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Old 29 Nov 2017, 10:57 am
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Default Too much oil pressure?

I have a strange issue that just popped up on my 2005 PT Cruiser GT. I've had the oil pressure sending unit replaced four times in the past six months because it starts leaking. I've read several places that these fail, especially when you use NAPA parts (my mechanic won't use anyone else, unfortunately). After replacing it last week it started leaking the day after and my oil light came on. It's only on at idle, if I get above 1k RPM it goes away, but comes back when the clutch is depressed.

I took it back to my mechanic (who's getting frustrated with me and my car at this point) and he put a mechanical gauge on it. At idle it has about 90PSI of oil pressure, at 3,000 RPM it buried his gauge at 120PSI. The only thing he can think of that's failing is the oil pressure relief valve in the oil pump. This costs an arm and a leg to replace because you have to remove so many things.

Have you guys ever heard of this failing? I am under the understanding that these relief valves are a spring and a ball, if they fail they just stop working and you get low oil pressure, not high?

Any input would be appreciated. I have the money to fix it, but if I fix it I'm going to just keep the car (Which isn't a bad thing, unless you're my wife) but I'd rather not spend $1,000 if I don't need to.

I change my oil every 3-5 months (depends on mileage) with Valvoline Full Synthetic 5w30. The oil is always clean when I change it. Every maintenance piece has been done before it was scheduled, including water pump, timing belt, etc. I've replaced most sensors under the hood trying to chase a problem when I first bought it.
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Old 29 Nov 2017, 12:02 pm
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Default Re: Too much oil pressure?

if the light comes on under 1k rpm, that would indicate less than ~4psi. (or a failing pressure switch)

did you SEE the gauge he installed? something sounds weird here. i dont think a PT at idle, even with no pressure relief valve, would be anywhere near 90psi
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Old 29 Nov 2017, 12:27 pm
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Default Re: Too much oil pressure?

These sending units if they are not carefully installed can become damaged and will fail prematurely. The brand has little to do with why yours are failing.

The GT oil pump design can build very high oil pressure. The flow pattern is terrible from the factory design. This was why Chrysler started to place a plastic restrictor in the block.

"90psi is not out of the ordinary at idle" Ed Peters, Modern Performance
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Last edited by NitroPT; 29 Nov 2017 at 12:29 pm.
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Old 29 Nov 2017, 12:34 pm
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Default Re: Too much oil pressure?

Quote:
Originally Posted by rob302 View Post
if the light comes on under 1k rpm, that would indicate less than ~4psi. (or a failing pressure switch)

did you SEE the gauge he installed? something sounds weird here. i dont think a PT at idle, even with no pressure relief valve, would be anywhere near 90psi
I agree with Rob.

Should not use any sealant on the threads when installing. Be careful not to over tighten and all the electrical connectors should be cleaned with an electrical parts cleaner.
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Last edited by ptcruisersteve; 29 Nov 2017 at 01:50 pm.
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Old 29 Nov 2017, 01:28 pm
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Default Re: Too much oil pressure?

Quote:
Originally Posted by rob302 View Post
if the light comes on under 1k rpm, that would indicate less than ~4psi. (or a failing pressure switch)

did you SEE the gauge he installed? something sounds weird here. i dont think a PT at idle, even with no pressure relief valve, would be anywhere near 90psi
Would the switch start failing if oil is leaking out from it? I have oil spots in my garage from it leaking.

I did not see the gauge when he installed it, but it's a mechanic I very much trust. I've been taking my stuff to him for 15 years now without any issues whatsoever. It's generally a wait of a month or so before he can get you in because he's so trusted around here.

Quote:
Originally Posted by NitroPT View Post
These sending units if they are not carefully installed can become damaged and will fail prematurely. The brand has little to do with why yours are failing.

The GT oil pump design can build very high oil pressure. The flow pattern is terrible from the factory design. This was why Chrysler started to place a plastic restrictor in the block.

"90psi is not out of the ordinary at idle" Ed Peters, Modern Performance
This is the fourth one that has been replaced, I mentioned they are prone to failure if not installed properly and he said that he was very careful when installing them, especially since we've had them fail before.

90 psi is more than double the spec amount, are you sure on that quote? I've talked to several people who build turbo cars strictly for racing and they've never heard of oil pressure being that high on a 2.4, especially a stock 2.4.

edit: Spec; curb idle 4 psi, 3000RPM 25-80psi
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Old 29 Nov 2017, 01:47 pm
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Default Re: Too much oil pressure?

a 4psi idle pressure won't be NEAR causing the bypass valve to do anything. so the bypass valve is 100% not the problem. i would just change the switch again. mine was $13 at autozone. it's very easy to change. the hardest part is unplugging the electrical connector.


there is a prized mechanic here and IDK if he had a mini stroke or what but he closed for a week for health issues, reopened and now doesn't really seem to care or do good work anymore. . went from amazing to odd overnight. perhaps your mechanic is starting to go bad or maybe his gauge is broken
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Old 29 Nov 2017, 03:09 pm
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Default Re: Too much oil pressure?

Quote:
Originally Posted by skitzo_inc View Post
90 psi is more than double the spec amount, are you sure on that quote? I've talked to several people who build turbo cars strictly for racing and they've never heard of oil pressure being that high on a 2.4, especially a stock 2.4.

edit: Spec; curb idle 4 psi, 3000RPM 25-80psi
I have a hand ported and modified version of the GT 2.4 oil pump done by Ed the same only with a little more personal attention to detail he does for Modern Performance. I looked at it before I posted and didn't see where anything could cause extreme oil pressure as described by you? My stock oil pump on my 05 GT at 1100 rpm idle speed cold 60-70+psi. If I even blip the throttle before the engine warms up it shots to 95-110psi. I did think at first that your report was unusual so as I was posting my response I was talking to "ED" (recovering from side effects of the flu shot) and the short version of our 40 minute conversation exactly what I quoted and even asked him twice about that.
BTW ED currently just got back from racing his very well built Track NEON and is at the moment building a performance engine for another customer of his. He is one of the most well known in the NEON Racing group for many years.
Cory @ Modern Performance is an great place to buy upgraded PT Cruiser parts and get great advise.
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Last edited by NitroPT; 29 Nov 2017 at 03:16 pm.
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Old 29 Nov 2017, 05:27 pm
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Default Re: Too much oil pressure?

Quote:
Originally Posted by NitroPT View Post
I have a hand ported and modified version of the GT 2.4 oil pump done by Ed the same only with a little more personal attention to detail he does for Modern Performance. I looked at it before I posted and didn't see where anything could cause extreme oil pressure as described by you? My stock oil pump on my 05 GT at 1100 rpm idle speed cold 60-70+psi. If I even blip the throttle before the engine warms up it shots to 95-110psi. I did think at first that your report was unusual so as I was posting my response I was talking to "ED" (recovering from side effects of the flu shot) and the short version of our 40 minute conversation exactly what I quoted and even asked him twice about that.
BTW ED currently just got back from racing his very well built Track NEON and is at the moment building a performance engine for another customer of his. He is one of the most well known in the NEON Racing group for many years.
Cory @ Modern Performance is an great place to buy upgraded PT Cruiser parts and get great advise.
I'm kind of confused. You said that you don't see anything that could cause the extreme oil pressure I stated but then said that if you blip the throttle at warm up it goes to what I described?

Is it extreme or normal? I don't know of any engine where 90 psi on idle is normal...
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Old 29 Nov 2017, 05:45 pm
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Default Re: Too much oil pressure?

Maybe you might just change your oil sender again as it was suggested?

If anyone else has actually tested their oil pressure with an external mechanical OP gauge or has a mechanical (not electric) aftermarket gauge in their PT Cruiser they might respond and let you know what they are getting in their PT Turbo model engines for oil pressure.
Other wise if you are that concerned the only resolve is only to replace the oil pump!

These pumps are not really a serviceable parts even off the engine. They are however relatively inexpensive for the part itself.

https://www.ebay.com/itm/New-Oil-Pum...lZsTVk&vxp=mtr
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Old 30 Nov 2017, 05:14 am
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Default Re: Too much oil pressure?

I don't know if it will help, but here's some thoughts. I just fixed a problem on an '04 Neon with the oil pressure switch (similar to the PT, oiling systems have a lot in common).

The Neon oil light stayed on from start-up a couple of times. Oil level OK, no unusual sounds from the engine. I discussed the problem with my brother, a long time mechanic. When I got under the car it was obvious the oil pressure switch was leaking oil. I replaced it, seems OK now.

I took the old switch apart at work, using a lathe to cut off the crimp where they assemble the switch. There's a diaphragm in the switch, that's what seals the switch. The oil pressure plays against one side of the diaphragm. On the other side of the diaphragm is a spring and electrical contacts. At rest the spring presses the contacts closed (oil light on). When oil pressure builds, the diaphragm is pushed back a little against the spring, opening the electrical contacts (oil light off).

When the diaphragm leaks, oil gets into the cavity where the electrical contacts are and the oil eventually leaks out of the switch. What I believe was happening was that when the oil filled the cavity where the electrical contacts are, it hydro-locked the switch. As the oil pressure built, the diaphragm couldn't move because it had oil (a not compressible fluid) on both sides. This kept the contacts closed and the oil light on. This is why a common symptom of a failed oil pressure switch is that the oil light stays on.

Talking with my brother (we have Sunday breakfast together), he explained oil pressure at idle is typically very very low, perhaps even just a couple of PSI. As the engine RPM builds, the oil pressure builds until the relief valve opens. As you said, the oil pressure relief valve is just a spring against a poppet that opens when the pressure gets high enough, regulating the maximum pressure (that's the 25 to 80 PSI). If the oil pressure relief valve sticks open, oil pressure would not build up. If the oil pressure relief valve sticks closed, the maximum oil pressure would not be limited.

The high oil pressure at 3,000 RPM (pegging the gauge) would indicate to me a stuck-closed oil pressure relief valve. The pressure will build until something gives, the weakest link, the diaphragm in the oil pressure switch.

The curious part is your high oil pressure at idle. I believe the spec should be around 4 PSI (I don't have the number for your specific Cruiser). That part of the problem, I don't understand.
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