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535i coolant system problems.

18K views 56 replies 12 participants last post by  snowsled7 
#1 ·
I have recently bought a 89 535 and i had done a few work to it because the previous owner had absolutely no idea what they were doing. i had to had the starter rebuild, they replaced the fan and clutch with an electronic fan. i had to install a thermostat since there was no thermostat to begin with. now when i run it and get it to operating temp., the hoses going to the radiator becomes stiff like theres a lot of pressure in the hose. and every time i bleed the coolant, only coolant comes out and no air. so as of right now im stumped. should i be looking for a clogged hose, or should i replace the radiator. also will this cause the engine to run rough after warm up when pressure is build in the hoses?
 
#2 ·
It is normal for the radiator hoses to be under pressure when the engine is at operating temperature. I prefer the engine driven clutch fan to an additional electric. With the proper thermostatic swtich the electric should work fine.

Is the car overheating? Is the car losing coolant?

Is the car running rough as well?
 
#3 ·
its not losing coolant and the temp gauge stays at the middle line. the hoses seems to have a lot of pressure though. sometimes it feels hard like a rock and i know that isnt normal to any car.
once i start it up the engine will run fine idle like it should, then once i drive it for a little bit and when the temp gets to the middle line on the gauge, it starts to idle rough. but when i give it gas sometimes it smooths it right out and sometimes it seems like it dropped a cylinder or two.
 
#5 ·
its not losing coolant and the temp gauge stays at the middle line. the hoses seems to have a lot of pressure though. sometimes it feels hard like a rock and i know that isnt normal to any car.
The cooling system can presurize to 15 psi and still operate normally. Beyond that you will get pressure release from the cap at the resevoir at the base of the windshield.

If the car is not overheating, and not losing coolant, there isn't likely a problem.

The one thing that can overpressurize the system is a blown headgasket but it would also cause overheating and coolant loss.

once i start it up the engine will run fine idle like it should, then once i drive it for a little bit and when the temp gets to the middle line on the gauge, it starts to idle rough. but when i give it gas sometimes it smooths it right out and sometimes it seems like it dropped a cylinder or two.
This could be any number of tune-up items, plugs, wires, cap, rotor, fuel filter, injectors, vacuum leaks, idle control valve clogged or bad, throttle position sensor, O2 sensor, valve adjustment. Download the Bentley manual for the car and start diagnosing and replacing worn tune up items as needed.

Whatever you do, I wouldn't put diesel fuel where it wasn't intended to go, in hope of finding some miracle liquid cure for your car.;)
 
#6 ·
well i decided to leave the cooling system alone and drove it for a while. and just until a few hours ago it started to over heat on me. as in the temp kept going higher, so i pulled off and open the hood and saw steam and dripping coolant from the coolant expansion tank. i let it cooled for a little bit and started it up and right away the gauge went right down to operating temp and was fine... so my question is what the F@#* did i get myself into buying this car?!?!
 
#12 ·
Was there a reason why the previous owner removed the thermostat ?

You need to do alot of troubleshooting before you jump to conclusions, and it is likely that you'll need to do stuff anyway just to be safe. Since the overheat ocurred after your repair, there's a good chance that you either did not do it right, or the thermostat was busted though new (it happens).

Try removing the thermostat and driving that way. There's no harm to the car with the themostat removed.....the engine will just take longer to heat up to operating temperature.

You should check to see if your WP (water pump) is working. Pull out the top radiator hose off the radiator, start the car, and see if water spurts out. If it doesn't, then your wp is busted.
 
#7 ·
Relax man, its just a car, they all have issues at one point or another. At least you saw this coming and got feelers in there.

I start with a coolant flush, fill and bleed and take it from there.
 
#9 ·
Just curious...

Did you rule out a head gasket problem?

Is your heater control valves working properly?
Does it make a difference when you turn on the heater?

My car has been going about a needles width over TDC on the guage, and causing me some concern, so I'm paying attention to the advice of posters.

Supertech777, I had to go to RealOEM, just to assure myself that I had installed the thermostat correctly, even though I was quite certain I did.
New water pump, and new rad, but still the same on the guage.
What, in your opinion, is the proper temp degree for the therm?

I am having another interesting thing happen concerning the cooling and A/C, but I will start a new thread.

Thanks for the continuing education.
Hb
 
#11 · (Edited)
the cooling channels in the block are so thin and small, given the amount of coolant passing through the block (not sure if youve ever drained the block but its alot) would cause a pretty good deal of pressure which would make the chances of something small enough to fit in there get stuck slim to none. a radiator block or clog is much more probable.

I agree with the system overhaul. New sensors and hoses and clamps and housings and gaskets and all of that with a true flush (block included) and proper bleed.

Did you bleed the car right? the heated air left in the system could expand causing all of that pressure you feel in the hoses, and ultimately an overly hot engine...

I'm not sure of the exact way to bleed the air out of an M30, or if its similar to an M50. I know the M60 is a self-bleeding system...
 
#13 ·
On lunch break so I'll be quick.
I will go into detail if not understood later.

For there not to be a thermostat already in the car is a tell.
Usually done to cover up a bad WP, clogged radiator or worse.... BHG (blown head gasket)

However let's not get ahead of ourselves.
Test your current thermostat in a pot of hot water.
If it opens your good.
Let it cool (this is where people don't pay attention) If it doesn't close the thermostat is bad.
Make sure you have a high temp thermostat.
If you don't have one get one.

Drain the system and remove the radiator. Then flush it.
Flushing the entire cooling system at once is good. But I've been down that route your on.
So to be safe I remove the radiator and flush it separately first.
Reinstall radiator.
Flush the entire system
refill and bleed, bleed, bleed.

If that doesn't do the trick then check you wp.
Next would be to inspect your sensors (one on the radiator, one on the thermostat housing)
If none of these solutions work... BHG.

The Idle issue can be from various things. Without much detail on what's been done to the car and when does it occur... it can be anything.
As well most m30 cars have a bit of a lumpy idle.
 
#17 ·
Most points covered here. If the water pump is suspect ditch it rather than 'test' it. Cheap insurance.
 
#18 ·
You need to find out why it is overheating. Doing another flush, or a flush at all is unlikely to cure the problem, and when you go to fix the problem you will be wasting expensive new coolant. If the radiator, fans, water pump and head gasket are working, it will run on garbage coolant. Just save it for last, save yourself time and money.

I would also FIRST verify the condition of the headgasket. There are chemical tests that detect combustion gasses in the coolant. Check the oil for milky color. Stop driving if you see oil in the coolant or vice versa.

If the headgasket checks out, go for the cooling system overhaul and thorough system flush. It is impossible for us to know from here what the condition of the radiator is, or the water pump, or the H.G. There is more work to do.
 
#19 ·
I agree with just replacing the WP. If its suspect, replace it, as stated before, cheap insurance...

A poorly flushed non-bled system would cause over heating. Air becomes pressurized with heat (think hot air balloon if it helps; I know it's not a pressure thing, but temperature causes deferent properties for gases). A lot of air in the system could cause many cooling issues which is why there's such an emphasis on the bleed bleed bleeding.

I wish OP would check back, so we can get some closure or an update.

I think that this is the order of events that's needs to happen here OP:
 
#23 ·
A poorly flushed non-bled system would cause over heating. Air becomes pressurized with heat (think hot air balloon if it helps; I know it's not a pressure thing, but temperature causes deferent properties for gases). A lot of air in the system could cause many cooling issues which is why there's such an emphasis on the bleed bleed bleeding.
It would take a lot of air. No offense but changing coolant to fix an overheating problem is akin to changing trans fluid on an auto trans that wont go into reverse. It just isn't going to fix the problem. Find the probelm first, do fluid maint after the actual fix is made.
 
#20 ·
i checked the oil and there isnt a milky color, the exhaust doesnt smell or looks like its burning coolant so i think the head gasket is fine. is it possible that the hose from the rad to the expansion tank is clogged and/or the expansion tank has some issues.

also where on the block is the drain plug?

also i bled the system using the bleeding screw on top of the thermostat housing and after a while of bleeding it it stopped having air come out. it hasnt over heated again so far.

now my last question, if the rad has a little damage to one of the ports but isnt leaking, would that cause a problem too?
 
#24 · (Edited)
i checked the oil and there isnt a milky color, the exhaust doesnt smell or looks like its burning coolant so i think the head gasket is fine.
Unfortunately, that's not a very thorough inspection. Taking it to a shop and having a technician perform a leak-down check on each cylinder is the best way to go.

also where on the block is the drain plug?
On the passenger side of the block, towards the rear, underneath the 5&6 exhaust ports. Don't remove it until you have a new copper gasket to put in place of the old one...otherwise it'll leak.

also i bled the system using the bleeding screw on top of the thermostat housing and after a while of bleeding it it stopped having air come out. it hasnt over heated again so far.
That's good. Now would be the time to get it over to a shop for a better look. This isn't unique to BMW's, it's just something you have to do with any old car, for peace of mind. :dunno:

now my last question, if the rad has a little damage to one of the ports but isnt leaking, would that cause a problem too?
What do you mean by, "....a little damage"? :confused: Got a pic?
 
#21 ·
Your last question is "possibly". Any details about this "damage"?

The drain plug on the block of my M50 is under the exhaust in between the 5 and 6 cylinders...
 
#22 · (Edited)
We still have not determined the cause of the overheat. The system has reportedly been flushed and bled, not exactly a complex procedure. Vry doubtful that is the cause.

It is highly unlikely that there is a blockage in a hose.

As mentioned, more info on the damaged radiator.

Did it overheat on the highway at speed, or in traffic, stop and go?
 
#29 ·
Once many moons ago, I bled my radiator 7 days after I had flushed and bled it, and I found tons and tons of bubbles coming out. The engine had performed flawlessly through constant hard driving in the intervening period. Imo, it is very difficult for one to trap so much air in an engine, even by someone who does a bad job of bleeding it or does not bleed it at all....that it leads to overheating. The wp keeps things circulating and air pockets tend to naturally collect in the expansion tank and the channel where the bleed screw is located.
 
#30 · (Edited)
Something I said but not gone through in detail.
90% of the overheating problems I've noticed, heard and experienced is the circulation of coolant. So a rebleed isn't completely out of the question.

OP IMO make sure it was bled correctly:
reso cap off
car running
heat on full blast
fill reso till coolant starts to climb
immediately replace cap
shut car off
turn screw on thermostat housing to bleed out air bubbles,
Repeat till no air bubbles come out

I think you stated there's no oil /coolant mixing going on. That's a good thing.
If there's no coolant in the oil or vise versa usually that would rule out a BHG.
However that's not to say it's not possible.

Flushing the radiator separate will insure you get all that 20+ year old crap out of the radiator. For if it's the original one. I can almost guarantee it's got some crap in it.
Don't use a flush. Just water from a water hose. Hit all three holes... hehehe. But cover one so some type of pressure is there.
The flush solvents eat at the aluminum.
Doing this saves you from having to buy a new one. I did this twice on two different e34s. Both times there was all types of mess it there.

IIRC the WP would make some type of noise signalling it's about to fail. (at least mine did)

As well here's something else to consider. This is M30 specific.
Let's say the coolant has been bled correctly, wp is okay, no BHG, and the radiator has zero blockage.
(something you wouldn't know unless you removed and flushed the radiator through all 3 holes)

It may be your sensors. There are 3:
2 in the thermostat housing
one in the radiator.

The one in the radiator and iirc the blue sensor on the thermostat housing are the most common to go. These regulate the temp and would mimic a overheating issue.

Before I left atlanta. I replaced my radiator and thermostat for the ride north.
The car read death hot. Being I knew I had no issues with the WP, nor did I have a BHG.
I chaulked it up to the sensors for I nor the the PO changed them out.
Once I changed them out the car went back to normal.

just my .02. Back to work. Lunch is over :(
 
#32 ·
Something I said but not gone through in detail.
90% of the overheating problems I've noticed, heard and experienced is the circulation of coolant. So a rebleed isn't completely out of the question.

:(
In my observation, unless you're trying to get air into the engine, its almost unheard of to bleed it badly and yet have enough air in it to cause overheating issues.
 
#31 · (Edited)
Yes, some free play may indicate a bad wp but that's not decisive at all. 2 weeks ago, I changed out a 1 year old water pump that had some free play in it when i yanked the fan clutch attached to it. Coolant circulation was perfectly fine, and the pump turned fine when removed and inspected, and all of its fins were still on it. From other overheating threads that I have seen here, short of a wp leak, it is difficult to tell by on-engine inspection if your wp is alright or not, and failing wp may not make noise along the way. The only way to tell for sure is through coolant flow, which can only be observed by detaching the upper radiator hose at the radiator fitting, moving it a little to the side, starting the engine and then looking at how much water is driven out. Even then, its best to have an idea of how much coolant would flow if the water pump was working perfectly, to have a baseline....so until then, you'll have to use a guesstimate. Detailed instructions on how to do this have been listed in one of my earlier responses above.

That being said, if you can detect any free play (with the engine off) or noise or uneven movement in your wp (while running), you need to get that changed asap no matter what, and its best to carry 5 gallons of water in your trunk until you do.

Since the po took such wonderful care of your car, and since you've already flushed and bled your radiator and changed the thermostat, I'm willing to bet that your wp is defective.
 
#33 ·
You guys are all making recomendations without even knowing the symptoms...

He said it overheated. How/why did it overheat? This is very helpful information unless you plan to just throw money at it.

Overheated in traffic = lack of airflow, fans etc.

Overheated at speed = most likely water pump.

Headgasket failure will cause problem all the time and get increasingly worse with time/use.

So go ahead and suggest throwing parts at it but, you will be lucky if you fix it. You definately wont save any $$ using this method unless you guess right the first time.

As mentioned, eliminate the HG as a possibility first, using actual testing, not just your observations.
 
#34 ·
The entire cooling system generally needs to be overhauled for our car when it reaches this age, so throwing parts at it is not a waste of time, besides there are ways to test the existing parts before replacing them.
It is also possible that more than one cooling system problem is at play here. The wp and the HG could both be gone. Everything needs to be tested/flushed/bleed/checked in any case, and that includes the HG, since its just a cheap solution that you need to purchase to quickly test for it. Even if the test is negative, you'll feel the satisfaction of the assurance that the HG is in good shape. I'm guessing that the bottle probably has enough test solution for a total of 3-4 tests. If so, I would test the coolant solution for HG problems once every year.
 
#38 ·
The entire cooling system generally needs to be overhauled for our car when it reaches this age, so throwing parts at it is not a waste of time,
No, but if you are on a budget, fixing the immediate problem is the more cost effective way to go. I never assume folks with $1500-3000 cars can afford $1000 in parts for them tomorrow.

I thought you were a fan of saving money? The way to do that is to try and accurately diagnose BEFORE proceeding.
 
#41 · (Edited)
You deliberately draw internal comparisons that are not appropriate, and some of your replies where you stubbornly refuse to move beyond your comfort zone make me truly wonder if you have any real understanding and confidence with automotive systems. You remind me of a good friend of mine, which is why I'm not going to argue further here as I know its pointless. I will call him up and yell at him instead. :)

Doing anticipatory repairs, be they no start ones or commonly neglected cooling system components, especially when these are known quantities, saves time, money, and stress overall, and creates peace of mind. Most people mmay have some facility in working on their cars and enjoy it as a hobby in general. However most people are not mechanics, and would rather not be forced to become one due to their cars,

That being said, there is alot to be said about your general posture where you prefer to know the car and develop a personal skill well enough to efficiently diagnose and fix problems as they occur, which saves much more money over the long run if you are purely lucky and nothing much goes wrong with the car, even if there are very commonly known problems for our model. This may not be an obviously foolish way to proceed. In fact, it is debatable as to who is actually being more conservative.

It may boil down to how you look at things. Let us agree to disagree. People will make up their own minds when they read both of our writeups.



rgds,
Roberto
 
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