4A-GTE Oil Pressure Low

[Talasas]

Hi all

Okay I've got to bite the bullet and seek some advice for this one. Since I finished my GTE conversion earlier this year I've noticed my oil pressure guage reading low compared to what I used to get beforehand. Lately it's been getting somewhat worse and sometimes it drops a fair way down (according to the gauge) while other times it's in the acceptable range.

So here's the rundown of what I changed for the conversion:

- Turbo oil feed line where oil pressure sender was. The lines goes Block > 20cm braided line > T piece with sender > ~40 cm oil line to turbo.

- Larger oil cooler was added to replace the standard AE93 oil cooler.

- Oil pump was checked when engine was rebuilt, was in good order.

and here's what I've looked into:

- Overfillled with oil, I initially added a tiny more oil when filling to compensate for the amount that sat in the lines for the turbo feed/return and oil cooler. I checked this and drained some oil to make sure. No change.

- I read that sometimes for bush bearing turbos (mine's a CT9) a restrictor may need to be used in the oil feed line. At first I thought I'd try it without but since I got this issue I machined up a restrictor and added that into the line, taking it from 3.8 mm ID to 1.6 mm. No change.

- I noticed the oil pressure sender was single wire type so I assume that it earths on the block. I ran an earth line to the pressure sender temprarily to check if that's why. No change.

I'm starting to get concerned, when I have some more time this weekend I will take off my bumper and bypass the oil cooler to see if that's why I'm getting a pressure drop. I have my doubts though as cold idle pressure is low as well and the 4A-GE oil cooler doesn't open until the oil is hot.

Can anyone offer any more advice? I'd really rather not sieze my freshly rebuilt motor. It hasn't done many kms yeat but I need to drive it more and more as the year rolls on.

Apologies for the long spiel.

[30psi 4agte]

Have you changed the weight of the oil you run ?

What type of oil s it ?

What does the pressure drop too ?



FWIW My oil pressure is very low at idle...... Always has been though. It is about 5-10 psi if the revs realy drop.

Usualy sits just above 10psi at idle and 50-60 psi at revs. I do run large bearing clearence though.

P.S it is good that you put that restrictor in the line ! You can ruin turbos with over supply.

[lexsmaz]

You will need to hook up a master oil pressure gauge to know exactly what is happening, there is a Ryco brand available, just unscrew your oil pressure sender & screw this in they have multible fittings on the end, just pick the one that suits your thread .. Otherwise you are only guessing if you do or dont have a fault, factory gauges are only really just an indicator ...

[oldcorollas]

the old cooler was a bypass unit no? is the new unit full flow? (oh, using original take off device?)
you might need to take the above mentioned pressure gauge, and tap into various points, to see if you have any major pressure drops.

1.6mm may not be small enough for the restrictor, but it is probably no tlarge enough to be draining your oil pressure....

is it same engine? different engine with bigger bearing clearances?

[Talasas]

Same engine with new bearings and pistons and rings, the clearances as far as I know should be standard spec as I asked the bearings to be replaced as needed. I'm not too certain about the oil cooler type, I had a larger flatter one here at home and replaced the short fat one they fit from factory to give me more room. I'm using Castrol GTX Magnatec which is 10W40.

Okay I'll have to try and borrow and oil pressure tester from somewhere as I can't afford to spend the $90 on a pressure tester at this moment... anyone in Adelaide that can lend me one for a day?

[Talasas]

Okay, I dug through some of my gauges and tried out a couple of mechanical pressure gauges to see what they read. The readings were pretty consistent:

cold idle - 40psi @ 2000 rpm
warm idle - 35psi @ 900 rpm

and it jumps to about 50psi+ when I open up the throttle, it's hard to see the exact figures on the rev because I'm by myself ATM and I can't see the gauge when I reach for the throttle

Should I be concerned?

[30psi 4agte]

Hell no !!

Like i said im not even concerned with mine at idle and mine is just over 10psi.

yours is spot on at rpm too.

[Talasas]

Thanks, that's a relief. I really was not looking forward to having dismantle anything again. Thing is, with a lower idle pressure (like your 10psi say) is it enough to get oil up to the cams?

[30psi 4agte]

Yeah no probs there.

Pressure and flow are two different things..

[mrshin]

I presume your initial concern was coming from the factory oil gauge? Those things aren't exactly the pinnacle of consistancy/accuracy...

[Talasas]

I presume your initial concern was coming from the factory oil gauge? Those things aren't exactly the pinnacle of consistancy/accuracy...

Yes, and while that's true, my concern came from the large change shown by the factory gauge. Many things had changed during the conversion - why the gauge was showing something totally different was a little unsettling.

Anyway, you are right and I think I'll be looking into some aftermarket gauges soon. Are electric ones all plauged with possible unreliable readings? Because I'd used a mechanical one but there is a pressure drop over the long line I'd need to get it to the cabin...

[Talasas]

Oh and for anyone in future who finds this thread with the same concerns, I looked up the oil pressure specs in the 4AGE Engine Manual:

Under warm engine conditions:
At Idle: 4.3 psi (29 kPa, 0.3 kg/cm²) or more
At 3000 rpm: 36 - 71 psi (245 - 490 kPa, 2.5 - 5.0 kg/cm²)

[lexsmaz]

So long as you use the correct line & fittings that come with the mechanical gauge, pressure drop will not be a problem, the only problem i worry about is if the line fails / splits inside the cabin !!! but again if its all done ok, ie; Nothing sharp etc near the line you will be ok & remember to put a rubber grommet on the line were it goes through the firewall ...

[BigWorm]

Best way to protect the thin plastic tube for mech. oil pressure guages is to run a rubber vacuum line over the whole length of it, but most importantly over the section that runs through the cabin.
That'll protect it from any random sharp edges or any pinching, & anything you run through the firewall should be running through a grommet, always!

[LeeRoy]

Okay well the past 2 days ive noticed a similar problem with my car regarding a low oil pressure.

The car in question is an AE92 and my observations have come from the standard dash gauge.

In the past the gauge has read just below the half way mark at idle and then at higher rpm it will rise to the around the 3/4 mark/just under the next marking on the guage, this next marking being the one above the half way point.

Yesterday i had been driving and noticed the guage at higher rpm was reading onto this 3/4 marking and edging above it which i have never seen it that high so this was my first concern. Once home i had stopped the car and gone inside for around 30 minutes before jumping back in the car and starting it up again.

Now once i started the car the oil pressure rose to just under 1/4 then stopped and sat there, but after a quick tap on the throttle to bring the revs up to about 1500 the pressure continued to rise and ended up where it normally sits.

Earlier tonight i did the same thing, hopped in the car after driving it and upon starting it up the oil pressure did the same thing, rose to just under 1/4 then stopped. I let it sit here for about 1 minute and after giving it another quick tap on the throttle it rose and went to its usual position.

I use 10w/40 castrol magnatec oil and have for the past 6yrs/100,000k's, and the oil was recently changed - about 1 month/1500km's ago.

I plan on getting one of these propper guages to check it out on the weekend along with checking out the gauge earth and sender wiring.

I understand that these electronic guages are not the most accurate of things but does anyone have any ideas what this could be or has anyone had a similar problem.