BimmerFest BMW Forum banner

1995 525i Overheating

5K views 43 replies 9 participants last post by  SIRvive 
#1 ·
Had this car for a few years now, been reading posts and DIY's on this forum for a long time but never signed up until now...

I've gone through just about every post I could find about anything relating to the coolant system on my 95 525i.

So far i have replaced the radiator, water pump, thermo, and hoses. I do know the headers are NOT cracked, and the Aux fan does work.

Any other ideas of what could be wrong with it? Right now i am flushing the coolant from the engine using [http://www.bimmerfest.com/forums/showthread.php?t=523954] as a guideline. This is probably the 3rd or 4th time doing this. Yea i know crazy doing it over and over hoping for a different response.

The only thing i can think is maybe some air is trapped in the block. Any help is appreciated.

Thank you,
Bryan
 
#3 ·
Welcome to the Fest Bryan. A couple of quick things.

- Did you replace the fan clutch?
- Do you get heat out of the vents when the engine is warm (prior to it hitting the red area on the temp gauge)?
- Probably more importantly, did you make sure that your heater was on full heat with the fan on full blast when you bled the system of air? If not, re-bleed with the heater on full. It DOES make a difference.

These things can be finicky. Bleeding the cooling system can be a pain. Hang in there and for Pete's sake, don't let the engine temp get anywhere near the red mark. And, I hope you meant that you know that the "head" is not cracked rather than the "headers". A blown head gasket is always a possibility, but usually doesn't happen unless the car is allowed to overheat. I assume that didn't happen previously, right?

I used a trick when I overhauled my coolant system. While I had the t-stat out and the housing off (water pump in place of course), I ran a funnel into the opening and filled the block with coolant. Once it starter spilling out, I then put the T-stat and housing in place. It made bleeding the system much easier.

Anyway, welcome to the Fest.

Steve
 
#4 ·
Thanks for the fast reply's.

LVr: you are right. I meant the head gasket :p I had the heater on full blast and i was getting heat the entire time the car was on (from cold to 3/4 mark on temp), waiting for the engine to cool off now. If this doesn't work I will check the fan clutch. Thank you for the help. Bleeding this beast does seem very finicky. Never had a problem with any other vehicle I've bled before.
 
#5 ·
SIRvive said:
If this doesn't work I will check the fan clutch
:tsk:

Fully read the thread I linked to above. I'm trying to save you a lot of work.

Drilling a small hole in your thermostat is the secret. The reason the other cars were easier to bleed was because they use a poppet style thermostat (ie. they have a small hole in the thermostat that the BMW thermostat lacks)
 
#6 ·
Let me ask this. What prompted the coolant system overhaul? Did you do it as a preventative measure or was it the result of an overheat situation? Were you losing coolant with no aparent source of a leak?

If you were having no problems prior to the overhaul (meaning the car was running at normal operatiing temp) and you did it as a preventative measure, then your current overheating problem is likely coming from air trapped in the system. Although, it does sound like you were bleeding it properly.

If however, the overhaul was due to an overheat situation, then it is indeed possible that your head gasket may have failed. You probalbly already know, but look for white steam out of the exhaust, milky residue on the oil fill cap or milky looking oil on the dipstick. Any of these could signal a HG failure.

If you suspect a HG failure, then a compression check would be a good first diagnostic test.

Keeping my fingers crossed for you,
Steve
 
#8 · (Edited)
I have had great success with this procedure. Park on a incline, 50/50 coolant, fill the lower hose as full as possible to fill the radiator,connect it to the thermostat. Disconnect the upper hose at the radiator hold it up, pour in as much as possible to fill the block. Fill the over flow tank 3/4 full ,run the heater on high. tighten all hoses put the cap on the radiator. let her warm up releasing air every Minute from the bleed screw .As the normal operation temp approaches. if your not seeing a lot of air bleeding out along with coolant being pushed out. The pump has not caught prime and no circulation of coolant,It will quickly boil to over heat. There are many theory's as to cause and remedy of this condition. We can talk about all the ways folks do it and alternative fixes if needed.
 

Attachments

#9 ·
Good morning LD. I like the trick about filling the radiator with the lower hose and then connecting to the t-stat housing :thumbup: I will plan to give that a try next time.

... Disconnect the upper hose at the radiator fill as much as possible to fill the block ...
I'm a little confused by the statement above. I would think that the thermostat would be closed and that you would essentially be filling the top hose and that is all unless the t-stat is somehow open.

Are you using coolant that has been pre-heated or something like that?

Steve
 
#10 · (Edited)
I did something similar except I let the engine get warm while I boiled some coolant on the stove and them filled the upper radiator hose until coolant came out of the radiator. That was the only way I was able to get all the air out of my system. I had followed the bentley manual to a t and could not get all the air out my system the way it said to do it and that was the only idea I had left to try and get the job done.
 
#14 ·
Yknow, I've been on these forums for 2 years now and I've never had any problems bleeding my m50 engine without going through hoops. I really think we are overcomplicating a very simple issue.

1. Fill radiator up to the brim with coolant, with the bleed screw and rad cap off.
2. Start the engine and let it reach operating temperature.
3. Activate the cabin heater fully.
4. Pour coolant into the radiator until bubbles stop coming out of the bleed screw.
5. Screw the bleed screw in while coolant is spilling out of it.
6. Fill the radiator right to the brim, then screw in the rad cap tightly.
7. Drive the car for a day or two, then follow the exact same procedure that's listed above in the morning, when the engine is cold. This is not strictly necessary, but after getting spooked by bimmerfest, I just do it anyway.

That's it !! I've never had any problems !! I've done the exact set of things even after completely draining the radiator. Boiling coolant and filling this hose and that hose....c'mon, think about it, would they have designed the car's cooling system to be that complicated?

If you need to go through hoops to bleed the radiator, you're either overkilling the issue for the sake of peace of mind (which is fine), or you have other problems in the cooling system/engine matrix (which is not fine and needs to be traced).

rgds,
Roberto
 
#15 · (Edited)
I too have not had difficulty bleeding the system on my M50. However, the trick that I suggested (using a funnel to put coolant in the block) was due to my lack of knowledge that LD mentioned above. I was under the impression that NO fluid would circulate to the block until the t-stat opened and did not understand how the t-stat could open if there was no fluid in the block. I was incorrect in that assumption. I now understand that coolant can be circulated to the block via the opening in the head where the upper hose connects to the t-stat housing.

I continue to seek to learn more about our beloved E34's. Also, at one point, we were all new to the BMW and there is a steep learning curve. I am still on the upward side of that curve, continuing to climb, and will likely never get to the downward side. I don't forget from where I came and gladly share any tips that I can.

Hopefully all will eventually get the Bentley manual and learn to follow it to the letter, but not all have it yet.

Let***8217;s stay positive please.

Steve
 
#16 · (Edited)
Many are fortunate for not experiencing over heating after a repair or overhaul. The closed cooling system usually is quite reliable. But when parts start failing . recently this car was leaking coolant . the air was entering the block on cool down and causing problems . The cooling channels are very narrow about the size of a pencil. Now Add 20 years of use and abuse. The effects of hard water and a 12v iron block grounded elect system . Now cooling channels and Rads can clog from electrolysis if not flushed at least evey 5 years. Trapped air behind the thermostat and in the head prevents the hot coolant from circulating at full prime. Its no fun over heating so many cases of over heat in the closed system cars from fatigued parts . A friend saved his m50 by not driving on a over heat from a old plastic w/p the the shaft bearings seized and the shaft was leaking water and taking in Air. Sweet car too 325 with a m50. we saved it by replacing the bad pump with a brass pump i had filled and bled it using the process described earlier :)
 
#17 ·
Update on the Bimmer :D

Well, I did what Radian posted. Drilled the little hole in my thermostat. I rechecked my oil to make sure it wasn't turning creamy. Check the fan clutch with the old cardboard in the fan. The fan clutch is shot, ordered a new one so should have it in the mail by the middle of next week. Thank you all for the help. I'm just glad I this big blue girl could be saved.
 
#20 ·
Only someone who has experianced the loss of prime due to air,can understand how difficult and frustratin it can be. The important thing is we both found a way to make it work. your s a warm engine mine a cold engine. I watched a expert bmw mechanic fill and bleed the radiator in intervels through the bleed screw took about 15 mins, but he was sucessfull on a cold motor to regular opp temp. The point is do what works ,even when the regular ways dont work.:)
 
#24 ·
Just curious. Can we run the car momentarily for a week or so without coolant to check for leaks etc after a radiator flush. This could save coolant wastage due to a probable leak. Will it harm the engine in any way? I mean no more than 50 to 100 miles without coolant.
 
#25 ·
Absolutely not. Never drive a car without coolant, or at least water. If you want to save money, use water without coolant (i've done this with no problems for weeks), and add coolant later.

However, you want to use coolant, especially if you want to check for leaks. I mean, sweet smelling, cheap, luminous green, non-bmw coolant. If there are leaks, the bright green droplets will make it more obvious....you might miss it otherwise. And its so cheap....just get the stuff off the shelf. Its cost like US$5 or less, compared to nearly $20 for oem coolant. So there is no need to save money either when its so cheap.

Flushing a radiator should not lead to leaks. However, I like the way you're being anal about your time machine mr president. :) That will keep it that way much much longer.
 
#32 ·
if you are having that much trouble bleeding the system, may i suggest a compression check. if the head gasket has failed, you will get combustion gasses pushed into the coolant making bleeding impossible. i have a 325 m50 with this condition right now and i know the car was run hot.
 
#33 ·
Part is suppose to be at my house today. So hopefully i get my baby fixed, inspected, and possibly up for sale :( Need a bigger car now that we have another baby on the way. No way to fit two adults, two children, and two dogs in my bimmer comfortably. Happy about the baby, but sad about my wife saying i have to sell my bimmer.
 
#36 ·
Got the overheating problem fixed. :D

Took it to be inspected this morning... and of course it failed the smog test..

HC(PPM) high speed Standard 220, i had 227... low speed standard 220.. with 644...
CO standard was 1.2 and i had 2.16 at high.. and for low 1.2 i had 3. Guess thats what i get for letting my car sit for a year in my garage. Im going to head to autozone or some autoparts store to try and pick up some seafoam.
 
#39 ·
Yep. Replaced the fan clutch for the fix.

Now I'm just getting white smoke out of the exhaust but I'm about 99% sure that it is from the carbon buildup from sitting. I know its not a cracked head gasket.

Just need to add brake fluid (DOT 4), seafoam the crap outta the spark plug area, and put some new sparkplugs in.
 
#40 ·
White smoke does not equal carbon. White smoke is engine oil burning in the combustion chamber due to worn piston rings, or steam due to coolant seepage into the combustion chamber or excess water in the exhaust pipes that got there somehow.

Carbon translates into black smoke.
 
#41 ·
I'm thinking its from the gas sitting in the tank for a year and a half. water and gas separate.. causing steam and an excess amount of carbon. :/ The emission tests show this and the mechanics at the inspection location figured the same since we know the head gasket isn't blown.

If I'm incorrect please advise. Going to run the seafoam through the spark plug inserts, let it clean overnight.. do it again the next day, then add some cleaner to the fuel. take it out on some old country roads and put the pedal to the metal, hopefully cleaning the system out enough to pass inspection. :D
 
#42 ·
if you are getting white smoke and still overheating after putting fresh gas in and running the car for a while to warm it up and burn up water from sitting, why are you convinced the head gasket is ok? believe it or not it is a common problem on these and yours sure sounds like it. fwiw.
 
#43 ·
What you could do is to fill up the tank to the brim with regular gasoline. It will mix with the separated fractions, especially as it rushes in at high pressure, and this would mitigate the problem. Seafoam will do nothing for this situation, and pretty much does nothing for the spark plug wells either.

You don't need to goto country roads if you don't have the time. Just gun the engine at idle to 5k rpm and hold it for 5 minutes. The engine will not overheat. This, of course, if no one else lives near you.

Why did you take the car for an inspection if there was white smoke coming out of your tailpipe?
 
#44 ·
Cars not overheating anymore :D to the op.

I do live by other people, but it should be fine. They are used to me working on vehicles.
Took it in just hoping it would pass. Last night it when the smoke started coming out, checked it again this morning but nothing happened so i took it in. It rode pretty decent on the way there. I filled it up to the brim with 93 since 91 wasn't available :/ they only had 85, 89 and 93.

Thanks for all the help.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top