Is this a relief valve problem - oil pressure - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 09-20-2013, 09:57 AM   #1
Newb
Thread Starter
 
Join Date: Sep 2013
Posts: 10
Total Cats: -11
Default Is this a relief valve problem - oil pressure

When the car first starts up oil pressure is good, it is always good when car is cold pegging 60 without much rpm as expected on thick oil. When its hot though I sometimes see it drop very low at idle below 1000rpm, Less than 10psi. Other times it holds 15psi with no issue. Is this the symptom of a bad relief valve?
spforces is offline   Reply With Quote
Old 09-20-2013, 11:22 AM   #2
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,011
Total Cats: 583
Default

Might be the relief valve or your oil pump may be worn out. In either case, you're pulling the engine to repair.

But, before you do that, it is worth connecting another gauge. The OEM gauge sometimes reads incorrectly.

On cold start, you should see it go much higher than 60. 60 is a good pressure for normal cruising after reaching temperature.
hornetball is offline   Reply With Quote
Old 09-20-2013, 12:25 PM   #3
Junior Member
iTrader: (5)
 
Join Date: Mar 2012
Location: Gilbert, Az
Posts: 337
Total Cats: 26
Default

It also makes a difference how hot the oil is. When it's 115 out and I've had the A/C running and get off the freeway (having done 70 for ~30 mins), until the oil cools a bit driving on surface streets mine will hover in the ~10psi range at idle until it gets a chance to cool some. Under "normal" operating conditions mine sits in the 15-18 psi range at idle (850 rpm).

I've thought of getting an oil cooler to help fix this condition, but meh...
SJP0tato is offline   Reply With Quote
Old 09-20-2013, 01:10 PM   #4
Destroyer of Inconel
iTrader: (37)
 
EO2K's Avatar
 
Join Date: Apr 2010
Location: In ur driveway, abusin' ur WPA
Posts: 9,642
Total Cats: 954
Default

Quote:
Originally Posted by SJP0tato View Post
When it's 115 out and I've had the A/C running and get off the freeway (having done 70 for ~30 mins), until the oil cools a bit driving on surface streets mine will hover in the ~10psi range at idle until it gets a chance to cool some.
Does this cause scary rattling noises? Because I get noises after what you described, and I've always assumed it was heat and oil related. I'm reinstalling a legit OPG this weekend.
Quote:
Originally Posted by SJP0tato View Post
I've thought of getting an oil cooler to help fix this condition, but meh...
Hah! I was thinking the same, but I know its not going to fix a dubious oil pump.
EO2K is offline   Reply With Quote
Old 09-20-2013, 01:45 PM   #5
Newb
Thread Starter
 
Join Date: Sep 2013
Posts: 10
Total Cats: -11
Default

There are indeed scary rattling noises when I let it go low. I have seen it come very close yo reading zero and other times when I know the oil is hot it won't go below 15psi
spforces is offline   Reply With Quote
Old 09-20-2013, 01:54 PM   #6
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,011
Total Cats: 583
Default

BTW, what oil are you running? Diesel formulations are kind to our cars. Rotella T-6 seems to be the MT standard and is fairly inexpensive at Wally World. At temperature, T-6 acts like 40 weight and helps keep pressure up.
hornetball is offline   Reply With Quote
Old 09-20-2013, 02:22 PM   #7
Destroyer of Inconel
iTrader: (37)
 
EO2K's Avatar
 
Join Date: Apr 2010
Location: In ur driveway, abusin' ur WPA
Posts: 9,642
Total Cats: 954
Default

I don't know about OP, but I am running T6, that's what freaks me out
EO2K is offline   Reply With Quote
Old 09-20-2013, 02:28 PM   #8
Elite Member
iTrader: (2)
 
fooger03's Avatar
 
Join Date: Jan 2009
Location: Columbus, OH
Posts: 4,133
Total Cats: 188
Default

1995 and later cars have an oil pressure gauge that says "good" above 7 psi and "bad" below 7 psi. Apparently the people who designed your engine feel that 7 psi of oil pressure is safe.

When it's hot, I'm generally satisified with 10 psi per 1000 rpm. If you don't like the low pressure, then buy a thicker oil. Safety of your engine is not determined by oil pressure, it is determined by oil flow. When your oil is at 60 psi and flowing through the relief valve, your flow is reduced, and engine wear is accelerated. When the engine warms up, viscosity is reduced, pressure drops, flow increases, and your engine is happy. When you're idling at 800 rpm and no throttle, why do you feel you need 30 psi of oil pressure? No load on the engine, no speed on the spinny bits...just a thought.

People that complain about low oil pressure when hot idling (such as yourself) is the EXACT reason why Mazda replaced the oil pressure gauge with an idiot gauge in 1995. We have idiots to thank for the fact that we have to retrograde our oil pressure gauges and sensors. I feel like the most cost effective solution for you is to trade senders and gauges with a smart person who has a 95 or later gauge and sender.

Your car will still be happy, and you'll still be just as....uninformed.
fooger03 is offline   Reply With Quote
Old 09-20-2013, 02:50 PM   #9
Destroyer of Inconel
iTrader: (37)
 
EO2K's Avatar
 
Join Date: Apr 2010
Location: In ur driveway, abusin' ur WPA
Posts: 9,642
Total Cats: 954
Default

Quote:
Originally Posted by fooger03 View Post
People that complain about low oil pressure when hot idling (such as yourself) is the EXACT reason why Mazda replaced the oil pressure gauge with an idiot gauge in 1995.
Yes I'm familiar with how oil works with temperature But I think OP and I are in the same boat here: at what point does this go from being low pressure due to hot, thin oil to low pressure due to relief valve issue?

Quote:
Originally Posted by fooger03 View Post
Your car will still be happy, and you'll still be just as....uninformed.
Rattling from the engine is generally does not indicate a happy engine. I'm tempted to believe its actually a bad thing. Does your **** rattle at idle after a long highway run or a 20 minute session on a roadcoarse?

spforces: Sorry to threadjack, hopfuly this is relevant. What brand/weight of oil are you running?
EO2K is offline   Reply With Quote
Old 09-20-2013, 03:12 PM   #10
Elite Member
iTrader: (2)
 
fooger03's Avatar
 
Join Date: Jan 2009
Location: Columbus, OH
Posts: 4,133
Total Cats: 188
Default

Nope, no engine rattles. Running solid lifters. Typically see 8-10 psi at hot idle. Ocassionally down to 6psi if the fans kick on and the idle drops to 400 rpm for a quarter of a second. I would expect it to be a relief valve issue if the pressure falls relative to RPMs as RPMs increase. If my RPMs increased from 800 to 5000 and my oil pressure went from 8psi to 20psi...well, that would make me sad.
fooger03 is offline   Reply With Quote
Old 09-20-2013, 03:59 PM   #11
Destroyer of Inconel
iTrader: (37)
 
EO2K's Avatar
 
Join Date: Apr 2010
Location: In ur driveway, abusin' ur WPA
Posts: 9,642
Total Cats: 954
Default

Exactly

Quote:
Originally Posted by spforces View Post
There are indeed scary rattling noises when I let it go low. I have seen it come very close yo reading zero and other times when I know the oil is hot it won't go below 15psi
Sounds like OP and I have rattles with the same conditions, but I need to get some real OPG up in herr to confirm teh dataz.

FML. Maybe I should call Andrew and find out about a shortblock. I've been whomping on this thing for a while, I know its not going to last forever.
EO2K is offline   Reply With Quote
Old 09-20-2013, 08:50 PM   #12
Newb
Thread Starter
 
Join Date: Sep 2013
Posts: 10
Total Cats: -11
Default

Quote:
Originally Posted by fooger03 View Post
1995 and later cars have an oil pressure gauge that says "good" above 7 psi and "bad" below 7 psi. Apparently the people who designed your engine feel that 7 psi of oil pressure is safe.

When it's hot, I'm generally satisified with 10 psi per 1000 rpm. If you don't like the low pressure, then buy a thicker oil. Safety of your engine is not determined by oil pressure, it is determined by oil flow. When your oil is at 60 psi and flowing through the relief valve, your flow is reduced, and engine wear is accelerated. When the engine warms up, viscosity is reduced, pressure drops, flow increases, and your engine is happy. When you're idling at 800 rpm and no throttle, why do you feel you need 30 psi of oil pressure? No load on the engine, no speed on the spinny bits...just a thought.

People that complain about low oil pressure when hot idling (such as yourself) is the EXACT reason why Mazda replaced the oil pressure gauge with an idiot gauge in 1995. We have idiots to thank for the fact that we have to retrograde our oil pressure gauges and sensors. I feel like the most cost effective solution for you is to trade senders and gauges with a smart person who has a 95 or later gauge and sender.

Your car will still be happy, and you'll still be just as....uninformed.
Wow... I think I know how to use an oil gauge for intelligent people...such as yourself... When the gauge says its at its minimum and the lifters can't stay pumped up due to lack of pressure and are clanking against the cam I feel pretty sure I have an issue. My automotive service background and mechanical engineering degree don't mean I gave all the answers about my car but they are enough to go yo against someone who is just out to troll. Is my LOW oil pressure issue problem consistent with what those of you that have had relief valve problems have seen? That's all
spforces is offline   Reply With Quote
Old 09-20-2013, 08:55 PM   #13
Newb
Thread Starter
 
Join Date: Sep 2013
Posts: 10
Total Cats: -11
Default

Quote:
Originally Posted by EO2K View Post
Yes I'm familiar with how oil works with temperature But I think OP and I are in the same boat here: at what point does this go from being low pressure due to hot, thin oil to low pressure due to relief valve issue

Rattling from the engine is ally does not indicate a happy engine. I'm tempted to believe its actually a bad thing. Does your **** rattle at idle after a long highway run or a 20 minute session on a roadcoarse?

spforces: Sorry to threadjack, hopfuly this is relevant. What brand/weight of oil are you running?
I put in 10-40 in an effort to combat the issue so I don't think thin oil is my problem. No problem at all hope we can both learn something here from someone genuinely interested in helping us out!
spforces is offline   Reply With Quote
Old 09-30-2013, 06:31 PM   #14
Destroyer of Inconel
iTrader: (37)
 
EO2K's Avatar
 
Join Date: Apr 2010
Location: In ur driveway, abusin' ur WPA
Posts: 9,642
Total Cats: 954
Default

spforces: Do you have another gauge installed yet?

I can't find my stupid BSP adapter so I haven't installed mine yet
EO2K is offline   Reply With Quote
Old 09-30-2013, 09:16 PM   #15
Senior Member
iTrader: (3)
 
Join Date: Jul 2011
Location: STL
Posts: 528
Total Cats: 24
Default

Quote:
Originally Posted by fooger03 View Post
Nope, no engine rattles. Running solid lifters. Typically see 8-10 psi at hot idle. Ocassionally down to 6psi if the fans kick on and the idle drops to 400 rpm for a quarter of a second.
I see the same thing, 8-10psi hot idle. I've never paid attention during near-stall speeds but I wouldn't be surprised if it drops like yours does. Running Rotella T6 and VEI gauge in with the sender in stock location. I may switch back to Mobil 1 0w-40, it was consistently 1-2psi higher than with T6.

Oddly enough, with the stock sender completely removed the stock gauge still reads as if there was sufficient oil pressure.

All this time I assumed the low pressure was caused by FMs -8an cooler lines, gauge and cooler were installed at the same time.
midpack is offline   Reply With Quote
Old 10-01-2013, 02:38 PM   #16
Elite Member
iTrader: (2)
 
Join Date: Dec 2011
Posts: 1,517
Total Cats: 142
Default

Quote:
Originally Posted by spforces View Post
When the car first starts up oil pressure is good, it is always good when car is cold pegging 60 without much rpm as expected on thick oil. When its hot though I sometimes see it drop very low at idle below 1000rpm, Less than 10psi. Other times it holds 15psi with no issue. Is this the symptom of a bad relief valve?
Given that variability, is there any chance it could just be some glitching in the pressure sending unit?
good2go is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 59 12-15-2017 09:00 PM
OTS Bilstein to motorsports ASN conversion stoves Suspension, Brakes, Drivetrain 5 04-21-2016 04:00 PM
Moroso Air Oil Separator Catch Can Aroundcorner Miata parts for sale/trade 2 10-01-2015 04:20 PM
Leaky Wilwoods mx592 Suspension, Brakes, Drivetrain 1 10-01-2015 01:45 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 12:56 PM.