I'm no expert, but recently had a similar issue due to replacement thermostat getting stuck shut. Did you replace the temp sensor in the lower radiator hose? What brand thermostat did you use in the refresh, BMW, Behr, Wahler, MTC, or some other brand? Some possible causes:
--Air pockets in cooling system
--New thermostat stuck shut
--Fan switch (temp sensor) in lower radiator hose is bad
--Aux fan relay failed, so can't turn on electric fan when it's hot

If you only overheat when you're not stopped but are fine when the car is moving, I'd guess fan switch (temp sensor) or relay problem. If your car reaches operating temp and the upper radiator hose is hot but lower radiator hose and radiator are cool, could be new thermostat is getting stuck shut. In any case you should be sure you bled the system correctly. How did you bleed the air out?

 

Did you properly bleed the cooling system?

 

you say you keep having to add coolant. are you leaking coolant? There are several small hoses around the engine and throttle. fill up the radiator and resevoir, take it for a drive, the park it and look for drips or leaks.

that's what happened to a z3 I had for a while.

gl.

 

If you don't properly bleed the cooling system, it will overheat, due to trapped air in the system. See this thread: http://www.e46fanatics.com/forum/showthread.php?t=689618

 

+1; if you're getting coolant coming out of your ET cap you have pressure building up which means you have air in the system which is forcing it's way up through your ET cap. Completely bleed the system with the heat and fan on full, key in the second position and pour coolant into the system until you begin to see fluid without bubbles. Just my two and a half cents worth...

 

hi dudes

im having this same problem with my 330 ci, it overheated on the way back from cornwall last week due to the belt that drives the water pump etc snapping. i have replaced the expansion tank as this was damadged by the belt. after replaceing the tank the car runs fine for a while then gets real hot.

do you think this is an air lock in the system.

cheers dudes

rich

 

It's amazing that not a day goes by for this forum without a similar thread. If you just done work on the cooling system and the car runs hot in 90% of times it is going to be a result of a bad bleed. It's clear that bleeding E46s is like black art. All I can recommend is to read the other 500 threads on this and eventually get the air out of the system.

 

Like everyone said before me , bleed your coolant .

Sent from my HERO200 using Bimmer App

 

Help! Pls...

If somebody can explain to me . I have BMW 320i e46 made in 2001(automatic trans) 4 valves per cylinder. PLEASE , if somebody can explain if electric fan comes between grill and radiator or not? Because , right now there is a mechanical fan between radiator and engine . This mechanical fan is connected to the engine and i understand that there is a different cooling fan position for automatic gearshift und manual gearshift . PLEASE if possible provide me with pictures of correct position of the electric fan on BMW 320i e46 made in 2001(automatic trans) 4 valves per cylinder. Is it true that this fan goes between radiator und grill and not between radiator und engine . THANK YOU .

 

In most E46 cars, if you have a manual, there is only one fan, an electric fan between radiator and engine. In most automatics, there are two fans, a mechanical fan attached to the water pump (with viscous clutch) and an electric fan in front of the radiator, between the A/C condenser and kidney grilles. Not sure if this applies to the 320i.

If somebody can explain to me . I have BMW 320i e46 made in 2001(automatic trans) 4 valves per cylinder. PLEASE , if somebody can explain if electric fan comes between grill and radiator or not? Because , right now there is a mechanical fan between radiator and engine . This mechanical fan is connected to the engine and i understand that there is a different cooling fan position for automatic gearshift und manual gearshift . PLEASE if possible provide me with pictures of correct position of the electric fan on BMW 320i e46 made in 2001(automatic trans) 4 valves per cylinder. Is it true that this fan goes between radiator und grill and not between radiator und engine . THANK YOU .

 

The cooling system on the E46 is a fairly complicated combination of a high pressure plumbing system and an electrical/electronic control system.

Getting the cooling system working right after a number of years of use is a rite of passage for the E46 owner.

Get this wrong and your engine is ruined.

Get it right and you have more years of reliable driving enjoyment.

It took me three trips to the dealer who sold me the car and always serviced it before getting the cooling system working reliably after an over-heating episode that ended in a flatbed ride to the shop.

My cooling system blew due to an intermittent failure in the electric/electronic radiator fan on the manual-shift sedan.

 

If somebody can explain to me . I have BMW 320i e46 made in 2001(automatic trans) 4 valves per cylinder. PLEASE , if somebody can explain if electric fan comes between grill and radiator or not?

According to realoem, yours is structured like other e46's. You should have a water pump-mounted mechanical fan between the radiator and engine. With your automatic, you should also have a fan between the radiator and bumper. If you open the hood and look in the kidney holes, you should see your electric fan. So, in summary, you should have both a mechanical fan as well as an electric fan. Weasel footnote: Some production doesn't exactly follow that, even though that's what the parts catalog says.

 

Thanx . I was confused , especially since i saw that the cooling is different with manual and auto gearbox . Thank you again .

 

replaced fan relay and still overheating..... whattttttttttt

 

Are you still getting coolant coming out of the expansion tank cap? :facepalm:

 

Cribs: standard cooling lecture...walk on by!


+1 read cooling threads until you bleed (literally, guys. You actually need to study the threads until there's at least a tiny drop of blood forcing its way out of someplace on your body...and it doesn't count if you slice yourself to get the blood and end the pain).

I've written a couple of times of bleeding...if you find a post of mine that's shorter and sounds like I'm a little annoyed, that's the one you should read. Mkodama and others here (Costco!) have great advice for you...but they forgot about the blood part.

Bimmersgarage...great guy, has vids on cooling (none with naked women yet!)--diagnosis and repair.

If you need to start the car when cool, rev to 4000 rpm for 30 secs. Open cap, add coolant, repeat as necessary.

But, don't assume bleeding...as in, don't head out on a long trip until you've got this sorted.

That this occured 1 or 2 hours into a trip makes me think more about the 'end of the trip' Getting off the highway, consistent speeds, heating up, fan maybe not working fully.

Could be bleeding, and easy to eliminate that, but monitor well and don't assume coz bleeding is our favorite, that it's your issue.

Also, you may have a slow leak, even if bleeding 'cures' the overheating...and it might happen again in a week or two. So, be wary, and don't assume.

Worry enough about it to monitor level of coolant...look for leaks by removing undershield. Rinse stuff off to id source of leak...and if it pertains and you can afford it...replace what you haven't replaced at some point, if you can't otherwise find a source, but still have the issue.

Someone replaced his ran relay, by itself...not with the fan. This is second time I've heard of someone doing this, so as probable suspect ebay part (right?), keep eye on that. I know I've mentioned this relay as I'd heard of it, but prior to a month ago, I don't this this relay was available. Hmmm? I haven't checked realoem for that, but legend was, you had to replace fan.

Sorry...too much, I know!

 

ok, i replaced the fan, waterpump and belts...stilllll overheating...system is bled properly each time!!!! WTF

 

I'm not sure if you answered the question about whether your therm was OE or an aftermarket one.

I hate to suggest throwing more parts at it, and would suggest bleeding again...maybe differently...as bleeding is something few here seem to be able to do.

Failing that, consider an AM therm as having failed. Either get a new one, or for grins...and a little extra work, you could remove the therm from inside the therm housing and see if that fixes the issue. If it does, you need a new therm. If it doesn't sorry!

Don't run without therm as you'll get crappy mileage!

...and, failing all that, at some point, know your limits and find a good indy. You can't drive while overheating, unless you want to have to buy a new engine or at least, put in a head gasket, maybe head.

Also, be patient. The car isn't messing with you...it's just a thing and something is obviously wrong. Patience is an important skill set to get things right!

Of course, I'm guessing...but hth!

 

What brand thermostat did you put in--Behr, Wahler, Genuine BMW, MTC, or....? When you first overheat, is the upper radiator hose hot and the lower radiator hose and radiator cool? If your thermostat is stuck closed, your belt isn't on, or the water pump has broken, then you won't have coolant flow through the radiator. If the water pump is working but the thermostat is stuck closed, you'll have coolant flowing through the expansion tank and upper radiator hose, but not flowing through the lower radiator hose or radiator.

Also when the car starts to overheat, does the electric fan come on?

 

yeup, the fan comes on, the waterpump is new with metal propeller...the t stat is bmw oem. tommorow i am going to check the radiator to see if there is a clog, thats the last thing i havent checked or replaced...if thats fine then i have no clue, the upper hose is hot and lwer is cool when it overheats but tstat is opening and fans are comming on!!!!!!

 

Iif upper hose is hot and lower hose and radiator are cool when it overheats, then coolant is NOT circulating through the radiator, and I can only think of a few things that could be causing that:

• New thermostat is defective and stuck closed. This happened to me, though not with an OEM BMW thermostat.
• Coolant temp sensor is defective so it sends gauge into red even though you're not really overheating (if steam and coolant are spurting out of ET cap, never mind this one)
• Radiator is clogged, like you said.
• New water pump already failed. Or you forgot to hook up the accessory drive belt.
• You just aren't bleeding it right. Bleeding it 5 times the wrong way is not any better than bleeding it one time the wrong way. Though most people do a better job the 2nd (or 5th) time than they did the 1st time (I did).
• Your car has been cursed. Remember that car you dinged in the mall parking lot but you didn't leave a note for the other driver? The other driver has magical powers and put a curse on your car.

Good that the fan comes on, but it won't help if no coolant is circulating through the radiator. How do you know the T-stat is opening? One tip on bleeding... after bleeding and closing bleed screw, if you lower coolant level to the proper level, do NOT open the bleed screw again to test if more coolant comes out. I suspect that if you've lowered the coolant from full ET down to proper level, opening the bleed screw again lets air IN to the upper radiator hose.

yeup, the fan comes on, the waterpump is new with metal propeller...the t stat is bmw oem. tommorow i am going to check the radiator to see if there is a clog, thats the last thing i havent checked or replaced...if thats fine then i have no clue, the upper hose is hot and lwer is cool when it overheats but tstat is opening and fans are comming on!!!!!!

 

help!!! radiator is fine...

 

This may have already been covered but have you replaced the temperature sensor in the lower radiator hose. Just my two and a half cents worth...

 

yup thats been replaced

 

When you go out to your car before you start it up and you open the expansion tank cap does the float stick rise to the top?

 

yea, i have bled and bled and bled and bled and then bled again!!! im getting extremely frustrated!!!!!

 

Five bleedings? Was the level changing at all...you need to add coolant each time?

Did you rev up to 4-5000K for 30 secs., open it up, and check level?

We're sort of running out of things...so a shop might be in your future.

You only bled five times, so maybe it's the sixth or seventh that's the charm...

Squeeze upper hose/burp, while car is running.

Miles (MK) is good with e-bleeding.

Then you go to pulleys/belts for WP...I don't think the water valve can be blocked, but maybe it's closed. I've heard of one guy banging it to get it open...low odds...but that's what you're down too.

Also, you want to tell us how you've been bleeding?

 

im going to just take the radiator out tommorow and flush it...i wasnt feeling good today so i didnt mess with it. what about a clogged heater core? could that be the culprit?

 

Heater core... I don't know but suspect not. A clogged heater core will prevent coolant from circulating through the heater hoses, but I think most of the time (in hot weather) the heater valve is closed and the car doesn't overheat. This assumes closed heater valve has same effect as clogged heater core. If you want to test heater core, try this, but do NOT let temp gauge go into the red.

1. Remove fan so you can safely feel lower radiator hose and radiator
2. Turn key to On while holding trip reset, to unlock test function. Enable hidden OBC function to monitor coolant temp.
3. Put vent dial to 3 blue dots; heater to 68F; fan off (opposite of bleeding settings) to let engine heat up faster
4. Start engine. Let temp gauge rise to middle and OBC temp rise to 90C, which should open thermostat.
5. Turn vent dial to 3 red dots; fan to HIGH; temp to 91F; this should open heater valve and turn heater into mini radiator
6. If temp rises >95C or temp gauge touches red, turn off car immediately and leave hood open.
7. Heat should be blasting out of the vents and the OBC temp should stop rising and stabilize between 86C and 95C because heater core is acting like small radiator. Temp gauge should stop at or near middle.
8. Turn off motor and remove key. Go feel upper rad hose, lower rad hose, and radiator. Verify that upper rad hose is hot while radiator and lower rad hose are both cool (which means thermostat or radiator circulation problem). Be warned that upper radiator hose may be hot enough to burn you.

If turning heat and fan on high does not control coolant temp, or air blowing into car is not hot when you're at 3 red dots and temp at 91F, then most likely your heater core is blocked or heater valve is bad. But this is also to verify that your radiator is not getting coolant once the engine is at operating temp. If lower radiator hose and radiator also burn your hand, that's bad for your hand but suggests your thermostat is opening and radiator is not clogged.

And how do you know the thermostat is opening?

 

head gasket...FML

 

Guys have done this. You up to it?

And, how is it you know this...not doubting you...just curious.

Sorry to hear the news, though. Went through this myself in e36, not doing the repair, just paying for it!'

How big of a leak is it...how much coolant you losing? And, if only gasket, not nearly as bad as an extra ?$ for head itself.

Start reading up.

 

yea im doing it myself, started yesterday....no collant was in oil or vice versa. Just allowing exhaust gasses in and building to much pressure in the system, thus coolant spewing from expansion tank...Im hoping the head is fine, odds are it is since there is no smoke from exhaust, or coolant in oil or oil in coolant...what you think?