What is the maximum allowable oil pressure?

Hi there,

What is the maximum allowable oil pressure? (1.9 liter, 75 hp, diesel engine, type code: AAZ)

I'd also be interested in information about comparable TDI engines if you have any, as I don't know much about them. According to my gauge, the oil pressure rises easily above 7 bar when the engine is cold.

From what point does the oil pressure limiter start to regulate? Where is it located (in the oil pump?) and how can you tell if it's defective? How can you replace it?


Es interessiert mich eigentlich erst seitdem ich morgens Probleme nach dem Kaltstart habe, ich meine besonders an kälteren Tagen. Er springt normal an und läuft rund, geb ich aber dann Gas (auch Leerlauf) fängt er an zu stottern, hinten kommt Graurauch raus (ich nehme an nicht entzündeter Diesel). Zu Anfang merkte man es mitunter durch einen kurzen Leistungsverlust bei ca. 2000 U/min, was sich nach wenigen Hundert Metern auch gegeben hat. Jemand sagte mir es könnte an zu hohem Öldruck liegen der die Hydrostössel in der Funktion beeinflusst. Was Is it still a possibility?

It starts normally within a maximum of 30 seconds. The glow plugs are working, and the pre-glow and post-glow functions are operational. The timing belt has been replaced at 7,000 km, and the head gasket is new. It doesn't consume water and uses very little oil. If the engine has already been started that day, the problem doesn't reappear.

Engine oil pressure at cold temperature: Reading: 3 bar, when accelerating: above 7 bar. (Engine has been off for 2 hours).
Engine oil pressure: Warm engine - reading: 1 bar; Acceleration/Driving: 2 bar or more, depending on RPM.
Measured at the cylinder head.

I can only tell you the values when the engine is completely cold tomorrow morning.

Stukov wrote:

Oil pressure, cold engine: Reading: 3 bar, when accelerating: above 7 bar. (Engine has been off for 2 hours). Engine oil pressure: Warm engine - reading: 1 bar; Acceleration/Driving: 2 bar or more, depending on RPM. Measured at the cylinder head.

Hi,

"These values seem familiar to me. My Jetta has similar readings, and in that car, the cold start value is 2000 RPM at 8 bar."
I cannot provide you with other values because my TDI does not have dynamic oil pressure control.

Hello,

The pressure relief valve is located in the oil pump cover and should open at a pressure of 5.7 to 6.7 bar.
I would still consider a pressure of around 7 bar to be acceptable (these values apply to engine oil that is warmed up to 80°C).

The minimum oil pressure, even at 80°C and a minimum of 2000 RPM, is approximately 2 bar above atmospheric pressure for the AAZ engine as well.

PS: Measurement errors can vary depending on the measuring instruments used.

And what do you think about the hydraulic lifter theory? And what happens if I exceed the 7-bar limit with cold oil, so that we can assume values of 8, 9, or even more bars? (The gauge only goes up to 7 bar and isn't the most expensive one.)

Stukov wrote:

And what do you think about the hydraulic lifter theory, and what if I exceed the 7 bar limit with cold oil to such an extent that we can assume values of 8, 9, or even more? (The gauge only goes up to 7 bar and isn't the most expensive one.)

Hi,

"So, what interesting parallels: My Golf2 with a 1.8-liter engine and 90 horsepower also had extreme jerking issues – but even after replacing two oil pumps and a set of hydraulic lifters, the jerking persisted. Sometimes it would stall after just a few hundred meters from a cold start (overfueled). Supposedly, the high oil pressure was responsible for this. To this day, I don't believe that."

@Michael

kannst du mich vom Gegenteil überzeugen?


P.S.: I unfortunately sold the car with that issue, knowing it was faulty – I had several exams to prepare for at the time and didn't have the time to deal with it.

Hello Stukov,

Quote:

und was ist wenn ich bei kaltem Öl die 7 bar Grenze brachial durchbreche so dass man auch von 8, 9 oder mehr bar ausgehen kann?

That's precisely why the target values are also specified for warm oil (80°C). These values can already be reached with cold oil.

The engine reaches the target values, but I'm concerned about the symptoms mentioned, which only occur when the engine is absolutely cold and only for the first 30 seconds. That's why my question is whether this can affect the engine to such an extent.

This morning, he didn't cause any problems (as expected, now that the oil pressure gauge is installed). He started normally and ran as usual. The oil pressure was actually lower than I would have expected, at 1 bar when idling, while it later rises to 3 bar and then drops back down to 1 bar when at operating temperature.

I was just waiting to see if it would happen again, but based on the values I measured today, it's nowhere near exceeding the 7-bar limit with a brief acceleration after starting the engine.

What else could be causing this? Faulty fuel injectors? What about glow plugs? (maybe melted or something?). The fuel injection pump? (but why only for the first few seconds then?).

I don't see any air bubbles in the diesel line, I'm using regular diesel, and the diesel filter is new.

Okay, I'm adding to this discussion: Since installing a turbocharger in my car, I've installed an oil pressure gauge and have been monitoring it regularly. For the entire time, the gauge showed approximately 5 bar of oil pressure at idle when cold, and about 1.3 bar when warm. Under load, it would go up to the maximum reading (8 bar) when cold, and reach around 4-5 bar with a warm engine. However, for the past few days, I've noticed that the gauge is already hitting the maximum reading at idle when cold (approximately 8 bar). When the engine is warm, it does drop down to the usual value, but under load, it goes back up towards the maximum: starting around 2,000 RPM (even with only a slight amount of boost and load), the needle starts to fluctuate around 5 bar, and then quickly jumps to the maximum reading, where it stays.

Now I'm wondering if a) the instrument is faulty or b) my oil pressure is too high. So far, I haven't read much about the symptom of 'high oil pressure'; low oil pressure seems to be more dangerous. What could cause high oil pressure? What should I do and check? How can I test the instrument, if necessary?

The sender is located between the oil cooler and the oil filter flange using a RAID adapter ring.

'I have a VDO gauge that measures up to 5 bar. When the engine is cold, it seems like the needle is hitting the maximum reading. Therefore, I can't really tell what the oil pressure is when the engine is cold and idling. When the oil is warm, I get just over 1 bar at idle. At 2000 RPM, it's around 2.5 bar. However, in the summer when the oil gets very hot, I only get slightly less than 1 bar at idle. That's why I'm considering removing the heat exchanger and installing an oil cooler.'Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

Or use a different type of oil. What are you currently using?

Hello,
I use a standard pump-injector oil with a viscosity of 5W40. I change it every 15,000 km.

Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

I'm using a specialized 10W-60 oil in the summer, based on recommendations from the manufacturer of the installed hardware and due to the engine tuning. After the oil change (from 5W-40), it was noticeable that the overall oil pressure was slightly higher than before, but this behavior has only started recently and not since switching to this 10W-60 oil.

@ RTDI Tom
Have you ever replaced the oil filter to see if it's clogged and only allowing pressure relief through the spring-loaded pressure valve? Is that possible?

teileklaus wrote:

@ RTDI Tom Hast du mal den Öl- Filter erneuert ob der Zu ist und nur über den Federdruckbelasteten Überdruck läuft? ist das möglich?

Shhh! Don't tell anyone. The ARL has a bypass oil filter. It uses open-element filters, and those don't have an overpressure bypass. }

That's what you see with a professional thief – Bertil: Lesson learned .

What else would my engine do if, for whatever reason (what are the possible causes?), there is excessive oil pressure? Apparently, there isn't a pressure relief valve in the oil filter itself. Is there another one somewhere on the ARL engine?