oil pressure woes

[rustfarmer]

Fresh rebuild, stock crank polished and checked, new oil pump, spun engine with fuel inop and ignition inop until oil pressure began to rise. Shimmed both oil pump bypass valve and oil pressure regulator valve 5mm. Upon cold start, aftermarket (cheap) mechanical oil gauge reads 60 psi at fast idle. When warm, runs at 20 to 30 cruising slowly and jumps to 40 as you rev it up some, but drops to dead zero, on the needle stop at hot idle. Rev it just a bit and it recovers to 10 quickly. So, the questions are 1, do I need to bleed the air out of the gauge capillary tube; 2 is a cheap 100 psi gauge to inaccurate to read the normally low idle pressure; 3 am I nuts to run the cooler line oil through the radiator trans cooler (which I though was a great idea as engine oil is normally much hotter than 180 degrees, true?) I know I probably should buy a big oil cooler, but this project has bled the wallet pretty dry. Thanks for all help, RF

 

[IJ.]

What were your bearing clearences?

What Oil?

I wouldn't bother running the cooler line through the Trans cooler, if it's the stock bypass cooler circuit just grab a big trans cooler so it'll actually do something..

 

[hvyman]

Or for moneys sake use a stock oil cooler.

What is the idle at? and what does the stock oil gauge do?

 

[nothingbetter]

keep in mind that the stock oil pressure is 4.3 psi when hot at an idle around 6-700. That is not a typo...4.3psi

 

[planemos]

I was watching my 22RE oil pressure gauge the other day and it does basically the same thing.

 

[rustfarmer]

I checked the TRSM again and notice that it shows a large oil cooler for cars with the auto trans, and a second small unit in series for the stick shift cars. My 87 non turbo came with the slush box and did not have any oil cooler at all. As I am now running a turbo 5 speed, all that came with the new engine was the small cooler, so I guess I need the larger one as well. My rule of thumb has always been 10 psi per 1000 rpm as a minimum correct oil pressure so I am uncomfortable with 4.3 at hot idle. Hell, my old VW bus would hold 7 psi after coming off an interstate run and I always felt that was marginal. I know this system is supposed to be high volume/low pressure but can someone explain what the engineer that dreamed this up had in mind? Any way, I plan to ad a large oil cooler and I have shortened the copper tube run to my old school mechanical gauge and plan to purge all air from that line as well. Fresh 10-30 castrol and Wix filter and we'll see what I've got. More to come, RF

 

[hvyman]

Its not pressure that the bearings need its flow. Get too much pressure and you wont have enough flow. Same goes for small block chevys.

You can shim the oil pump pop off valve 5mm with washers and the oil cooler pop off valve 5mm and raise the pressure up a little and get more flow. Most people do that.

Iirc all the stock oil coolers were the same size. Could be mistaken tho havent really looked at auto cars much.

It would also be better to use a 5w or 0w 30 over the 10w30. Gets to the bearings quicker when cold.

And switching from the stock oil cooling system to a full flow t stat controlled system with remote oil filter would be a much better system over the stock system.

 

[rustfarmer]

Thanks for the info. Please note that I had a sweet running gte and changed to full synthetic 0-40 and spun a rod bearing in 100 miles. Yes it was a used engine and ran well with 10-30 castrol, but spun #1 bearing so badly that in 10 miles there was no bearing shell left. I replaced the crank with a used unit that spec'ed perfect so was only polished and new Clevite bearing, oil pump, bored and new pistons, head worked, all new timing components, metal head gasket and ARP bolts, ect. Shimmed oil bypass and regulator and still seems very low pressure to me. I don't have an oil flow meter, nor have I have ever seen one, thus pressure is all I have to go by. After all the bucks and careful assembly with assembly lube and spinning up to show pressure prior to firing up, still good gauge reads zero at hot idle. When you say all stock coolers were the same size, have you looked at the TRSM? I have a cooler that is about 7 inches by 5 inches, which the TRSM shows as an additional cooler for stick shift cars.

 

[hvyman]

Thats the stock oil cooler. Mine for my 5 speed was about that size.

Idk what to tetll you about the oil. Ive been running gc 0w30 syn for about 5 years now.

 

[rustfarmer]

Just reworked engine cooler lines so not going thru radiator trans cooler but just thru the tiny stock cooler I have. Changed oil gauge to old known good unit and purge air from copper feed line. Same result. Good pressure while driving (I guess--15 to 20 at about 40 mph in 4th gear) but gauge rests on zero peg at idle. If I open the line to the gauge at idle I do get some oil flow, but I have to rev the engine some to get any reading on gauge. Fresh 10-30 Castrol oil. I am using 0-100 psi gauges as thats all that parts stores seem to sell these days. Are these gauges too inaccurate to read the normal low idle pressure? Hate to burn up a new engine and I'm afraid to run it with such low pressure. Any more ideas?

 

[jonahs_supra]

i recently installed a autometer oil psi gauge with electric sending unit
oil im using is 10w40 castrol gtx with 2k miles
motor has 156xxx miles(i dont know if its the original or not)

stock gauge:
cold idle=40psi
hot idle=20psi
2,500rpms at 65mph hot engine=40psi

autometer:
cold idle=40psi
hot idle=4ish psi lol...almost on zero
2,500rpms at 65mph hot engine=25psi
for every 1k rpms my oil pressure goes up 10psi

i havent any odd engine noises
so far so good

 

[hvyman]

Hot idle spec is 4.3 psi.

 

[rustfarmer]

Spoke with someone (Dan?) at Driftmotion late yesterday to ask about what oil pressure gauge they recommend for best reading of low hot idle pressure and he said experience has shown that the stock gauge usually matches the results of expensive aftermarket gauges, although the stock unit is somewhat slow in response time. He also said that one of the biggest worries with modified 7M's with lightened flywheels is the drivers tendency to rev the engine quickly from hot idle as oil pressure cannot build quickly enough to protect bearings, ect. I will re=install the stock sending unit today (PITA) to see what it shows. Probably should get a new sender, but don't want to try a cheap parts store unit so I'll try what I have first. Thanks to all for ideas and help. Hope the stocker shows some pressure at hot idle. RF

 

[suprarx7nut]

My stock gauge has shown nearly 0 psi on both engines I've had in the car. Both engines were/are in great shape. I'd definitely consult a known good, mechanical test gauge before worrying too much.

Stock gauge is not suitable for diagnosing any true engine problems, imo


Edit, just read about your comment, "not comfortable with 4.3 psi". Lol. The engine is designed for low pressure and is proven to work reliably. You must have had a problem with your previous motor. More pressure is not always a good thing. Pressure indicates resistance to flow, nothing more.

Sent from my ADR6400L using Tapatalk

 

[rustfarmer]

So just finished re-installing my stock oil gauge sender and testing the car. Gauge shows 20 psi cruising at 60 mph in 5th, and a hair less than 5 at hot idle, although if I let it sit at idle for several minuets the gauge slowly drops to almost zero. Wish I could afford the $250 for a real test instrument, but as pressure seems steady and will climb to 30+ when I build some revs I suppose I'll run it and hope for the best. Might change the 10-40 in 500 miles as break in is mostly done. Still makes me nervous to see the gauge so low. When purchased new from the dealer didn't folks complain about this? Now if I could just get the timing to set correctly i'd be a happy camper.

 

[suprarx7nut]

Might change the 10-40 in 500 miles as break in is mostly done. Still makes me nervous to see the gauge so low. When purchased new from the dealer didn't folks complain about this? Now if I could just get the timing to set correctly i'd be a happy camper.

They didn't complain because the system works as it should, lol. I think you are insisting that more oil pressure is needed and you're inferring the Toyota engineers that specd the system didn't know what they were doing.

MORE PRESSURE IS NOT NECESSARILY GOOD. pressure is a measure of resistance to flow in this case. Unless you run bigger clearances than stock spec a heavier oil is not what the doctor ordered.

just my .02
Sent from my ADR6400L using Tapatalk

 

[hvyman]

Why would anyone complain about the low oil pressure number? There motor wasnt knocking and ran great. You dont get rod knock for no reason on these motors, its from getting a bhg and letting water ruin bearings.

 

[rustfarmer]

Interesting that I had rod knock and spun bearing with no BHG, but it was a used JDM "less than 50 k" engine so I'll let that one go. However,can't quite stop thinking about the high volume/low pressure idea. Saying that pressure is just resistance to flow seems to me to be an over simplification. Bernoulli's principle continuity equation states that for fluid flowing through a pipe, as the radius decreases, the velocity increases. Furthermore, as velocity increases, pressure decreases which would seem a bit counter-intuitive a first. My point is that the speed of oil travel through the system should have an affect on heat transfer, and if lower pressure equals increased velocity perhaps those Toyo engineers were on to something. The weird part is that Nascar engines do not use this low pressure system, nor do formula 1 cars, nor do any other race engines I have heard of. And Driftmotion rebuilds factory 7M oil pumps to tighten up clearances and claim to yield 18 psi hot idle using a full flow filter and t-stat controlled cooler. I'm confused.

 

[jetjock]

While I'm not the Einstein you appear to be (although I am intimately familiar with Bernoulli) it seems to me if oil pressure was an actual problem your engine would have failed by now...

 

[hvyman]

Nascar is chevy and ford motors that run 20-30 psi at idle.
F1 is F1 and shouldnt be compared.

7m should have a 5mm washer to increase the pressure and get more flow. But that is it.
Trying to increase pressure with a thick oil is a no no.