Question
Evan, Thank for your help with the question below on my 1999 build BMW 740 4.4 a few months ago. You were spot on with your answer and the car is now running fine.
I have one minor problem which I thought that you may be able to help with.
When using the wipers on rain senor/intermittant sometimes they will suddenly stop working and will not even work on normal wipe settings, the only cure is to stop the car and switch off the engine, once you restart the wipers work normally again. The wipers will work for hours in any of the continous wipe settings with out any problems.
Thanks
Steve
This is my orginal question below which you fixed
My 1999 build BMW 740 4.4 has the engine management amber light on. It is running fine. Orginally the fault was shown as electrical thermostat short to B+. The thermostat has been replaced and now the fault codes show faults 160,27,28. Please could you help my local BMW garage told me that it could be a fauly oxygen sensor and or an air leak caused by a fauly engine breather return valve which means stripping the engine and removing manifolds etc.
Any help you can provide will be much apreciated
Thanks
Steve
-----Answer-----
Steve, your repair facility is correct in replacing the Map Thermostat which can cause a check engine light. The shop is also correct in saying that faults 27 & 28 can be a faulty PCV valve (breather return valve). Tell them to Crack open the oil filler cap just barely with the engine idleing. The engine will make a whistling or honking noise if the valve is bad. It could also mean intake manifold gaskets leaking, throttle body gasket, or intake duct leaking. Those faults are lean mixture faults at idle. If the intake manifold comes off have them replace ALL the intake manifold gaskets and intake PCV backing plate. If the coolant valley plate has the black plastic cover on it, also replace that with the rear coolant crossover gaskets and O-rings. Doing this will save you future coolant headaches although it will cost you more to perform. Front O2 sensors should be replaced at 100,000 miles along with spark plugs. Sounds like your shop has a beat on this one.
-Evan
AnswerSteve, please replace the rain sensor and the wiper double relay in the electronics box in the engine bay. Make sure the optical element in the windshield isn't delaminating or have bubbles in it. The rain sensor is behind the rear view mirror plastic cover. Carefully seperate the plastic cover and remove. The rain sensor is the square plastic box with the four wire connector below the mirror there are two plastic tabs that you have to push up to remove the sensor. You will see what I mean when you look at the new one. Relay replacement is straight forward.
61 35 6 904 012 Rain sensor (part number may be superceded)
61 36 8 384 505 Wiper relay
The relay may be two relays instead of one depending on production.
-Evan
