Engine Oil Flush?

[KitsonRis]

Semi Clio related-ish as it relates to engine care, but the oil pressure light on my E34 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. Have seen a few posts online of other owners doing the same.

 

[oilman]

I would defidefinitely look at the pressure sensor. Oil wise, I would be tempted to go for a 5w-40 over a 10w-40 as they are the same when hot but a 5w will flow a bit better than a 10w on start up.

If you plan to use a flush, make sure you use a detergnt based one and not a solvent based one. The Millers and Castrol engine flushes are both detergent based.

Cheers,

Guy

 

[gez 172]

As above - drop down to a 5W instead of the 10W. See if that improves how quickly the light goes out.

 

[KitsonRis]

Yep, found the sensor I need and that so will check if it is leaking and the wiring. Doing more googling about it it is a poor placement of the sensor and the other end of the engine so does take time to read and most people are seeing the pressure light staying on for about 5 seconds.

Will also drop down to 5W-40 then. And thanks for the heads up on the flushes, never used one or looked at them so yeah. I can imagine this info beinbg Clio related seeing as a lot are now being stood for a while!

 

[JackJack]

I used a millers flush on mine as it hadn't been run for 6 months, hasn't blown up yet.

 

[NBG182]

I'd echo the above regarding trying some 5w. My van allows for both 5w40 and 10w40, but it sounds properly rattly on the 10w until it builds oil pressure - especially in the winter. Swapping over to 5w made it start much nicer.

 

[Robbie Corbett]

Also get a gauge in it - there's no guessing then.

 

[Robbie Corbett]

Just to add, I've also used a diesel oil in the past as they often have larger amounts of detergent additives, I did this with the M52 in my 328i and over 2 oil changes it made a significant difference to the tarnish and sludge around the valve train.

The diesel oil became dirty/black very quickly - think I changed after 1000 miles, after two similar changes I went back to my normal Castrol Edge and it stayed cleaner for far longer - to me this signified that the detergent in the diesel oil had indeed done some spring cleaning. This was at around 160k, I ran that car to just under 200k without issue.

 

[KitsonRis]

Just to add, I've also used a diesel oil in the past as they often have larger amounts of detergent additives, I did this with the M52 in my 328i and over 2 oil changes it made a significant difference to the tarnish and sludge around the valve train.

The diesel oil became dirty/black very quickly - think I changed after 1000 miles, after two similar changes I went back to my normal Castrol Edge and it stayed cleaner for far longer - to me this signified that the detergent in the diesel oil had indeed done some spring cleaning. This was at around 160k, I ran that car to just under 200k without issue.

So you used the same weight deisel oil for a small amount of time to help clean it then removed it and used the 'correct' oil?

A pressure gauge would be good, but don't want to be spending much money on it as it is meant to be for sale.

Have ordered a pressure sensor from BMW so will get that fitted along with an oil flush and 5W40 oil.

 

[npt]

Put in a quarter gallon of diesel in the engine and run for 30mins, that will clean the engine out, that's what you do to marine diesels prior to strip down

 

[R3k1355]

Can of oil flush helped out an old Polo my mate had. Used to flick the oil light on very occasionally, stopped after a flush. Deffo some crap in the engine somewhere.

 

[JamesBryan]

Might be alright on other engines, but engine cleaners on F4R's tend to wash away the crud inside that's keeping them quiet and alive 😂

 

[KitsonRis]

Might be alright on other engines, but engine cleaners on F4R's tend to wash away the crud inside that's keeping them quiet and alive 😂

I had similar with my old Octavia vRS when I had that TerraCleaned. Soon developed an oil leak that no one could find. Must have been during the cleaning process it got rid of some crud that was plugging a small gap.

 

[Robbie Corbett]

I had similar with my old Octavia vRS when I had that TerraCleaned. Soon developed an oil leak that no one could find. Must have been during the cleaning process it got rid of some crud that was plugging a small gap.

If no one could find it likely something super gash like the rear main. I think thats why the diesel oil was suggested to me, it gradually removes the crud with oil at the correct viscosity while the thin flushes can dislodge a wadge of shite which blocks the pickup etc.

 

[Robbie Corbett]

Also - why are you selling the 34? The be cool old tubs.

 

[KitsonRis]

Also - why are you selling the 34? The be cool old tubs.

Trying to buy a house. The houses I can afford don’t have big enough garages and it’s a car that I’m not keeping outside. I’m trying to work out some way of keeping it as it forms a large chunk of the deposit

 

[Robbie Corbett]

Trying to buy a house. The houses I can afford don’t have big enough garages and it’s a car that I’m not keeping outside. I’m trying to work out some way of keeping it as it forms a large chunk of the deposit

Well, hope you work out some way to keep it, nice ones are getting really hard to find