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E34 (1989 - 1995)

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  #1  
Old 01-19-2014, 10:50 AM
dpglenn3 dpglenn3 is offline
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Mein Auto: 1992 525i
Overheating

New to the forum, have studied several threads on overheating and referred to the Bentley manual.

We own a 1992, 525i, 175K miles, automatic. The car ran low on oil a few years ago and overheated. We have kept it running ok since that incident and it is shared by a couple of our teenage sons. A little more than a year ago, we had a local indy mechanic install a new water pump, high temp thermostat and fresh belts and hoses along with a new ac compressor. The coolant system parts came from BAVAuto, the water pump with the metal impeller.

Appeared to work ok except the normal operating temperature on the gauge was a little past the midway point and we started having overheat issues at idle, while underway the temperature would settle back down to normal zone though always a little over midway on the gauge.

The car was driven several thousand miles with this intermittent problem always keeping a close eye on coolant and oil levels. One of our sons came home in the car the other day and said the temperature gauge was pegged on full overheat. He did not drive it far on the overheat, actually pulled over at first sign, looked over fluids and waited to bring car back home, a couple of miles. We let the car cool, we checked levels and things appeared ok, went for a quick road test but the gauge jumped to the danger zone within a short trip and we brought back to the barn.

Assumed that we had a radiator failure, thermostat failure or water pump failure. Replaced all three items paying close attention to reinstalling the thermostat in the correct orientation. topped off the system, went through bleed procedure though could not get it to bleed through bleed screw, ran the car about the same distance, having the same problem, full overheat. Let sit overnight, expansion tank in morning was empty, topped off to cold mark and cranked up.

We put a heat gun on the system and shot numbers on the head, radiator and thermostat housing to try and verify when the thermostat should open, approximately 180 degrees and we should start getting coolant flow through the system, we cannot verify if the coolant is flowing, in fact it seems like it is obstructed somewhere the upper hose was hot and but the lower hose never felt like it was getting any coolant flowing through it???

1. does the system flow from the engine into the upper hose through radiator and return to the engine through the lower hose?
2. has anyone heard of an obstruction in the head or block that would shut this flow down?
3. does it sound like a bleed issue?
4. can a bad heater valve create an overheating issue of this magnitude? I am not able to get any heat in the car at and above normal operating temperature with all the vents open???

Thanks for any guidance.

Last edited by dpglenn3; 01-19-2014 at 11:39 AM.
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  #2  
Old 01-19-2014, 10:26 PM
Mamij Mamij is online now
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Mein Auto: BMW 320i M52 1996
My compliments on an outstanding first post. It has more sequential details that most and is correctly expressed in flawless English with rules about paragraphing and grammar honoured as they should be.

To answer your questions first :

1. does the system flow from the engine into the upper hose through radiator and return to the engine through the lower hose?

Yes.

2. has anyone heard of an obstruction in the head or block that would shut this flow down?

No.

There is such a thing as super rust or super crap in the system but it would have to be a lightning strike probability issue for it to result in actual blockage of this degree. Regardless, when you changed your radiator, you should have flushed out your entire cooling system and this should have taken care of any such risks.

3. does it sound like a bleed issue?

No.

The M50 and subsequent BMW engines cannot be screwed by air pockets left by bad bleeding. The cylinder head is designed to evacuate bubbles to the radiator without passing through the thermostat orifice first. There are two openings in the head created to facilitate this. Please see :

http://www.bimmerfest.com/forums/sho...d.php?t=731991

Only insufficient coolant added to replenish water levels which adjust to compensate for air pockets introduced during a system flush (such as would occur when you change the radiator) would cause overheating (due to insufficient coolant) , but you seem to be on top of that.

4. can a bad heater valve create an overheating issue of this magnitude? I am not able to get any heat in the car at and above normal operating temperature with all the vents open???

No.

The unpowered position of the 2 valves in the heater valve unit is closed. Coolant will bypass the heater and return to the engine. Even if they were somehow stuck open, as long as your coolant levels in the expansion tank are ok, you wouldn't have a lack of coolant. Btw, you are supposed to have set your cabin heat to hot when you bleed the system. And btw there may be a way to rescue your heater valves - chance of success would be 20%. Please see :

http://www.bmwe34.net/E34main/Mainte...eaterValve.htm

============================

You need to check your fan clutch and your auxiliary fan.

Please search these forums for the methods to check on your fan clutch. Basically, if it is difficult to turn while cold (with the engine off) and, when the engine is heated up and running, the fan clutch does not immediately stop once you shut the engine down, but keeps spinning fast for anything from 5-10 seconds before stopping, then your fan clutch is busted. A failure in either test justifies close inspection and most likely a change in short order.

Please study and check this link to check if your aux fan works, and works at both low and high speeds :

http://www.nmia.com/~dgnrg/page_20.htm

That your car used to run hot while at idle (but normal temp while underway) indicates very strongly that both your fan clutch and your aux fan are not working problem. If the clutch fan fails, the aux fan will run at low and then high speeds and maintain engine temps at not more than 1 needle's width above 12 oclock.

====================================

This is not a difficult problem to trace and fix if you are methodical about it.

You should also do the stomp test for good measure and download and familiarise yourself with the bentley manual (both of which can be found at the stickies at the top of the forums).


====================================


A word of advice. If you ultimately trace and *verify* that the issue is a headgasket or cracked head situation, use a block sealer first before going for a full rebuild. I personally dump in a block sealer with every coolant change every 2 years, as a form of insurance. Instead of a block sealer sold on the market, you can just purchase 40% sodium silicate solution (32 oz) and add that to your expansion tank when you are refreshing your coolant. Sodium silicate is the active compound in block sealers, and its cheaper to buy this directly from a hardware store or pharmacy.

However, don't worry about this scenario. The M50 engine is able to take many many overheats without any HG or cracked head issues. Strong bugger indeed. That said, adding the block sealer is highly recommended.

Good Luck.


p.s. It might be a good idea for you to use a new radiator cap. It only costs $8 oem. You already have a new bleed screw, would have come with your new radiator. Sell off your old radiator on ebay for $50. Its good. Short of physical damage, radiators almost never need changing.

p.s. Check your various radiator hoses for leaks and loose clips/clamps. Apart from the two big ones, there's a long octopussian one under the intake manifold, and there are hoses leading to and going away from the heater valve unit. Its a good idea to use strong smelling and brightly coloured coolant to more easily detect leaks.

p.p.s. If you truly suspect blockage due to rust (if you saw alot of it while changing your old radiator out, and you still see it in your current expansion tank), then use a radiator flush with chelating agents (i.e. chemicals that can actually remove rust) such as Prestone's Super Flush. Read the label to make sure that chelating agents are there. To my knowledge, all the flushes on the market are rubbish, except for Prestone and Cummin's Restore plus (but this is very expensive).

Last edited by Mamij; 01-20-2014 at 02:42 AM.
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  #3  
Old 01-20-2014, 04:25 AM
dpglenn3 dpglenn3 is offline
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Mein Auto: 1992 525i
Thanks for the detailed feedback @Mamij. I'll study the links you suggest and get into the fan clutch and aux fan troubleshooting. I'll post results. I like the idea of the block sealer insurance as well. Kind Regards.
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  #4  
Old 01-20-2014, 07:07 AM
E34ZombieHunter's Avatar
E34ZombieHunter E34ZombieHunter is offline
Nothin like an E34
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Mein Auto: 95 540i B/B
Try to clean the heater valve, i bet if more people tried this you would not spend 100$+ on a new one. I have had great success, they get clogged, it happens.

This also could be contributing to the overheating; if the heat was not set to full blast, or in your case, not working, the system was not able to be bled properly.

Also see my signature for the proper fan clutch action.
Do the newspaper test, you should not be able to stop the fan when it is engaged.
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Gotta love an E34!!
If you want to get junkyard parts remember one thing, if it was wrecked you know it was running/driving. You may not know how well, but it was.

READ THE STICKIES AT THE TOP OF THE PAGE!!

STOMP TEST

READ ME IM THE BIBLE

FAN CLUTCH

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  #5  
Old 01-20-2014, 11:16 AM
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Doktor Bert Doktor Bert is offline
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Location: Palm Springs
 
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Mein Auto: BMW 525i
Have seen many of the plastic water pump impellers fail and kill these engines....FWIW
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  #6  
Old 01-20-2014, 12:37 PM
Mamij Mamij is online now
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Mein Auto: BMW 320i M52 1996
Quote:
Originally Posted by E34ZombieHunter View Post
Try to clean the heater valve, i bet if more people tried this you would not spend 100$+ on a new one. I have had great success, they get clogged, it happens.

This also could be contributing to the overheating; if the heat was not set to full blast, or in your case, not working, the system was not able to be bled properly.

Also see my signature for the proper fan clutch action.
Do the newspaper test, you should not be able to stop the fan when it is engaged.
Hi Dionte @ whatever it is now and thanks for that great video. I might need it someday but thankfully today is not that day.

However, I don't agree with your reasoning here and I feel you are perpetuating a false forum myth.

If bubbles or stuck heater valves/cores would be a problem, then simply shutting off the cabin heat would cause the engine to overheat instantly.

The engine cooling system is connected to, but not dependant on, coolant circulation through the cabin heating circuit. Blockages there do not create overheating. There must be bypass hoses or whatever. This is by design, obviously...why build in a weakness when you can avoid it easily?

The M50 and later engines do not suffer from trapped bubble induced overheating problems like earlier engines. Read and think through the link I posted above and you'll understand why.

The M50 engine is inclined at a slight angle. Air bubbles from the back of the engine naturally move to the front without power, and coolant moves back to replace the air bubbles due to gravity. This process is only accelerated not retarded, when the engine is running.

Please do not perpetuate this myth i.e. bad bleeding causing overheating - any further. That unfortunate fate only applies to the M20 and M30 engines.

Bentley asks you to activate cabin heat when bleeding in order to be more efficient, so that one bleed and one topup is all you require to finish the job.

The OP has stated that she topped up her expansion tank shortly after the rad change, which means she has compensated for the replacement of coolant that has moved out of the expansion tank into wherever air previously existed. This means she should have sufficient coolant in her engine.


========================


OP lets take shortage of coolant out of the equation. After all, you could have screwed something simple up - everybody's been there. Please do the following for our benefit. It will only take you 15 minutes and cost you nothing. Ignore everything else you might have read elsewhere. Follow my instructions strictly.

Make sure your car is on generally level or inclined ground. Never do this on a decline with the nose pointing downwards.

1. Remove the rad cap and bleed screw.
2. Fill up coolant/water in the expansion tank until it runs out the bleed hole and all bubbles have stopped coming out.
3. Start the engine and leave it at idle for 8-10 minutes to reach normal operating temperature. Do not replace the rad cap and bleed screw and do not rev the engine. [ If your cabin heat is working activate cabin heat if not you can leave it alone. ]
4. Once you've reached optemp, add more coolant to the expansion tank until no more bubbles run out of of the bleed hole.
5. Replace the bleed screw. Do not overtighten - snug will do. Threads get stripped easily.
6. Top up water/coolant to the brim in the expansion tank.
7. Replace radiator cap. A tad bit of coolant will spill and this is fine. Your expansion tank will be full of coolant right to the cap and this is fine. It will slowly fall to and stabilise at the halfway mark over 6-8 weeks of continuous driving.

All of this should take you around 15 minutes at most. If it takes longer, you're doing something wrong.

Leave the car at idle for a further 15 minutes while watching the temp needle. If it remains normal, then go for a short drive. If it remains normal, then go for a short but a high rpm drive in second or 3rd gear. If that remains normal, then go for a longer drive on the highway. If that remains normal....well then you're done. Keep monitoring over the weeks.

Whistle while you work.

Report your observations swiftly.

========================

Even with a busted clutch fan and aux fan, you should be running at normal temperature while on the highway, even with the a/c switched on. You'll only run into trouble when you're stopped or at slow city speeds.

If you're overheating on the highway, prime suspects would be coolant loss through a leak, or water pump failure and to a lesser extent thermostat failure.

P.S. Once again, please check all your radiator hose fittings, clamps, clips etc to confirm that they are good and tight.
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  #7  
Old 01-20-2014, 04:22 PM
dpglenn3 dpglenn3 is offline
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Mein Auto: 1992 525i
Ok Mamij and ZombieHunter, thanks for the effort and feedback regarding my overheating issue. I have gone through the last excercise, 1-7, and she has stabilized at normal operating temp at least through a short drive, I have to travel rest of week and will be back to chase the heater valve issue on Friday. I feel like the overheat following the installation of the new radiator, water pump and thermostat has been a result of a poor flush/bleed on my part. I am not yet confident that I have successfully bled properly and will monitor over this coming weekend and get the car out on the highway. Also plan to test the aux fan and clutch fan. Again, many thanks for the feedback.
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  #8  
Old 01-21-2014, 09:17 AM
Mamij Mamij is online now
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Mein Auto: BMW 320i M52 1996
Hi OP,

Firstly, this is not a bleeding or air pocket issue. This is an issue with a lack of sufficient coolant (as it appears now).

Secondly, you need to investigate why your car overheated recently, to confirm that you've killed the problem. Put your old thermostat into a pot of boiling water. Does it open up easily ? Remove it with tongs and set it on the table. Does it close up easily? Then that's not the problem. (see youtube for vids on this).

Hold the old wp and turn it. Does it turn with difficulty ? Do you hear or feel any grinding sounds ? Is the wheel caked with rust (some rust is ok) ? If not, then its not the wp.

I seriously doubt it was your radiator but just take a look at it anyway and see if anything appears to be off. Actually, you can immerse it in your bathtub after closing off the in and out ports, bleed hole and expansion tank, and see if bubbles come out from anywhere, indicating ruptures.

An overheat will cause you to lose coolant simply by venting so it may be hard to tell if you had too little coolant before.

Then check your fan clutch and aux fan (at both speeds).

Get a new rad cap. Get a spare new bleed screw and keep it in the coin compartment for emergencies. It happens. They are both really cheap. Only OEM for the rad cap and any decent brand for the bleed screw.

===========================



After all that is done and any problems found are corrected, then come to your heater valve assembly.

Follow zombie's video and fix your heater valve assembly. Before dismantling it though, try the procedure on e34.net that I linked much earlier - if it works its much much easier. Remember to properly tighten down the screws properly after that !

Once your heater valve is working again, it is time to flush the cooling system.

===========================


Recover your old coolant as best as you can (the radiator has a drain plug you'll get 50% that way, so that's about 5.5 litres of mix) and flush your radiator with running water. Go for a short drive with water alone for at least 15 minutes following bleeding, come back, shut down the engine and an hour later flush once again with running water. Then drain. If the water coming out still looks rusty, repeat if not stop here.

===========================


Now apply the block sealer. Don't spend more than $25 on this.

Add 1 litre of sodium silicate or a market block sealer (forummers have used Moroso's ceramic sealer, Bar's leak, and Blue Devil, with success, and all of this is compatible with coolant) to your radiator, and top up with coolant and water till you've got the correct concentration (consider the block sealer to be water).

Go through the 7 step bleed process listed earlier (activate cabin heat), but this time after closing the rad cap, let the car idle for a further 35 minutes for a total idle time of 45 minutes. The block sealer would have finished the job. Drive. Monitor coolant levels daily when cold, and top up once it falls below the halfway mark.

Sharp falls in coolant levels, if any, will disappear within 7 days of regular driving. After that you can check once a week until it stabilises at roughly the halfway mark.

It is not necessary to flush the cooling system before applying a block sealer, but all the block sealer companies recommend it because so few people flush their systems over the years. Most older cars are poorly maintained. However, if your heater core/heater valve etc has become blocked, please fix that and then flush the system to eliminate debris from the cooling passages, and then apply the block sealer.

Please update your thread with your results and observations once you've done all of the above. Good luck.
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