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E34 (1989 - 1995)

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  #1  
Old 05-25-2011, 09:37 AM
bladex10 bladex10 is offline
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Mein Auto: 525I
525i overheating problems

Let me start off by saying a couple days ago, this bmw started overheating and the gauge just flew to the red zone. I replaced the thermostat yesterday, bleed the system and it all seemed good. idled for 25 mins with no overheating at all, drove it 25 miles no problems. Parked car and came out to a puddle of coolant under car with no ideas on where it came from. Couldnt duplicate it. Then the gauge started moving from half to 3/4 back and forth on the way home. Also the heater is blowing cold air out and i was told thats a problem. Any ideas on why this car is doing this?
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  #2  
Old 05-25-2011, 10:08 AM
BMR_LVR's Avatar
BMR_LVR BMR_LVR is offline
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Location: Asheboro, NC
 
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Mein Auto: 1992 525i
There could be a lot of reasons. The cold air out of the vents indicates that the coolant system was likely not fully and correctly bled. Your problems could also be a clogged radiator or failed water pump. There are other possibilities as well including a blown head gasket.

Since your temp gauge went all the way to the red, I would strongly recommend you rule out a blown head gasket with a compression test or other reliable method. If the HG is good, then it would be highly recommended that you do a complete coolant system overhaul. This can be done as a DIY without a lot of difficulty. Quality parts will run $600-700.

Make sure you get this straightened out before you drive the car again or you may totally ruin the engine. They are very susceptible to blown HG's and cracked heads if they overheat. There is a lot of information here on the forum. I even had a thread from the time I overhauled my coolant system. Learn how to use the search function and do some research to help guide you.

Good luck

Steve
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It's Deja Poo - as in, I've heard this **** before.
Steve

Calypso Red 1992 525i with 200K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold

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  #3  
Old 05-25-2011, 11:36 AM
bladex10 bladex10 is offline
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When bleeding, do you take the bleed screw completely off or just unscrew it alittle?

Its just weird that the car can drive 25-30 miles with no problems at all, temp half way the whole time then out of nowhere start bouncing around. It doesnt spike up anymore. It comes and goes it seems and cant find out where the coolant leaked out from yesterday.
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  #4  
Old 05-25-2011, 03:38 PM
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BMR_LVR BMR_LVR is offline
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Mein Auto: 1992 525i
You have to make sure that the heater is on full heat when you bleed it. It can help to have the front end of the car elevated 6-12 inches. You don't have to completely remove the bleed screw.

You should not be loosing coolant. You must find the leak and resolve it.

I recommend that you purchase a hard copy of the Bentley manual or download the PDF format of it. It will assist you greatly.

Steve
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Most problems are usually something simple !

Quote:
Originally Posted by noego View Post
It's Deja Poo - as in, I've heard this **** before.
Steve

Calypso Red 1992 525i with 200K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold

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  #5  
Old 05-25-2011, 04:20 PM
robertobaggio20 robertobaggio20 is offline
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Dump a can of cheap green luminescent coolant into your radiator immediately. That's like $4 from walmart. It will be easier to spot the leak in your car.

IMO, you do need to remove the bleed screw completely when bleeding the radiator. I remove it totally, pour coolant till it flows out, start the engine, let the engine warm up to operating temp (cabin heaters on at max), rev the engine 2-3 times by snapping the throttle linkage open and shut, then add more coolant till no more bubbles are seen, then begin screwing the bleed screw in while adding more coolant and having it run out of the bleed screw's hole, then screw it in, top up the expansion tank to full, then screw the cap in and tighten with a rag wrapped around.

You MUST find that leak. My money is on your water pump's seal. Its buggy.

The time has come for you to replace the fan clutch, water pump, upper and lower radiator hoses (especially if they are hard to the touch), and the main cooling system hose that's under the intake manifold and looks like the arms of an octopus. This last hose involves removing the intake manifold, which is very time consuming, so use the opportunity to also change out your crankshaft position sensor and your camshaft position sensor. Remove and clean out your idle control valve, its just under the intake manifold and is easily seen when the manifold is removed. If you are so minded, dismantle your started and have it rebuilt - worth the money. Change the o-ring and plastic fitting that's under intake manifold just behind the throttle body. Get new vacuum hoses x2 (one connects to the fuel pressure regulator, the other connects to the valve cover near the front of the engine. Get new fuel hoses for the fuel rail, both at the front of the engine and the rear at the fuel pressure regulator. If you really have alot of time and money on your hands, purchase the beisan vanos overhaul kit for just under $100 shipped, dismantle your vanos unit, and overhaul it too. This will enhance your car's performance for sure.

While you're at it, change the electrical relays for your fuel pump, o2 sensor, dme and abs unit. Clean out your fuel filter, and if there's still more cash left over, purchase a new oem fuel pump and install it immediately, keeping the old one as a working spare.

All of the above would pretty much eliminate the more common no start situations for our car. Of course, clean out your air filter or get a new one, and use carb cleaner to clean your throttle body off all accumulated carbon. Remove your crankcase ventilation hoses and spray carb cleaner down it and any plastic hose fittings, to clean any crud off those as well. Its also not such a very bad idea to purchase brand new coolant temperature sensors, there are two fitted to the cylinder head under the intake manifold.

Revamp your car ! Why not. Why not? And yes.....do that compression test to rule out your HG first. Purchase the compression testing gauge and record your figures.

p.s. label all wiring switches carefully and make sure you fit the right stuff back together during reassembly. Not doing so will cause irritation error codes to appear later and your car and your engine will perform badly.
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  #6  
Old 05-25-2011, 09:56 PM
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luckydog luckydog is offline
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I have read that the radiator cap is designed to release overflow/overheating of coolant in the expansion tank . Since you did work on the thermostat . It sounds like a trapped air pocket ,or hydro locked where the coolant is not circulating. Right behind the thermostat top just enough air to lose prime . Possibility of air getting past the orange or red housing gasket The Orange gaskets are far superior to the red . Did you replace the housing too. These engines can be a nightmare to bleed the air out of the head ,there are various ways and tricks. It can take a week for it all to work out. I heard some Mechs have a type of purge vac that draws up circulation allowing the trapped air to escape. If all else fails pull the thermostat and watch the air bleed system process work right. Then once you find a reliable way to remove the air try installing the thermostat again in the car and use the one with the sm hole off to the side .
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Last edited by luckydog; 05-27-2011 at 08:53 PM.
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  #7  
Old 05-26-2011, 10:56 PM
japbike736 japbike736 is offline
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Mein Auto: 1990 535i, 1999 911
I had the same problem. The car would overheat on a short trip, cool down to near normal and then leave a puddle. It turned out to be low on coolant. I purged the system more than once. Followed the Bently to the letter. Didn't matter , it still overheated.......This may sound crazy but here is how I filled the block....I pulled the t-stat housing, pulled the t-stat, put the housing back on without the thermostat and poured coolant into the radiator hose untill it ran out of the radiator...It worked. No more overflow. Gauge stayed between 1/2 and 3/4 but it never went into the red, dependable again after that.
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  #8  
Old 05-27-2011, 03:18 AM
robertobaggio20 robertobaggio20 is offline
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Quote:
Originally Posted by japbike736 View Post
I had the same problem. The car would overheat on a short trip, cool down to near normal and then leave a puddle. It turned out to be low on coolant. I purged the system more than once. Followed the Bently to the letter. Didn't matter , it still overheated.......This may sound crazy but here is how I filled the block....I pulled the t-stat housing, pulled the t-stat, put the housing back on without the thermostat and poured coolant into the radiator hose untill it ran out of the radiator...It worked. No more overflow. Gauge stayed between 1/2 and 3/4 but it never went into the red, dependable again after that.
Your gauge is not supposed to stay between 1/2 and 3/4. It should either be a tad before 1/2, exactly at 1/2, or a tad after 1/2. A tad. That's it. Anything else and there is a problem.

Clearly in your case you had a busted thermostat. I suggest you get that fixed. If your engine is not in its optimal range, it will not give you optimal performance.
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  #9  
Old 05-27-2011, 06:43 PM
japbike736 japbike736 is offline
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Location: Pismo Beach, CA
 
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Mein Auto: 1990 535i, 1999 911
I had other issues. I replaced my clutch fan with an electric setup from Jeg's High Performance . That and a new thermostat cured all of my overheating problems. I can sit in 110 degree Vegas gridlock with the a/c on max for as long as I need to and never get over the half way mark on the gauge.

Last edited by japbike736; 05-27-2011 at 06:44 PM.
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  #10  
Old 05-28-2011, 07:29 AM
oldrotors oldrotors is offline
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Mein Auto: 1991 E34
Depending on what year your 525 is, there is a multi-outlet cooling hose that runs under the intake manifold and very hard to see (also a bear to change). Had it happen to me much the same, coolent underneath and not apparent where it was leaking. Check there could be your problem if its original.
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  #11  
Old 05-28-2011, 10:17 AM
robertobaggio20 robertobaggio20 is offline
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Its interesting that we've had zero feedback from the op (original poster), despite this many responses. I wonder if he's alright.
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