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KitsonRis

Oil Flush? Low pressure

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The oil pressure light on my E34 535i is slow to turn off when starting to the extent another warning appears saying oil is low but that then turns off after about 30-40sec of it starting. It was always been slow to turn the oil pressure light, I was assuming it was because it is such a big heavy lazy engine.
I checked the oil level and it is at the max mark on the dip stick so I am confident it has oil . It isn't leaking or antything.
Two thoughts - oil pressure sensor is on the way out or the oil pump is a bit clogged up as it is sat for long periods of time. Last had an oil change less than 2k miles ago back in August 2020, looking at the dip stick the oil is still clean.
Going to replace the oil and pressure sensor (if it is the on on the bottom of the sump that I can get to without removing the sump) to see if that helps, but is there anything I can also run through the engine like a flush/cleaner? I would be even consider putting some thinner oil in, running it for about a minute or two, draining that and then topping back up with correct oil (not sure if that is sensible. I don't mean like water thin oil, just a grade or two thinner kind of thing). Currently has 10w-40 fully synthetic oil in. Hoping a quick flush and clean though will help. The last time I had the car out was back in Sepetember and that was only briefly, last long run was in July/August so it could just be from lack of use. Or actually being an older style engine would running a slightly thinner oil in it be sensible? It is on 127k miles.

 

Does anyone have a part number for the oil pressure sensor? As I don't thinl 12611717394 Levelling switch is correct.

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48 minutes ago, sharkfan said:

Check the camshaft Banjo bolt?

I would hope not seeing as they were replaced the other year. But will give it a check though.

Is that just rocker cover off and nothing too bad? Will admit a garage replaced them at the same time they were painting engine parts so I never did it.

 

Also have ordered a genuine oil pressure switch from BMW, managed to find the right part number on RealOEM.

Edited by KitsonRis

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Plenty of youtube and picture links but yes, just the cam cover off to check. Good idea on the oil pressure switch as the smallest leak on them can set them off.

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Cool, will look at doing that then if it is just a simple removal of that.

 

That is what I thought, replace the simple cheap parts to start with.

 

Have seen and been suggested to use 5W40 oil to help this. But can't find this advise again relating to these engines so no idea if this is sensible. I also stand corrected by what oil I have in there, it is 10W40 semi synthetic oil as I found the old invoice.

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I never use fully synthetic oils in BMW engines of this era or earlier.  I appreciate everyone has their own opinion re oils but I have never had an issue with oil pressure and/or engine failure. I use either a good quality mineral oil or semi synthetic 10w40 like Mobil 2000 or similar.  I've found less leaks when sticking with mineral oils also. My personal preference is a mineral oil like the Motul 4T. 

 

https://www.autodoc.co.uk/motul/8820426?gadw=1&gclid=CjwKCAiAp8iMBhAqEiwAJb94zyUVeaguQeXO1dHKxEC7bXeQfpsxMQmqxtZdzJCVVwL-ulmLavsMNBoC3CcQAvD_BwE

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I also use a semi synth oil, usually a 10w/40, 5w/30 being too thin for these motors imo. 

 

Anyways... I would check the banjo bolts as a matter  of course, but it's unlikely they loose if not long done, but not impossible. Personally I would be looking closely at the oil filter housing assembly as particularly the early ones were known to develop an internal fault with the non return valve which allowed the oil to run back to the sump when the motor is at rest.

 

The pick up gauze in the sump could quite possibly be blocked but again unlikely if maintenance has been kept up. 

 

The sensor in the sump is for oil level, with the oil pressure sensor at the rear of the cylinder head on the intake side. Usually quite reliable but worth a visual check. If its leaking it will be obvious.

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On 09/11/2021 at 20:46, KitsonRis said:

a garage replaced them at the same time they were painting engine parts

 

What were they painting? Some silly sod once powder coated a cam cover - on both sides. Within 1000 miles the hot oil had taken most of the powder coat off the inside and out ended up in the oil pick up gauze.

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OIl filter housing for me as well, I am starting to see trouble in those over the last couple of years

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52 minutes ago, Tims said:

OIl filter housing for me as well, I am starting to see trouble in those over the last couple of years

 

Porus, or poorly installed/buggered seal?

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On 15/11/2021 at 17:36, Sir Anthony Regents-Park said:

 

What were they painting? Some silly sod once powder coated a cam cover - on both sides. Within 1000 miles the hot oil had taken most of the powder coat off the inside and out ended up in the oil pick up gauze.

They painted the rocker cover black to tidy it up a bit, should have got them to to the inlet manifold as well thinking about it. 
 

I have a genuine oil pressure sensor but it looks like it is going to be great fun to fit! I took a quick look the other day when I had a spare 5 mins and couldn’t even see it, presume it is hidden under the coolant reservoir and some other thing I need to remove? 
Engine flush, 10W40 semi-synthetic oil and filter is on order and due to be delivered later. Just need a dry day to roll it out the garage and sort it all out. 

Will look at the filter housing when the filter is out to see if there is anything. But I did look at that the other day and it wasn’t leaking out the seal. From what I can tell there are no leaks in it as the oil level is bang on. I have “regularly” changed the oil, last time was back in August 2020 but I haven’t done 3000miles in it since so sure that can’t be a problem? But it is being changed before it is used again. 
 

Just worried as the flush I have ordered says to put it in and run for 10-20mins then change the oil. But with a low pressure warning I don’t want to leave it running for too long but the warning does disappear after 40secs of it being turned on, so I assume it is just slow to build pressure (if the sensor is reading correct). 
 

I was doing some reading and the fact it is stood not being used for long periods of time can cause this. And I haven’t properly used it since about August maybe. 

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22 hours ago, sharkfan said:

 

Porus, or poorly installed/buggered seal?

 

 Non return valve not non returning

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See it alot more on B34's, by but as Paul Five-Oh say's, seeing it on B35's

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Small update. Have fitted a new oil pressure sensor. Turned it on the oil pressure light went out after what I remember a normal time and the dash warning didn’t come on. Currently has a bottle of Millers Engine Flush in while idling then I’m going to do an oil change. 
So fingers crossed it was a faulty sensor! 

I’ve got another day off next week so will take the rocker cover off and check the banjo bolts (don’t have time today but the car isn’t being used so it’s not the end of the world). 
 

If it is the sensor then I’ve fixed two of my cars this morning with a simple part swap in under an hour!! 

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