matter. It would be easier and not make a mess to drain the system and capture the coolant if you want to use it again.

It's ok to reuse the coolant if you collect it into a clean container. Drain the radiator from the bottom drain plug which will get about a gallon out. When you remove the hose at the thermostat, have your catch pan or bottles ready as the engine/valley pan ( on a V8) will drain out there - another 1/2 to 3/4 gallon.

If I am reusing coolant (knowing that it was new, etc), I pour it through a large cone coffee filter placed in a large funnel to catch any scale or other junk that may have fallen in there. If it's really new as you say, it should be clear blue fluid you could inspect in a bucket.

+1.

Your coolant should be clean and suitable to be captured and used over again. Top as needed with the premix that you already have.

I haven't done this on an X, but on my E46, I did it standing in the driveway in January. I don't recall it being enough coolant to make a huge difference or even mess. Heck, I'm not even sure I removed the electric fan (XI manual), when I did it. I replaced the T-Stat, then bled it in through the overflow tank. Remember to respect the overflow tank and not fill it to the top, but to where the shoulder of the tank curves up to the lid.

I replaced the t-stat and did my belts while I was in there this afternoon. Quite a bit of coolant came out in the process. I'm guessing about 2 pints as a point of reference. Unfortunately I may have gotten some coolant and/or water I used to rinse the spilled coolant in electrical component(s). Car wouldn't turn over. Finally did after a few tries. Went in the house for about 20 minutes and gave it another shot. Same result. Got it started and took it for a 20 minute ride on the highway to assist in the drying process. Hopefully no issues tomorrow.

Getting something wet should not be a problem, else nobody could drive in the rain, or after leaving the car wash.

The main electrical item on the front of the engine, and near the job site, is the alternator, and it has no trouble being wet.

X started and ran perfectly today. Great sense of satisfaction on this DIY. I was quoted $593 for the T-Stat replacement by my local dealer. My Indy is tracking 30-40% less on average.

If you were working on your car and had doors open, or key on, or whatever, then you likely drained the battery if the No Start issue was that it was cranking slowly or not at all. If this is the case, you would do well to plug in your battery charger over night.

Nope..none of that was the case.....but again...everything appears to be working fine now.

Wait a minute...Im not afraid to admit a bone head move every now and then...the rear hatch might of been open for 2 hours....perhaps that drained the battery...oops.