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Old 03-07-2011, 07:44 PM
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BMR_LVR BMR_LVR is offline
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Location: Asheboro, NC
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Mein Auto: 1992 525i
Mechanical things you need to know about your E34 - UPDATED 3/22/11

Stomp Test Procedure moved to top of list 3/22/11

Hello fellow Festers. This is a thread designed to be comprehensive in nature and assist current and new E34 owners with some of the common problem areas and failures of the E34. Please feel free to add to the list as I'm sure that I will not remember everything. I will update the original list accordingly. Of note, I will only plan to add things to the original post that are known problem/failure areas, preventative measures one can take and the recommended fixes that are universally accepted and recommended. Some have suggestions that are "unconventional" that they have had success with. There is a thread coming for those suggestions. This list is compiled from my years of owning BMWs as well as the experience of others who have basked in the glory of the mighty E34. There are some caveats with this list due to the varying models of the E34, but it should be a good list to cover most situations/models.

First things first ......... Obtain a copy of the Bentley manual. It is by far the most comprehensive repair manual for the E34. Here is a list of problems/failures that are common on the E34 and preventative measures.

Stomp Test Procedure

I decided to move the stomp test procedure to the top of the list. This is absolutely the first procedure that should be done to diagnose a problem (unless of course your radiator is puking coolant due to a busted hose or something obvious like that) Our BMW has a computer (OBD I - on board diagnostics I) that will store fault codes if it detects a problem with many of the components of the car. Per the Bentley manual, this works for 1992-1995 models only. This is one of the very first things that should be done if you experience driveability problems or if your check engine light (CEL) comes on. Many have asked how to perform the stomp test. I decided to create a thread dedicated to this procedure. Follow this link for the step by step procedure with the associated fault codes:

Cooling system

Do not let your engine overheat !!! This cannot be stressed enough. If it gets to the red zone, it is in danger of major damage including a blown head gasket and/or a cracked head. This is a very difficult DIY and very expensive if done by a mechanic. The E34's cooling systems is its Achilles heel.

- One may want to consider a complete cooling system overhaul every 100K miles or so. The best case scenario is replacement of the radiator, belts, hoses, pulleys, water pump, thermostat, thermostat housing, fan clutch, fan, radiator cap and bleed screw. Of note here, there is a special fan holding tool that is invaluable to removing the fan assembly. A 32 mm wrench is required for the large nut holding the fan clutch to the water pump shaft. This is a reverse threaded nut, so the wrench has to be turned clockwise to loosen the nut. The holding tool and wrench can be obtained online for about $30-$35. It is money well spent. Believe me, I know because I ruined a water pump pulley trying to use the inappropriate tools. A regular coolant system flush can help stave off some of the problems. A coolant system overhaul is not a difficult DIY on the E34. Please see post # 10 for two very good videos on the BMW coolant system (thanks Bluebee ) While the E34 is not listed, virtually every single thing in the videos apply. The only real difference is the location of the bleed screws. In fact, the radiator in the second video appears to actually be an E34 radiator.

- Some of the parts of the cooling system from the factory are made of plastic that, over time, will fail. The upper radiator neck is a common breakage point. The plastic bleed screw can fail/break easily. Be careful not to over tighten the bleed screw as it should not take a lot of torque to get it to seal. Brass replacement bleed screws are available that are very nice looking and will not break.

- If replacing the fan, it is universally recommended that you only use the oem fan as the aftermarket ones are of inadequate quality and are prone to breaking apart. The fan clutch is an item that can fail. When new (and the engine off and cold), the fan clutch turns like the internals of the clutch are like molasses. If it turns with virtually no resistance or it will hardly turn at all, then it is time to replace it.

- The factory water pump comes with a plastic impeller that over time will disintegrate and cause an overheat situation. There are water pumps available with a metal impeller as well as ones available with a composite impeller. It is a universally accepted recommendation that the plastic impeller water pump be replaced with the metal impeller water pump. There is also a high flow water pump that is pricey, but is reported to flow much more coolant. It is commonly used in racing situations. The thermostat housing is made of plastic and there are aftermarket aluminum housings available. The design of the thermostat housing is such that a sealant is not required if all mating surfaces are smooth, straight and properly cleaned. However, premium high temp thermostat gasket sealant can safely be used as an extra measure (thanks LD), just be sure to not use too much as it may get into the coolant system. The t-stat for the E34 comes in three different temperature ratings, 80, 88 and 92 degree Celsius. My recommendation would be to replace with the one that came in the car from the factory. Some opine that lower temp t-stats allow the engine to run cooler. Others say it only allows the engine to cool sooner because it opens at lower temps. Do your research as the jury is out on this one.

- BMW recommends its brand of coolant only, but it is pricey. Some suggest that you can safely use less expensive coolant that is green and has a sweet odor. This can aid in visual discoveries of leakage as well as being more apt to smell coolant if it is leaking. Many have had good experiences with the lesser expensive brands. There is a very detailed thread on this here :

- Many feel that bleeding the coolant system is as difficult as brain surgery, but if done according to the Bentley manual, it is not difficult and can be done in one to two bleeds. Of note, the 540 reportedly has a self-bleeding system. One key is to make sure your heater is on full hot and the fan is on maximum. You can also elevate the front end 6 inches or so to help the air move up and out of the system. A sign of a coolant system that has not been completely bled is an overheat situation in combination with no/little heat from the heater.

- If allowed to overheat, the head gasket can fail and/or the head can crack. If this happens, it is bad. Signs include an engine that continues to overheat and loose coolant despite topping off. Of course, if one just loses coolant, the one should examine the entire system for a leak. Other signs include milky looking oil, oil in the radiator, bubbles in the expansion tank when the engine is running and large amounts of steam coming from the exhaust pipe. A compression test and/or bleed down test are two of the more definitive tests for a blown head gasket and/or cracked head. The oil and coolant can also be sent off to be analyzed.

Fuel system

- The fuel system can present instant or insidious problems. Frequently a car will not crank well, be low on power, have severe hesitation or just suddenly quit. The best way to address the fuel system is in an orderly fashion. First check the simple things, i.e., make sure you have gas in the tank (sorry, but it happens). Next, check the fuel pump fuse. If bad, replace. If not proceed. If you have a can of starting fluid, squirt it in the air box for about 2 seconds. A word of caution here, the MAF has a wire that heats up and can potentially cause a fire with the starting fluid, but I think that is rare as hen's teeth. Anyway, if the car cranks and runs for a second or two, you have essentially narrowed the problem to a fuel delivery problem. If this is the case, then you need to proceed with a little more detailed diagnostic procedure.

- If the fuel filter has not been replaced in a long while, then you should replace it. BMW recommends that it be replaced every 30K miles. Some feel that they can be cleaned, but again, I am sticking with recommendations that are either recommended by BMW or universally agreed upon. Now you need to check to ensure that there is power to the fuel pump. This is accomplished with a multimeter and by jumping two terminals in the fuel pump relay socket (#30 and 87). Here are a few pictures of the jumper I made according to Bentley manual instructions.

- I will not go in to great details on the socket jumping procedure here because the information is here in this link kindly provided by Roberto (it's from the Bentley manual that is a must for E34 DIY'ers).

- If the fuel pump purrs when the sockets are jumped, then the fuel pump relay is bad. It is a very good idea to have a spare fuel pump relay with you at all times. If the car suddenly stops on you, you can simply replace the relay. If that is the problem, the voila, it is now fixed. If the fuel pump does not purr with the relay sockets jumped, then the pump is likely bad. It is possible that it is the wiring from the FP relay to the pump, but that is unlikely. Sometimes the pump is just weak and in early failure. This can be tested by checking the fuel pressure at the fuel rail. I am not very familiar with that process or the pressures that should be present. Someone please chime in here. Finally, the injectors may not be firing or may be clogged. They can be tested with a multimeter and there is a flushing and back-flushng procedure as in this video:


Thanks Roberto . It is very uncommon for the problem to be fuel injectors if there is a sudden no-start situation or if the car suddenly dies while driving it. The fuel pressure regulator can also be a problem, but it is not very common. Someone may be able to chime in with more information and I will add it here.

BMW factory radio code reset procedure. Here is a direct quote from the BMW anti-theft radio owner's manual:

"To enter your security code, which can be found on the two cards supplied to you by BMW, turn the radio on and use the appropriately numbered radio push-button selectors. If the correct code is not entered in three successive tries, the radio will not accept another entry until it has been left on for one hour.

Important: If you make a mistake in entering your code, complete the entire sequence before entering the correct code. For example, if you r code is 12345, and you mistakenly enter 125, finish the five-digit sequence (45) to complete that entry. The radio will not operate, and the wok "CODE" will again appear on the display. Enter the correct code this time.

Exception: IF you hear a beep when entering your code, stop immediately! Begin entering the code again, starting with the first digit."

More to come later

Most problems are usually something simple !

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

Calypso Red 1992 525i with 225K miles

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

Last edited by BMR_LVR; 03-22-2011 at 06:15 AM.
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