BMW Blog

Ok, I was driving home from school one day and the check engine light comes on. The light came on when I reached the off ramp, stopped at a red light. I smelt some burning and I knew it wasn't good, so I made it home (which was only two blocks away from the off ramp) and parked the car with the engine idling. Suddenly there was a loud "pop" and steam came from under the hood :eek: . I quickly shut off the car and opened the hood. The steam cleared and aside from the mess, the only thing I saw was the upper radiator hose detached from the radiator with a piece of the radiator still in the hose. My temperature gauge in the car has never worked since I bought the car. I did the stomp test to get the engine code, 1223 - coolant temp. sensor. What could have caused the radiator to pop? I changed the antifreeze two weeks ago by myself. Can anyone tell what happened and how to fix it next time? Does anyone know of a good place to buy radiators? Thanks in advance! My car is a 1991 525i with M50 engine.

Did u bleed the system good? Perhaps there was air in the system and it overheated. Thats the only thing I can really think off.

any after market radiator would probably be as good as oem, if they claim oem quality. Otherwise I've had great luck with parts from the wreckyard.

I got a radioator from a 97 328i for around 100bucks.

If you get a rad from a newer car you should not worry about it blowing up on you anytime soon. maybe a radiator from a newer year model 5.
While your at it might aswell replace the rubber necks as well, they are known to go dry and break unexpectedly.

My bet is you didn't bleed all of the air out, or didn't bleed it at all...

Actually I tried to bleed the system following the procedure found on www.bmwe34.net but bleeding the system is still a mystery to me. Basically what I did was drain the old fluid with the drain plug, fill up the tank almost to the top, started the engine and let it idle, unscrewed the bleeder screw, and kept pouring new fluid into the tank until it maintained normal level. Then, I just screwed the cap and bleeder screw back in and drove. After driving, I would turn off the engine and check the level in the tank. If it was low I would pour new fluid in. I always had a premixed 50/50 in the trunk. Is this proper bleeding? I never had to bleed the system in my Accord or Miata. Also, before changing the fluid I put in Prestone's neglected system radiator cleaner fluid. I bought a new thermostat a month ago, but never put that in.... doh, maybe it would have helped. >.<

Thanks to everyone for the advice. Radiators are expensive, around $250 for my 525i. A question for Blazin95Red325i, what's a rubber neck? Is that a fancy term for a gasket that goes inside the hose? Sorry, I'm new to BMW and the forums if you couldn't tell already.
Thanks again!

I bled the system again today and drove my car around. After about a mile the check engine light turns on and I immediately pull over and shut off the engine. Same engine code, 1223. I can't figure out what is wrong. Is it me or the car? If there is another forum that can help me, please tell me because I haven't found the answer yet.

Maybe your coolant temperature sensor is bad?

Did you turn on the heater/fan fully while bleeding?
You have to eliminate the air in the heater core.

Did yu also drain the block? To do a coolant change that should be done.
When you put in the new radiator, you must drain the entire system if you are going to do it right.

I read up the FAQ on www.understeer.com and it says, "If your current coolant is blue or green, then do NOT use the pink/red/orange coolant. The two types do not play well together and will combine to form a thick sludge that is almost impossible to get out of your engine."

.... oops. Well, the coolant has not totally turned into sludge yet, and I'll make perfectly sure to change the coolant CORRECTLY this time and bleed it again CORRECTLY.

Before that I will install the new thermostat and get the temp gauge working.

Btw I'm still using the old radiator since it's not completely broken. There is still enough plastic left to slide on the upper radiator hose. There was some plastic in the way but I chiseled them off. Is this a good idea?

I hope nobody will make the same mistake(s) I did. Two last questions. What is a rubber neck? Are they expensive?

NEVER use pink coolant.

For more info, go on www.google.com and do a search for "dexcool class action lawsuit"

'Nuff said

Several comments. First of all, over time and heat cycles, the plastic parts on the BMW radiators become brittle and are prone to cracking. If your radiator has already cracked, then trying to keep using it is just asking for trouble - you may not have damaged your engine this time, but when the little bit of remaining plastic crumbles under the upper radiator hose, you may not be as fortunate.

That's also a reason not to buy a used radiator from the junkyard. The upper hose fitting on the BMW plastic-tanked radiators is notorious for cracking between 60-100K miles. Since you really don't know the history of the junkyard radiator, you really don't know how much time you have left on it - it may already be brittle, and start to crack when you install it. So, it's pretty much false economy. Especially if you drive an E36, since you can get a brand new OE radiator from somewhere like Zygmunt for a hundred-fifty bucks.

If your engine is throwing a temp sensor code, have you checked/replaced the temp sensor? Engine could be running hot because of this bad sensor - unfortunately, you can't tell because you don't have a working temp gauge...

Driving around without a working temp gauge doesn't really seem like a wise thing to do, since BMW motors seem to be fairly susceptible to damage from overheating.

Jim

Oh man, I didn't know changing antifreeze would be so complicated. I thought all antifreeze were the same! In fact, when I walked into the auto store I just picked a few gallons of antifreeze that was closest to the door, which unfortunately turned out to be the orange stuff. Now I know, that stuff is nasty!!

My radiator has the following numbers.
BMW
1723527
1719108
21.677.
01452

I'm wondering if it is the original stock radiator. Can anyone find out?
I'll be working on the thermostat, sensor, and coolant now that I have some time on my hands. I'll find a new radiator, but in the meantime i'll be using the old one.

Sounds like you overfilled it or didn't bleed it properly.
It is hard to overheat BMWs, but once the cooling system loses pressure/fluid, it is easy to wreck the engine.

edit: do not check coolant after driving, it won't be in the expansion tank. check it when it is cold to get the proper indication of what's in the system

Sounds like you overfilled it or didn't bleed it properly.
It is hard to overheat BMWs, but once the cooling system loses pressure/fluid, it is easy to wreck the engine.

edit: do not check coolant after driving, it won't be in the expansion tank. check it when it is cold to get the proper indication of what's in the system
What should I expect to see in the system? I replaced the thermostat with an 80 degree C, so coolant starts flowing sooner. I think I've bled the car to death. No matter how long I run the engine I get steam and spurts of coolant coming out of the bleeder screw plus all the coolant spills out of the expansion tank. I also tried bleeding the coolant through the screw with the cap closed, but the heater never blows hot when the car is warmed up and at idle.

As a note from a previous GM owner, talking to other GM owners, I have heard that if your engine has ever had green stuff in it you can never run dex (pink) in it, because it WILL turn to sludge eventually. Seems like staying green is safest.

I haven't driven the car more than 2 miles in the past week, keeping to the local roads only. Today I will try fixing the temp gauge. I am going to change the water pump this Friday and see if that will fix my problem. I ordered a GEBA metal impeller pump. I have read that the older plastic ones degenerate and fail. That is the only reason I have for coolant not properly flowing through my radiator if at all. With the car cooled down, nothing comes out of the bleeder valve. With the car warmed up, steam comes out.