ok heres the story so about 4 years ago i get my 535i motor rebuilt pretty much decked and milled everything, the reason why--it overheated. my dad brings it home says it was overheating again on the way home. but would get hot and then the needle would drop back to cold so we through it in the garage and left it. 4 years later :buttrock we bring the beast out. and im ready to try and fix it. so i start with the thing that most people would... the thrmostat. so i take it out, put it in boilin water and it opens so that wasnt it. and just to make sure i ran the car with the thrmo out and it DID overheat again. ok so the thermo is not it. now what about the radiator, well took the hoses off and blew through it all ok. now the only thing left are a few things. one being the water pump which i just replaced about 3 days ago. not it again. so now im gettin to the point of lookin for anything. :dunno . so its one of two things it could be that there is a clog in the heater core( when it just started to overheated i turned the heat on full blast and the air was forsty cold.) or the box by the drivers side front window is cloged. not for sure what it is but its the only thing that the hoses run to that im not aware of what it is. so there it is sorry for the long discription but ive been waitin 4 years and im so close ... i think...
thanks for the help

Moving this to 5-series forum. No idea what the box on the driver's side is ....

It may be easier than you think.

If the heater was cold there was air in the system.

To bleed there is a screw on the thermostat housing.
With the engine at normal temperature to get the thermostat open, heat to maximum, and the engine at 1000 rpm, open the screw until the coolant is solid and no air.

Now there can be two issues causing this overheat.

The impeller on the water pump, but if it got cool after the temperature as the electric fan kicked on, I would suggest the fan clutch.

To test the fan clutch, with the engine cold you can stop the fan with a rolled up news paper. With the engine warm the clutch will not let the fan be stopped.

The fan clutch is a CCW 32 mm nut, requires a thin 32 mm wrench turn backwards. That is 1 1/4 inch for you cold beer drinkers.

Bicycle shops carry a thin 32mm crank wrench, use a hammer to loosen, by tapping on the end of the wrench.

Later,

Originally posted by XOC
No idea what the box on the driver's side is ....

It's the heater valve (basically an electric solenoid that opens to allow water to the heater core).

Ron Carter covered most of it.But,if the car sat 4 years,you need to reverse-flush the cooling system to get the crud out as well.And hope the head gasket isn't the next problem.Has the head been re-torqued properly every 15K?
Another solution is to rewire the A/C fan in the front of the car,with a dash switch that can turn it on anytime,to add cooling power even when air is off.Worked for me on two other cars.

Bob G./rags535
BMWCCA#5217

ok thanks for the help, this is what i have done so far
i unhooked the hose going from the the tank and heater core to the other side of the thremo housing and bypassed the heater core with the other hose hooked to it (catch that? what i did was bypass the heater core.) and once again started it up and in about 3 mins it was hot... so i shut it off, now the fan that is on mine is not electronic it is driven off the water pump i havent tried the news paper idea yet but im going to... here in a little bit when it gets cool ill back flush the system. i was almost positive that the heater core was going to be the problem but it wasnt so the only other thing i can think it could be is a clog in the block or a bad fan clutch or im going to the extent of sayin that a certified BMW technican put the wrong head gasket on (possible?)
anyways thats where im at the input is great thanks and any ideas would help
thanks again

The hardest car known to mechanicdom is a 6 cyl BMW. Bleading the damn thing takes more skill than most have! Make sure the thermostat is in correctly - the radiator cap is new, and the motor is filled through the upper hose as much as possible. Loosen the bleader screw on the t-housing and let it idle until you get AF flow :clap: Now! run it until it just starts to creap past 1/2 to 3/4 on the gage. Turn it off. wait about 5 minutes then crack the bleeder and see if it steams. Probably will so when the steam quits then fill radiator and see if it goes past 3/4 again. Pretty much repeat this until you have AF at the bleader imediatly.

The heater probably has air rtapped - not clogged. Turn heat on during this. No heat tells me it packed with air!
Hell of a thing if it wasn't blead 4 years ago - and that all!!
one other is that the head gasket was correct and the possages matched up - go with step one first!!

Mark Goodson
:buttrock

ok here is the latest... i looked at some bills that were in the dash and pretty much everything except pistons, rods and and crank was replaced including the water pump(wish i would have found them earlier) anyways i started to bleed the system like mark said and about after an hour or so i got heat. today i started at it again and got it to idle and stay in the middle mark with the heater off for about ten mins... it would have done it all day too :redspot so i decided to take it for a drive to see what would happen so i got about 3/4 mile and it started to climb really slow but kept goin. so what i did was turn the heat on and it was really hot obviously it got about to the 3/4 on the gauge until it stopped movingot it back to the garage and let it sit for awhile and bleed the steam squizzed some tubes and everything but its like i cant get the little last bit. does it normally take this long?
could someone tell me if im on the right track or not?
thanks so much
cant friggin believe that it was just a bleedin problem for 4 years .. to bad the mechanic didnt take the time to do it right, or my dad have the common sense to take it back and say it was overheatin owell
thanks again

I think you're on the right track. The M30 is notoriously hard to get bled all the way. Mine went pretty well, pretty quickly, but I didn't have the system opened up, so probably not much air in it.

I read this in an old archive and it worked well for me:

1 - Disconnect the line that runs from the radiator back to the expansion tank somewhere near the TANK end. Hook the end of the line on something high up so that the line is by far the highest point in the cooling system

2 - With the end of the line in the air, gently blow into the expansion tank to 'pressurize' the system. You should hear air bubbles and 'gurgling' from the line you disconnected. After a while, the gurgling should stop. Reconnect the line, start the car, and look for a steady trickle of coolant coming from that line into the expansion tank. That should mean you're pretty close to done.

Your getting there - After it cools over night top it off with the bleeder loose. You should get it to run out without running the motor at this point. If not go ahead and run it until it bleeds AF. run the Heater during all of this and provided the radiator is clean inside (corosion from sitting) it should get going!!

Mark

It totally sounds like a bleeding problem. Another way to bleed the system is to fill the system as far as possible, squeeze the upper radiator hose to pressurize the system, release the bleed screw to let out pressurized air, close the bleed screw and release the pressure on the upper hose. Repeat until coolant only comes out. This avoids heating parts with some of the other suggested approaches - let it get hot from running, then bleeding.

Another point: next time you have the thermostat out, drill a small hole in the outer perimeter, 1/8" or so, and when you reinstall it, orient the hole to the top of the engine. This will let you bleed *much* faster. Such a small hole will not interfer with the action of the thermostat.

Just some thoughts,

if the head gasket was wrong, it would leak wouldnt it, therefore water would mix with oil and cause a think white creme in the block. check under the oil cap and if there is no white creme, then its not that.

This may sound stupid but my friend had the same issue. how did we solve it....Parked the car on the slant of his drive way. The anfle Forced the air pockets out.........Hope that ....that makes sense....


theDogger

Head gaskets have steam holes throughout the water passages to control how much water passes into certian areas. The wrong gasket wouldnt necessaraly leak but would provide inefiecient water supply to areas

Fixed yet? :D

well i figured out the problem, all these years the thing hasnt been bled right! bastards... didnt take the time to do it right and now im stuck tryin to bleed the damn thing. its ridiculous ive opend that bleeder valve qiute a few times and still havent got it yet... so far ive got it bled to the point where i can run the car with the heater off and the car idling and the car will stay right in the middle now if i put it in gear it goes up to the 3/4 mark in about 5 mins or so. i can still after i shut it off hear bubbles in hte upper hose when i squiz it. ivew even lifted the car up about 2 feet in the front so all the air would go to the front(dont know if that helped. now what im goiun to do is get plates for it and then drive till its hot get out and bleed it and so on, sound good ? any other advice?

thanks for everything guys!

If you are bleeding it by opening the bleed screw after it is pressured up, that should do it, after a time or two. You should be done shortly.

Then just drive it and enjoy it!

ok well i took it out for a drive and this is what i got to..

it runs 3/4 on the temp gauge with the heat on
with the heat of it will get hot, so when it got hot i shut it off got, out with the key on ignition not the motor on. i heard a noise unfimiliar... ended up being the motor that runs in to the heater valve... its making a buzzin noise ( not right? ) sure doesnt seem like it should be makin that sound... about this time the hood comes slamin down from a gust of wind OUCH! :complain didnt get any blood on the interior though. after i got cleaned up went back out motor was equally cool figured the heater valve motor wasnt goin to be makin any noise cause it was kool now... i was wrong same thing? could this be a problem clogin a passage ? o also the bottom radiator hose is still alot cooler than the upper and if im correct i think they should be almost the same. and trust me theres a big difference. once you guys reply about the heater motor i may end up replacin that and if that doesnt do it ... its goin to the mechs and again to get bled im gettin sick of it! any one want to try???
thanks

535power:

The buzz you are getting is not fatal, and even if your heater hoses were completely plugged, they could not cause the engine to overheat. So let's try some remote-control diagnostics:

1) What level is the coolant in the reserviour?
2) When the guage is at 3/4, are the radiator hoses hard?
3) Do they stay hard for 10 - 15 minutes after you shut down?
4) The radiator hoses should *not* be the same temp - the input should be much hotter than the output. Can you keep your hand on the input (lower)? If all is normal, it should be too hot to keep your hand on, but not hot enough for you to pull back instantly.
5) Are you losing coolant?
6) Do you have any condensation (white, gummy stuff) on the inside of the oil filler cap, or on the dipstick?
7) Does the temp guage stay at 3/4 if you are rolling at highway speed?

Answers to these will help - but I am still suspicious of the head job - any chance you could get a leak-down test?

Good luck!

I will repeat the issue is most likely the fan clutch.

Later,

ok about the fan clutch it was replaced with the rest of the internals 4 years ago pretty much all the guts

reservior tank is full
hoses are hard at 3/4
they do stay hard after 10-15 mins
yes the bottom heater hose is hot but hot enough to keep my hand on

im only losin coolant when i bleed it thrugh the bleeder valve
no gummy stuff on the oil cap
stays at 3/4 when rollin at highway sppeds but will go down alittle when i stop (weird?)

head job was done with the rest of the work 4 years ago

also what does the buzz mean?
that motor goin out?
thanks for the help again

The fan clutch doesn't scan from my point of view - that would fit symptoms of overheating at idle when it is sitting. I don't think 535power is doing this in a hot climate (!). I'm also kind of suspicious of the radiator, although 535power said he ran water through it.

I'm still thinking head gasket, which would be confirmed (or denied) by a leakdown test.

Later,

hey man i got lost thru many days since I have read the top of the thread, anywho, I would try running without the thermostat in place. just cuz it open once in the pot doesn't mean it opens in the motor. top hot bottom cold is a symptom of the thermo is not opening. also are you getting hot air thruogh the vents? when you squeeze the bottom hose, does water come out of the top? if yes your radiator is good and if not your rad is bad. trust me I just fixed this problem on a car I bought from a guy that the $stealer told him he had a blown gasket. After replacing thermostat and bleeding the system for 1 hr. I have now drove it 300 miles and idled with A/C on for 2 hours without over heating. damn it if you can't inderstand anything I am saying I will re-type it again tomorrow. its 03:21 am right now.

ok, i just read my last post, i dont even understand what i was saying. lets try this again.


1. Check for flow in radiator. (squeeze your bottom hose with the rad cap off. You should immediatly get spillage at the top.

2. you mentioned the temp came back down when you stopped and idled? check your water pump. it may not be up to par. Guys dont you agree that if temp comes back down then its not a head gasket?!?! Idling is most worst (heat wise) than driving.

3. Check your fan.

4. what mixture are you using.

5. Remember those parts that were replaced 4 years ago could have gone bad too.

6. pull that thermostat. ( just to take out a varible)

7. Bleed bleed bleed bleed. just dont forget to refill

fan is fine
mixture is correct
water pump has just been replaced
pulled the thermostat when i did the heater core bypass same thing still overheated
been bleeding for ever about 3 or 4 days now 2 hours at a time

also when i said i checked the radiator all i did was blow air throught it but what was goin in also came out.

im kinda in awww right now that this is so hard to figure out i mean reallestically does the thing need to be bleed to the smallest degree to run properly

and i stil thing that is the problem cause when i started to bleed it... it got better and better till now

there is one thing that i could think of is that when i had the thermo out the system was obviously not bleed right so if it is the that could be it.?... idont know any opioions?

thanks again for the help guys i appreciate every thing and you guys stickin with me thanks :)

535power:

If you can go back and pass along the answers to the 7 questions in my earlier post, I can give you lots better help.

:wave:

in answer to larry F.

1. reservior tank is full
2. hoses are hard at 3/4
3. they do stay hard after 10-15 mins
4. yes the bottom heater hose is hot but hot enough to keep my hand on

5. im only losin coolant when i bleed it thrugh the bleeder valve
6. no gummy stuff on the oil cap
7. stays at 3/4 when rollin at highway sppeds but will go down alittle when i stop (weird?)

thats whats still goin on
this is what i have thought of now trry to follow me on this:
ok water is sucked into the top of the pump from an elbow which goes to the other side of the thermostat housing ( you may have to go look at yours?) ok right next to that elbow is the top radiator hose. on the oppsite side of those hoses is where the main outlet for the coolin of the block is (correct?) so what keeps the radiator fluid from goin in to the elbow and never getting to the upper radiator hose to be cooled? thats a good question. now i have looked in there where the two hoses come out of that housing and there is no divider its all open. now unless there is a different way that the fluid flows could this a potiental problem if there was something that was supose to be there and it just didnt get there after the rebuild?

i know its a long shot and its probly somthing else but im out on the limb now.

im pretty sure i got the thing bleed all the way unless the raditor is full of air cause ya cant squeez it...lol
thanks for the help fellas
:95

Bleeding is not THAT hard on the M30B34 or M30B35. If you are still getting steam out of the bleeder nipple with no thermostat and regardless of the heater open/closed, then

You have a cracked head or blown/poorly sealed head gasket!

Sorry, dude, but I'd bet money the head got cracked when it was overheated years ago OR the new head gasket didn't seal. You did do the 3-stage torque, right? Something like 20lb-ft, then 40lb-ft, then start and run the engine until hot, then retorque to 35 degrees angle torque. You do not need to touch the head bolts ever again. You can even reuse them.

It's not the radiator, it's not the thermostat, it's not the heater core trapping air, it's not the phase of the moon. You have a cracked head.

Get the system pressure checked and see. You can rent the tool from Autozone or buy it (Stant brand and others available) for about $50 to $80.

535power:

I'm afraid your answer to 7) places you right where James does: bad head or head gasket. Who knows if the original head job was done badly or whatever.

I am inclined to recommend you have a leakdown test done - this puts a metered 100 psi of air pressure into each cylinder at top dead center (both valves closed) and measures how fast the metered air escapes. As a plus, you can listen for where you hear the air coming out to determine which part of your system is shot. In your case, if you leave the coolant tank cap off, you are likely to see coolant pushed up and outta there. Personally, I have my doubts that a coolant system test, at about 15 psi, would show up your problem. Save the $50 buying that tester and pay a professional (NOT the guys who rebuilt it before!) to do a full-up leakdown test.

Sorry about the bad news. :az:

well same opinion from 2 people ouch... well i got a buddy thats got a leak down tester..thats what we were goin to do in the first place but decided to try the thermo and then everything else first...
owell its just money right?!?:dunno

anyways thanks for all the help guys sure as hell couldnt have done it with out and also thanks for stickin with me this whole time i know after awhile people get burnt out on a non solvable problem. by the way how did you come to the conclusion that the head gasket or head is broke? just curious

thanks again

You can get a coolant system pressure tester to check whether the coolant system leaks or not.

I say head gasket or cracked head because I've seen several cars (BMWs and not) that have refused to bleed. Problem is not that they don't bleed the air out, it's because certain leaks will be from the coolant system getting air pushed into it, such as a mildly blown head gasket. Other times the system loses coolant because it's getting sucked into a cylinder or two.

hopfully its just a blown head gasket i mean its almost has to be cause i dont have any AF i nthe oil owell ill check it out
thanks

:buttrock rock on

535power:

To add to what James said, the symptom you find "weird" is the one I find fatal: the engine will idle OK (not overheat) but the temp climbs when you drive it, i.e. the revs are up. This suggests to me that exhaust gases (hot, hot, hot) are coming into contact with your coolant.

Should the leakdown test point you towards the head (or gasket) you will want to have the head pressure tested and checked for flatness. Even if it is not cracked, it is likely to be warped.

Good luck! Larry F.

well sorry to say but happy to say.. you guys are wrong
yep i did the tests and no bubbles and 150psi on all 6 cyl,
i also took a spark plug knocked the center out and welded a air chuck male to it pluged the air in and with both valves shut no bubbles in the AF. so where does that leave me
have i stumped you yet?!? lol im still tryin to think what it may be i have the thing bled all the way, i dont konw im running out of ideas think i might just take it back to BMW and let them charge me out the a$$ for it
anythoughts?
thanks

Stumped, but Thinking . . .

James, any ideas?

i think i have brought this up before but i dont know thought it was worth sayin again.
ok i had a buddy of mine look at it and asked he me if there was a plate between the two big hoses(the elbow that goes from the water pump to the other side of the thermo and the other one next to it that goes to the top of the radiator) . he brought up a good point ...what is keep the AF from coming out of the block and getting sucked right pass the top radiator tube and goin back through the pump.. nothing its possible unless the flow is differnet than what we think... thus never goin through the radiator to get cooled... so is there suspose to be a plate there that seperates these to tubes and lines everything up in the correct direction? also where is the outlet for the AF that runs throught the block is it up front by the elbow and top raidator hose?
thanks again

Hi, 535power.

I do not know of a plate, as you hypothesize - and it is nearly impossible to assemble the hoses in the wrong order. When my E32 arrives home, I will hop out and take a couple pics of the hose arrangements, just in case (same M30 motor in both cars).

Still thinking . . . . :dunno

I had an experience with an E36 that would only overheat when driven hard. It would drive just fine for an hour or so, but when driven hard (raced) it would overheat in a matter of a couple of laps--coolant temps suddenly soared to 240F. It was a cracked head. Coolant pressure tests, compression tests, and other diagnostic tools showed nothing until the engine was torn down and inspected thoroughly. Another E36 had the same issue and would be fine for a day or so but suddenly overheat. After changing everything including the head gasket (not blown), we finally replaced the head. Problem solved.

Sometimes the car won't have any problems until the cylinder pressures and temps go up. The cracks can be very small but will allow cylinder pressures to pump air into the coolant system once you drive it.

I still think the head is cracked. M30 heads will crack fairly easily when overheated.

One quick question? When driving down the road about 50 - 60 MPH does engine temp drop? If not replace radiator. The object of the radiator is to exchange the heat from the coolant to air pasing through the core. Thus dropping the temperature of the coolant before re-entering the engine. Your core if partially clogged can not transfer heat. The vehicle is old enough so go ahead and replace it with a new one. Do NOT repair old radiator.

I had similar problem years ago, did similar checks. Eventually I replace the radiator with oversized unit (bought from ultimate garage I think)
The problem went away ever since...