Approximately 2 weeks ago, the neck on my radiator that the upper radiator hose attaches to, broke off. It was a mess. My engine couldn't hold any water, and it nearly overheated and burned up. Fortunately I was able to get it home, and pulled the radiator out the next day, and took it to a great radiator shop that did an outstanding job cleaning, recoring and painting it, as well as putting a new metal neck on it. The old one was plastic.
Last night, I was coming home on the freeway and started smelling that hot anti-freeze smell inside the car. Not good. I exited and pulled over, filling the radiator tank with water, and letting it cool down. As I drove away, when I accelerated, it made that rapid-fire knocking noise that it made when the radiator neck snapped off and there was no water in the engine. It sucked. I proceeded to stop at 4 more gas stations along the way home to let the engine cool down, and put a little more water in the radiator tank. it made that bad noise all the way home, and the engine would barely stay started when going in reverse. Thankfully I made it home safely. When I would fill the radiator tank up, it didn't really seem like it took all that much water, and yet, the engine was overheated big time, and it was almost as though it had no anti-freeze/water in it at all. There's a blockage somewhere. Someone mentioned that the thermostat my be stuck closed and not allowing water to get to the radiator/engine? Does that sound about right? It doesn't seem to really be leaking water much. I really need to get my car up and running. What does everyone here think?
Thanks.

Tom B.

Definitely check the Tstat.. I would just replace it...

Did you replace the radiator with a new one??? Or did they just quasi-fix the old one??

I would also suspect a water pump, its possible that it fried itself when you lost coolant.. its also possible that it wasnt circulating properly...

IF you didnt blow the head gasket I'd be pretty surprised, these motors do NOT like to be cooked like you did.. honestly, it was a mistake on your part to keep driving, you should have had it towed..

You can check the Tstat, take it out and drop it a pot of boiling water, you should be able to watch it open from fully closed, and then it will close when you take it out of the water..

Cooling systems should be easy to diagnose... Heres what I would do if it were my car..

1. Take out and inspect the Tstat, and just replace it (its like $10)
2. Make sure the radiator isnt blocked (Just run a hose through it, cant hurt to try)
3. Inspect/replace water pump.

Do you have any oil/water mix? pull the dipstick and see if the oil looks milky... do you get any white smoke out the tailpipe?

I think your engine is probably cooked. Be prepared for at least a head gasket. NEVER drive an overheating (let alone overheated) BMW engine. Aluminum does not like to be overheated, and tends to warp or crack. Worst case scenario you're looking for a cylinder head.

How they managed to put a metal neck on a plastic/aluminum radiator is beyond me, but it sounds like a hack. Get a proper replacement - either another plastic/aluminum one or a traditional copper/brass one if you prefer (I actually have one of each used for sale - PM me if you're interested). Replace the thermostat. Make sure you get the right one - check if you have the "A" housing or the older one - and make sure you mount it the right way around: both of these are important, as if the incorrect part is used or the stat is mounted backwards, it will not open fully. I would strongly suggest replacing the rest of the cooling system as well - at least the hoses and the water pump.

The radiator is a rebuild. They did an outstanding job. It's good as new. Thanks for the tips on the water pump and the head gasket. I'm putting a new gasket/thermostat in tomorrow morning. A mechanic friend of mine is going to check out the water pump, and do a check to see about the head gasket. He said if steam/smoke/water drip is coming out of the tail pipe, then it's blown. You guys got me a little concerned now. I think I saved it OK by stopping every 4 minutes on the way home to let the engine cool down and put more water in it. I'm hoping for the best. I'll know tomorrow. I'll keep you posted.
Thanks for all your good advice.
It's greatly appreciated, sir.

Tom B.



Definitely check the Tstat.. I would just replace it...

Did you replace the radiator with a new one??? Or did they just quasi-fix the old one??

I would also suspect a water pump, its possible that it fried itself when you lost coolant.. its also possible that it wasnt circulating properly...

IF you didnt blow the head gasket I'd be pretty surprised, these motors do NOT like to be cooked like you did.. honestly, it was a mistake on your part to keep driving, you should have had it towed..

You can check the Tstat, take it out and drop it a pot of boiling water, you should be able to watch it open from fully closed, and then it will close when you take it out of the water..

Cooling systems should be easy to diagnose... Heres what I would do if it were my car..

1. Take out and inspect the Tstat, and just replace it (its like $10)
2. Make sure the radiator isnt blocked (Just run a hose through it, cant hurt to try)
3. Inspect/replace water pump.

Do you have any oil/water mix? pull the dipstick and see if the oil looks milky... do you get any white smoke out the tailpipe?

Installing a new thermostat in the morning. I know not to drive it hot, but I absolutely could not leave my car in the horrible, crime ridden part of South LA I was in. It just wasn't an option. I was careful to stop every 4 mins to let it cool down, and put more water in. I hope you're wrong about it being cooked. A mechanic buddy is going to check out the water pump and check for head gasket damage after I finish up the thermostat install.
No, the oil is not milky. I checked.
Thank you for your outstanding reply and advice.
I will keep the post posted what happens.
Thanks again.

Tom B.

I think your engine is probably cooked. Be prepared for at least a head gasket. NEVER drive an overheating (let alone overheated) BMW engine. Aluminum does not like to be overheated, and tends to warp or crack. Worst case scenario you're looking for a cylinder head.

How they managed to put a metal neck on a plastic/aluminum radiator is beyond me, but it sounds like a hack. Get a proper replacement - either another plastic/aluminum one or a traditional copper/brass one if you prefer (I actually have one of each used for sale - PM me if you're interested). Replace the thermostat. Make sure you get the right one - check if you have the "A" housing or the older one - and make sure you mount it the right way around: both of these are important, as if the incorrect part is used or the stat is mounted backwards, it will not open fully. I would strongly suggest replacing the rest of the cooling system as well - at least the hoses and the water pump.

I hope I'm wrong about the engine as well. Maybe you were able to keep it cool enough to avoid damage.

The steam out the tailpipe and/or milky oil tests are OK; another check is to pull the spark plugs. If you find one or two that are particularly clean, you've found which cylinder or cylinders the head gasket is leaking into; the coolant basically steam-cleans the plugs as it evaporates. This test is better for diagnosing small leaks into the cylinders that may not show up clearly at the tailpipe.

I'm still somewhat skeptical of the radiator in terms of long-term reliability. Also check your expansion tank for leaks (usually around the bottom outlet) and pressure test the cap.

Hey. Thanks for all your good info. You'll be happy to hear that this story actually has a happy ending. With the new thermostat in there, it runs like a champ. I dodged a seriously large bullet. I realize that. Head gasket is fine, water pump is functioning properly, and no milky oil. Letting that engine cool down every 6 blocks, and continuously putting more water in the expansion tank was the key. I'll check the plugs if I have some time this week.
Thanks again.

Tom B.


I hope I'm wrong about the engine as well. Maybe you were able to keep it cool enough to avoid damage.

The steam out the tailpipe and/or milky oil tests are OK; another check is to pull the spark plugs. If you find one or two that are particularly clean, you've found which cylinder or cylinders the head gasket is leaking into; the coolant basically steam-cleans the plugs as it evaporates. This test is better for diagnosing small leaks into the cylinders that may not show up clearly at the tailpipe.

I'm still somewhat skeptical of the radiator in terms of long-term reliability. Also check your expansion tank for leaks (usually around the bottom outlet) and pressure test the cap.

Here's an addendum. After putting in the new thermostat, and putting on a new gasket with sealant, it was still leaking. It turns out the water pump was leaking. Found one for $33.00 from an auto parts wholesaler. Install today. Pick up tomorrow. This has GOT to be the final chapter of this.
Thanks again for all your valuable help.

Tom B.

Um, $10 bucks sez there's gonna be a part 2.
Been haere myself & it aint pretty, you'd shore no bout it if it was leaking about your water pump, would be spraying steam &/or hot water! My $10 sez you've cracked your head, sounds exactly like watt happened to me once upon a time.
Pretty easy for a mechanic to test the water for htdrocarbons or something, but Double or nothing, that water is leaking into your combustion chamber, will run okay with a leaking water pump.
Gonna cost you about $1500-2000, straighten & mill head, it will be warped, new head studs...
See if you can get a recon, but these mite be off of a coked motor 2!
happened to me M520, '86. now fixed, but moved overseas & left it behind, sitting in a container!!
Good luck

Well, I hope you're wrong. It appears to be fine now. Water was coming out of the breather hole on the water pump when it got hot. Between the new water pump and new thermostat, it all seems cool.

Um, $10 bucks sez there's gonna be a part 2.
Been haere myself & it aint pretty, you'd shore no bout it if it was leaking about your water pump, would be spraying steam &/or hot water! My $10 sez you've cracked your head, sounds exactly like watt happened to me once upon a time.
Pretty easy for a mechanic to test the water for htdrocarbons or something, but Double or nothing, that water is leaking into your combustion chamber, will run okay with a leaking water pump.
Gonna cost you about $1500-2000, straighten & mill head, it will be warped, new head studs...
See if you can get a recon, but these mite be off of a coked motor 2!
happened to me M520, '86. now fixed, but moved overseas & left it behind, sitting in a container!!
Good luck