Oil Pressure drop

[bigboostedmk3]

Now i know this may not seem like a big deal but i know how dangerous low oil pressure and these 7m's are so here goes. I have an aftermarket oil pressure gauage(autometer) and its been working fine reads about 14-15 at warm idle and like 38-40 at 110 km/h at 3000 rpm. My problem is that just a coup[le of days ago i noticed it dropped about 5 psi so i changed the oil and its still down 5 psi at every rpm. Any ideas.

thanks
bobby

 

[suprahooked]

Toyota designed the 7m to be high volume low pressure system so you are ok to be 5 psi at idle.

 

[starscream5000]

He said every RPM...

 

[cjsupra90]

Toyota designed the 7m to be high volume low pressure system so you are ok to be 5 psi at idle.

He said that the 5 PSI drop was every where, not just at idle.

You can not have nor did Toyota design a High Volume / Low Pressure system. Oil Pumps are positive displacement devices and pressure is a byproduct of the volume displaced and the restriction in flow to that volume. The volume is consistant dependent on the rpm of the pump and the pressure will vary based on several reasons. All of those reasons have to do with restriction to the flow of that volume or loss of flow volume.

Having said that, the two possible causes are either a problem with the pump and its not displacing that correct volume therefore a loss of output volume from the pump (Examples, an excessively worn pump or crack in the pump body.) or there is a loss of flow restriction (examples, warn engine bearing(s), anytype of leak post pump like a loose fitting on the crossover pipe, a crack in the crossover pipe, a crack in a oil galley in the block, exc.......)

 

[suprahooked]

Sorry i missed that part. (5 psi at every rpm. ):nono:

 

[jetjock]

Meh, could simply be a viscosity change due to several reasons. Otherwise what CJ said was, well, very well said.

 

[p5150]

He said that the 5 PSI drop was every where, not just at idle.

You can not have nor did Toyota design a High Volume / Low Pressure system.

Why does the TSRM state that minimum oil pressure is 4.something PSI at idle?

Your drop in pressure might be due to the warmer weather. You should run thicker oil in the summer than you would in the cold.

 

[starscream5000]

Warmer weather isn't going to lower oil pressure to 5 psi at any RPM. There is either something seriously wrong with his motor, or the gauge is faulty. Check the lines going into the gauge for leaks (if it's a mechanical gauge).

 

[cjsupra90]

Why does the TSRM state that minimum oil pressure is 4.something PSI at idle?

Not fully sure as to why you are asking that or what exactly you are asking and how it pretains to this thread, but a basic answer is cause that is the minimum acceptable pressure for idle conditions. Anything less, then you have a problem somwhere.

One thing to remember here guys and not that I am saying not to worry about it, but oil pressure is not quite as important as a lot of people seem to think that it is. Yes it is important, but the molecular sheer strength of the oil is what is key to a good lubricating system. This is why synthetic oils are better then conventional oils and almost all are of lower viscousity ratings too for that matter which inturn will cause a loss of pressure depending on what viscousity conventional oil that was being used if a change over was maid..

 

[mkIIIman089]

Warmer weather isn't going to lower oil pressure to 5 psi at any RPM.

I'm pretty sure he lost 5 psi off of what he was seeing normally, not just 5 psi total, LOL.

My bet is just that you got it a little warmer then the temp you are used to checking pressure at.

 

[bigboostedmk3]

Thanks for all the input guys. The guage is new and its electrical, the engine and oil pump both have less than 20,000 just rebuilt the engine middle of last summer. No visible cracks or leaks anywhere and i am running new 10w30 castrol gtx oil. Normally like i said when cruising its at about 40 or so and now its at 35 or so. The weather has gotten signisficantly hotter and more humid, dont really know if it would affect it that much. ALso the engine still runs the same and still pulls hard. Very confusing.

Thanks
Bobby

 

[starscream5000]

Can you give us a comparison of what the oil pressures are at given RPM's at full operating temps now that they've decreased some?

mkIIIman089: yeah, just noticed that .

 

[bigboostedmk3]

at normal operating temperature at 3000 rpm, about 110km/h in 5th gear it used to be 40 psi and now its 35 or so.

 

[starscream5000]

That should be fine. Is the warm idle still about 14 psi or down about 5 psi?

 

[mkIIIman089]

The weather has gotten signisficantly hotter

As I suspected, thats the reason for your pressure drop. You would be amazed once you crest the 100C mark for oil temp how fast viscosity drops.

EDIT: You are below minimum for TSRM spec... so I would be careful. Normally I would never recommend this but maybe go to a little thicker oil to bump it up a bit. Sounds like your tolerances are maybe a little on the big side.

 

[bigboostedmk3]

At an idle its about 12, 2000 rpm about 25, 3000 rpm 35-36, 4000 rpm 40 or so have not payed attention after 4000 concentrating to hard on when to shift and watching traffic

 

[bigboostedmk3]

it just scares the hell out of me cuz i have already lost one engine cuz of a drop in oil pressure so now i am more paranoid about it

 

[starscream5000]

Unless you've done away with the stock oiling setup, you're not going to see a huge amount over 40psi as the oil starts to be bled off back into the oil pan at that amount.

 

[bigboostedmk3]

do you think its still safe to be pushing it hard i mean I am putting a new turbo on in the next two weeks which will double my power output compared to the one i am running on now

 

[starscream5000]

I see nothing wrong with the pressures you are running right now...