Oil pressure woes - help needed

[Lorin]

Currently in Hungary having completed a 10 day offroad tour with World 4x4 in Croatia and now have a slight oil pressure issue.....

2 days ago whilst going up a hill in 3rd gear the oil pressure dropped off the gauge. Stopped, found oil level was low (will tackle the oil burning issue and blue smoke when I get home!), so I topped up the oil to the correct level.

Now the oil pressure is low - never getting much higher than the first marker and doesn't respond to the engine being revved which it previously did (pressure increasing with engine revs and then dropping when revs reduced). Also, when I turn the engine off the oil pressure gauge does not just drop to 0, instead taking a while for the pressure to drop....

My thoughts are that the oil pressure sensor may simply be playing up as the engine is otherwise running fine. Any thoughts/ideas/advice would be greatly appreciated.

 

[Chris]

Does the oil pressure light go off quickly on start up? The gauges are notoriously crap. I have swapped mine, messed around behind the dash etc and I can't get it to work. As someone said to me, if it didn't have a gauge you would never even give it thought. The second you have a gauge you start watching it. My new car doesn't have a temp gauge. It's blue at start up then goes out. That's it. I guess that if it gets too hot it'll come on red.

Chris

 

[Lorin]

Does the oil pressure light go off quickly on start up?

Didn't even know I had an oil pressure light so I guess it does

Cheers Chris, you're the second person to tell me to ignore the gauge so I'l take the advice and just keep an eye on oil levels etc.

Had me worried for a bit though.......

I will post a full write-up of the tour when I get back

 

[Chris]

Well, it's maybe not 'ignore the gauge' that I am saying but they are incredibly fickle and you had a low oil incident. There is a chance that this is enough to tip a crappy sender over the edge. I bought one last week from Milner for £20. I shall see if it works, but I think the problem lies somewhere else. it's a lot easier to swap incidentally if you pull the oil filter first. You can get to the sender really easily then. If the oil stays up and it's running smoothly and well and the lights goes straight out on the dash then it's probably fine. There is an oil level sensor on the side of the oil pan, and an oil pressure light too.

Now you've got me doubting that there is a light


Chris

 

[Lorin]

Cheers Chris, much appreciated

I am going to try and find a Toyota garage and maybe get the sensor changed. Otherwise will just keep an eye on things and and sort it when I get back.

 

[Paul]

In places like that you will have no worries in getting pressure checked at most local garages, not sure what it should be though.
You could always try agricultural dealers if stuck.

 

[Chris]

I had to go and check! The low pressure light comes on in the event of low pressure, but it's not illuminated as far as I know before start up. I actually had to read the manual.

Chris

 

[frank rabbets]

Is the low pressure light controlled by the same hopeless sensor that controls the gauge. Hope so. So you may still be OK.

Frank

 

[Chris]

I don't think it is Frank. I think it's a separate sensor on the engine somewhere. I was looking at the diagrams to try and fathom how it all worked and there is an oil pressure 'switch' available as a part I know cos I ordered one thinking it was the gauge
But they may all be interconnected. If I stick 12v across the back of the needle on the dash, it works perfectly. I have swapped the sender in the past for a used one and got the same result at the needle. So now I have a new sender, I shall stick that on and work backwards. My old one used to work fine. Clearly (he says) the gauge sends a variable voltage to the terminals on the instrument, based on the pressure of the oil inside the sender. There is then, the opportunity for mechanical failure and electrical failure. It's doubtful that the oil way would be blocked I would think. Worth getting a tester screwed in there at some point to see what good looks like. I did read what the pressure range should be somewhere. I'd just really like to crack it.

There are two wires to the sender. I can only presume that one is a straight 12v in and the other is the resulting voltage coming back out? So if you have a problem sending it 12v then you aren't' going to get a reading back out are you. Thoughts?

Chris

 

[frank rabbets]

I had a quick look at all the wiring diagrams but could not find the relevant parts. I think a mechanical gauge should be used just to test everything is OK. I'll try and find out what the running pressure should be. Is yours a diesel? If so I doubt whether you've done any damage as any play in the bearings usually ends with a loud knocking.

Frank

 

[frank rabbets]

Chris; I've had a look at the Toyota HDJ80 official workshop manual which I have a pdf for and on page 1025 there is a wiring diagram showing the low oil pressure warning light in parallel with the oil pressure gauge. Both are fed from a live feed and their wires converge to a single wire which then goes to the "oil pressure sender" then to earth.

In my 1995 24 valve vx owners handbook and on the car with the ignition on I can see a low oil level warning light shown as the outline of an oil can with a ripple underneath. Also in the owners handbook I can see a low pressure warning light which is just shown as an oil can with no ripple underneath. I cannot see this on the car with the ignition on. In the 'book it says this light might flicker at idle but if it goes out when the engine is revved then it is OK.

Lorin; Did you top up with a thinner grade of oil?

Frank

 

[Chris]

...and I found the test procedure for the sender unit and the dial. Will be tearing into that tomorrow. 'cos Sunday is Mud Day!

See what else I can bash.

Cheers Frank. I'll give that a look too

 

[adrianr]

I'd test with separate gauge and if you want an accurate ongoing measure an aftermarket gauge would be best...

 

[Chris]

I know that this was Lorin's thread - but it is all relevant to oil pressure. I don't want an accurate oil gauge particularly, I simply hate things that don't work. It's a Toyota. I swapped the sender today and did the test in the manual. You ground the clip on connector and turn the key. Yep, the needle went right off the scale. So there is continuity etc. Started it up and the needle crept to the bottom of the dial.

Hey, maybe I don't actually have any oil pressure?

Chris

 

[frank rabbets]

Hi Chris
I think just because the system checks out OK it does not tell you accurate oil pressure.

I have pdf on RME437E TOYOTA MANUAL for 1hd-td. On page EG 193 it says to check oil pressure by removing sender and fitting [Accurate!] mechanical gauge. Pressures HOT should be;

4.3 p.s.i. 600 rpm hot.
36-87 p.s.i. 3000 rpm hot.

There is no adjustment that I know of, but there is a pressure relief valve on the side of the block. The spring can go weak leading to low pressure.

Off to do mine now!!

Frank

 

[Chris]

That's interesting Frank. Would you post a quick write up of that once you've done?

I am a trifle concerned now that I actually DO have low oil pressure. The dial works, the sender is new and yet, there is barely anything on the gauge. The difference between bottom of the gauge and the middle (I know it's only an indicator) might only be a couple of psi. If you take account of the data you posted 4.3 to nearly 90 covers about 15 degrees on the needle.

I'd just like to get to the bottom of it really.

Chris

 

[Andy]

Do what I did & fit an aftermarket gauge, using a tee into the block where the sender goes, so I have both!

The after market one goes up & down with the revs wheras the one in the dash stays pretty much static.

 

[frank rabbets]

Results!! I used one of the three gauges off my airline which all read the same.

25 p.s.i. 600 rpm
70 p.s.i. 3000 rpm

I think 4.3 p.s.i. at 600 rpm must be a minimum.

Mine is 1995 24 valve diesel.

The engine was not as hot as on a Mway perhaps. I idled it for 20 mins and the water temperature gauge was almost up to where it is on a Mway. From past experience with other makes of engine worn bearings don't affect the pressure much. There is usually overkill capacity in the pump and most oil goes through the pressure relief valve with a healthy engine. I did notice that the terminals on the sender were a bit corroded but my dash gauge has always read quite healthy. You will need a 14 mm open ended spanner cranked at about 45 degrees to undo the sender. It was not very tight having a tapered thread. Some oil comes out so a tray under helps.

I would go for the relief valve if you have low pressure. My friend rebuilt an Aston engine and had no oil pressure. The relief valve plunger had not seated properly; then we had the wrong spring but all OK now. Sometimes it pays to radius the piston. If it is sharp on the end/edge it can catch the bore and stick open.

Let us know.

Frank

 

[Chris]

I was rather hoping for some info on the relief valve. As I posted, I have swapped the sender already. But yours is a 24v so not really going to be the same is it.

C

 

[frank rabbets]

I wouldn't be surprised if the bottom end of the 12v + 24v were very similar, together with the oil pressure readings. Anyway if you check with a mechanical gauge you will know where you are. Most engines run around these sort of pressures even non Toyota ones. Readings on my Morris Minor were the same!!

Good luck

Frank