question Low oil pressure at low rpm on zetor 7245

Hi,
I just did service on my new zetor 7245. I’ve changed all the filters, cleaned out the centrifugal filter and changed engine oil to 10w40.
This went fine, the tractor started and I could use it form some light tasks, but after using it at around 1000-1500 rpm for about 2 hours the oil pressure light went on..
There is noe issue when the engine is cold, however at around 100° the issue starts, at low rpm 500-700 I get the oil pressure light back.

Any ideas? I’ve already ordered a new oil pressure switch(?) just to rule that out.
Could it be the engine oil pump?
I’m really new to this type of machinery..

Hello Martin,

first - it would be nice if you post first a Hello, Iam martin, and this is my new Zetor 7245 (with pictures in best case). Thanks for.
You can do that here: Post thread - https://zetorworld.com/forums/hello_thats_me/post-thread

Bjellnd said:

Any ideas? I’ve already ordered a new oil pressure switch(?) just to rule that out.

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In most cases not the best idea.
Better would be to buy a oil pressure test set (like one from ebay for around 30 euros to messure the real oil pressure. like I do it here:

View: https://www.youtube.com/watch?v=XjziDeNKcD0
Good pressure will be betwenn 1,0 bar at low rpm (500) and up to 5,5 bar at high rpm (2.200).
If the light goeas on, its lower then 0,5 bar - and thats nothing you can work with. But the light goes out by around 0,7 bar and so you can think: hmm, its ok, the light is out. But it isnt - so, best practice is messure the pressure.

An often coming damage on older Zetor models with low oil pressure will be only a damaged rubber seal:

It is often enough to bend the pipe 32 a little so that it sits a little deeper in the blind hole with the sealing ring 33 and to put in a new sealing ring 33. It is best to have one with an oversize (originally it is 18x2 mm - better is 18x2.3 mm with a thicker cord) and made of Viton or silicone instead of NBR (which was originally installed at the factory).

When fitting the pipe 32, make sure that you do not pull it out of the blind hole when tightening the pipe. This is a somewhat unsightly construction in this place, but if you pay attention, it is not a problem.

And if you have already removed the oil pan, check that the mass balancing weights on the crankshaft (2 pieces) are firmly in place. On your model, these could have come loose over the years. I suspect it is due to the fact that the pulley on the crankshaft is often not balanced on these models. Subsequent models had a balanced pulley and loose mass balancing weights are rather unknown.

This problem applies to ALL Zetors from Zetor 2011 to Zetor 7245. From Zetor 7745 onwards there was a balanced pulley.


Most engines had great oil pressure again after this repair.

Alright, I guess the oil pump assembly you are referring to is located behind the oil pan?
I'll start by checking out everything you pointed out!
My local automotive store has an oil-pressure test kit that should work.

But what oil do you recommend? You seem to have a lot of experience! I forgot to mention that I'm using semi-synthetic.
Also, is there any point for swapping the oilpump?

Bjellnd said:

Alright, I guess the oil pump assembly you are referring to is located behind the oil pan?

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yes

its possible to use a 15W-40 diesel engine oil with the centrifugal oil filter - that should have no issus with oil pressure. A 10W-40 should work to.

Bjellnd said:

Also, is there any point for swapping the oilpump?

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Check the pipe and rubber seal first, if that is not the problem, check the engine oil pressure valve, and if thats not the problem, try to change the pump.
If the problem stays ... there can be a bigger problem such as damaged/worn crankshaft bearing shells.

Oh, that reminds me, if you open the bottom of the engine, make sure you check the axial bearings on the rear bearing of the crankshaft, they must be there and must not have too much play. If you stand on the clutch a lot, these axial bearing shells wear out and eventually the front one can fall out and then you have massive wear on the engine block and the crankshaft... then a total write-off is imminent.

But you can also check it from the outside:

simply try to move the crankshaft forwards and backwards on the pulley with a tire iron.

When the engine is open, you can do this even better directly on the crankshaft, it's easier that way.

If the longitudinal play is more than 2-2.5mm, you should replace the front two axial bearing shells, which can be done without removing the crankshaft and doesn't cost much.

Joachim said:

Good pressure will be betwenn 1,0 bar at low rpm (500) and up to 5,5 bar at high rpm (2.200).

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at engine temp 80-100 I get 3 bar at 1000 rpm. (The second the cooling water hit 100°) It moves with the rpm somewhat. “Max” is getting lower and lower.
Have been idling for an hour, but I can’t get the pressure above 2,2 bar

Ok, then look at the rubber sealing I wrote.

Joachim said:

Ok, then look at the rubber sealing I wrote.

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You might be correct
The oring on the right is the one you were suggesting that was bad. It’s crusty and very “hard”

There was about 1-1,5mm play in the crankshaft. From me eyeballing it

I’ve ordered a new gasket for the oil pan

Anything else I should check while I have it open?

Bjellnd said:

Anything else I should check while I have it open?

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I wrote that in my post above.

Bjellnd said:

The oring on the right is the one you were suggesting that was bad. It’s crusty and very “hard”

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typical for many years old NBR rubber - replace it with a viton or silicon seal with 0,3 mm more and have fun with a great again oil pressure.

Bjellnd said:

I’ve ordered a new gasket for the oil pan

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mount it right way... clean the metal and mount the paper gasket with both sides thin default grease (not graphit and not EP grease) on it

it did not seem to help.. I changed the oring to one you recommend.. but I still can’t get any higher pressure than 3bar at cold engine..

OK, that's not nice.

Then I would next have the pressure relief valve on the pump checked to make sure it doesn't open too early or let the oil through for a long time.
If that doesn't help either, you should take a closer look at the bearing shells on the crankshaft - there might not be any major damage there and the oil pressure would disappear.
If that doesn't help either, my next step would be to replace the engine lubricating oil pump...

Just to be sure, you are 100% sure that i should be able to get around 5,5 bar at high rpm? I cant find it in my workshop book or owners manual.. (i'm just curious).

The relief valve is the one i've marked on the picture below? (me asking dumb questions might help another newbie)

Bjellnd said:

i should be able to get around 5,5 bar at high rpm?

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Yes, around 5-5,5 bar

Bjellnd said:

I cant find it in my workshop book or owners manual .. (i'm just curious).

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group 07, picture 11 - there you can find it

Bjellnd said:

The relief valve is the one i've marked on the picture below?

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exactly

We all started somewhere and were beginners.

I checked with some local Zetor enthusiasts, and they recommended removing the centrifugal filter and converting it to a regular oil filter. I went ahead and did that. During the process, I noticed a second O-ring that was completely destroyed. This second O-ring, located behind the old oil filter, might have been the cause of the issue. Now i get up towards 5,5 bar

It is best to use O-rings made of silicone or Viton, they last much longer.