Low Oil Pressure and Top End Engine Tap

Hi all
I have a 1996 GQ 2.8 Turbo Diesel wagon. This problem started an intermittent one but it is getting worse. The oil pressure has dropped from being just under 4 on the gauge to just over 2 for normal running. There is also a tapping noise in the top end that also varies in severity. There is a oil leak that appears to be coming from the oil pump. At first I thought that it was the sump but I have re-sealed the sump and replaced the oil pressure regulator at the same time. Could the oil pressure regulator spring have broken causing this or can a gasket leak on the oil pump cause low pressure. Or worse case, could the oil pump be failing?

Thanks

Granny


A Bad Days Fishing Beats A Good Day At Work!

Hi Granny.
How many K's has she done?,If you have any kind of leak at the oil pump, the pressure will suffer.
Have you tried a separate oil pressure test, your sender or guage may be faulty.
I would remove and inspect the oil pump if a test confirms low oil pressure.
The tapping sound could be caused by a loose or broken cam shaft retaining bolt.
The oil pressure may fail at any time if you don't address the situation asap, costing you a full re build.

EDIT. If you have re sealed the sump because of an oil leak, it is probably coming from the front oil seal at the timing cover which requires removal of the harmonic balancer and timing belt sprocket.
A leaking front seal will not cause low oil pressure, unless you run out of oil.
There is a procedure for replacing the seal, so if you're not sure, ask here.
Cheers, the ferret.

My patrol has 198000 km in the clock. The engine tap and oil pressure problem occurred simultaneously so I assumed they are related. The oil leak does not use a lot of oil so low oil is not the problem. Could the engine tap be caused by a blocked oil gallery? If so can this be fixed with a high pressure engine flush? As for the oil pump, is there any tricks to taking this out of the engine and reinstalling it? One mechanic I have spoken to seemed to think that the oil pump is linked to the timing of the engine and is the oil pump gasket easy to replace?
Initially my main reason for joining the forum was to be able to download the repair manual do that I could have a look at how things were put together. The other reason was to be able to get advice from other users who knew a bit more about what they were talking about. I am fairly comfortable working on a petrol motor but diesels are a bit different.
Any help I get is appreciated.
Granny

Also when I re sealed the sump I checked the main seal and it was fine. The oil leak appears to be coming from the front right as you look in under the hood. I have not pulled the covers off yet for the reason that the harmonic balance needs to be removed.
Granny
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A Bad Days Fishing Beats A Good Day At Work!

Hey Granny, Best if you give the engine a good clean in the suspect area and watch to see where the leak is coming from.
Any oil leak from the front seal or sump, gets blown back along the motor by the fan.
Light tapping sounds come mostly from the tappets/valves.
I doubt if you have a blocked oil gallery.
A pressure flush won't help.
Using a length of hose about 1metre long, put one end to your ear and use the other end to find the source of the tapping noise,
Watch your fingers and the hose as as you play doctors or you may need to find a real doctor!
Also, some aftermarket oil filters can play havoc with oil pressure, so you really should get an oil pressure test done.
Cheers, the ferret.

On this motor where is the oil pressure sender located? Is it on the drivers side rear below the injectors?


A Bad Days Fishing Beats A Good Day At Work!

Pretty sure it is Granny, just below number 5 injector.
Behind the oil filter and towards the firewall.
You will need to remove the intercooler to get at it.
Cheers, the ferret.

Thanks for that.


A Bad Days Fishing Beats A Good Day At Work!

Quote:

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Originally Posted by Granny

Thanks for that.


A Bad Days Fishing Beats A Good Day At Work!

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You can remove it and put a "T" in and fit a mechanical gauge as well as the original. the Nissan senders are not much chop.

When was the last oil and filter change? Oil may be getting a bit thin Too.


Tim

Like Ferret said, the oil senders on our rigs are not to be relied on. The tapping sound could be the lifters or it could also be an injector. Finly, I think you are referring to viscosity breakdown not actually thinning. With our indirect injection engines, oil tends to thicken with soot rather than thin.

also back up the comment about the filter above, have spoken with a few blokes that work on the TD42 Deisels "yes different motor" but they say that some aftermarket filters play havok with oil pressure readings and that genuine nissan filters are the only way to go. Even the bloke at the nissan parts counter told me that the aftermarket filters are way too high flow and the genuine ones are more restrictive, hence the better oil pressure reading. Would be nice if it was a simple fix for ya.

I think your best bet is to mechanically check the oil pressure. Remember, if your oil pressure is low, it more likely an indication of bearing wear or oil pump wear. Poor oil filters usually do not have an anti drain-back valve which operates properly. This allows the filter to empty of oil and delays the buildup of oil pressure on start-up. I have found Fleetguard to be real lousy filters. On the other hand Wix and Denso filters along with Nissan filters have worked very well for me in both rigs.

Thanks guys. I have been using ryco filters for the oil so i might get a Nissan one next time round. This change is 3000 km old and I will be changing it at 4000. The last oil change I did was at 2000. I have been using castrol rx super but I used valvoline super diesel on the last change. What is the best oil to use? I am open to suggestions. I think I may have found part of the problem. I was concerned that the engine seemed to be chugging with the noise coming from the air intake. I thought this had been changed in a service I had done but it would appear not. Taking the filter out quietened the engine down and the oil pressure rose to wear it would normally be but dropped as the engine warmed up. I don't know if it was because I could hear the turbo working but I felt there was more power when I took it for a drive. I will still get the oil pressure tested and a mechanical gauge installed but I may be lucky and the other symptoms could be filter related. Looks like a trip to the local Nissan dealer is on the cards. Unless someone knows a better supplier. Thanks for the help guy. I will give these options a go and see what happens. When I have givens Patrol a wash I will post up a pic as my avatar. Cheers


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A Bad Days Fishing Beats A Good Day At Work!

I have been leant an oil pressure check gauge. On the RD28T motor where will I find the sender unit?

Thank

Granny


A Bad Days Fishing Beats A Good Day At Work!

Driver side, engine block, below No 5 injector, between the oil filter and the firewall, take care when unplugging!!
Cheers, the ferret.

Thanks


A Bad Days Fishing Beats A Good Day At Work!