Question on oil pressure.

ComradeTony · Post by **ComradeTony** » Wed Mar 12, 2008 7:12 pm

So today I took my car to my mechanic for an inspection. He said that he believed there was an oil pressure problem because after a 3 mile test drive when he returned to idle, the pressure dropped from 60psi (cruising) to around 20 psi (idle). Now to me this sounds normal. As the oil heats up it becomes more viscous and therefore creates less pressure in the system. This would be especially true at idle when the engine isn't circulating a whole lot of oil to begin with. However he is the mechanic and I am not.

What do you guys think?

hockeystyx16 · Post by **hockeystyx16** » Wed Mar 12, 2008 7:17 pm

that mechanic is an idiot. your right, cold oil is think and creates a lot of resistance, and pressure is resistance to flow. as it warms up and thins out, it flows better, so the pressure comes down.

my car cold idles at 60 psi, warm idle at 15.

ComradeTony · Post by **ComradeTony** » Wed Mar 12, 2008 7:19 pm

He's a really honest guy that does work for my whole family, and I just find it hard to believe he'd make such a simple mistake. He did also tell me that my car had probably been in an accident before as the frame looks to have been repaired. He also said that I might have a slight head gasket leak and maybe that is why he thought I could have an oil pressure leak?

But from my understanding, any kind of serious oil pressure leak should be detectable while driving normally. The pressure stays at a fine level while driving at constant RPM so I don't see the problem.

Leedeth · Post by **Leedeth** » Wed Mar 12, 2008 7:25 pm

Did he actually take you to your car and point out all the problems? IMO you shouldn't trust a mechanic that doesn't do that.

ComradeTony · Post by **ComradeTony** » Wed Mar 12, 2008 7:26 pm

He told me this over the phone. Like I said before he does work for my family and is really really honest from what I know. He didn't even charge me a dime for the inspection.

Leedeth · Post by **Leedeth** » Wed Mar 12, 2008 7:31 pm

You really should see this stuff firsthand. Checking for a head gasket leak is easy, just check the oil and coolant. Dunno about the oil pressure, maybe get him to take you on a drive and show you the readings on the gauge?

ComradeTony · Post by **ComradeTony** » Wed Mar 12, 2008 7:34 pm

The readings were just while parked. And how do you check for a headgasket leak?

Leedeth · Post by **Leedeth** » Wed Mar 12, 2008 7:40 pm

Ok I'm a nub. I thought that a gasket leak would always result in the coolant and oil mixing, but that's not the case.

http://en.wikipedia.org/wiki/Head_gasket

Occasionally, the compression in the cylinder will cause a leak to form in the gasket and the gasket will have to be replaced, or severe damage can take place (a "blown" head gasket). This problem has been exacerbated by the use of aluminum rather than iron cylinder heads; while lighter than iron, aluminum has a much greater thermal expansion rate, which in turn causes a great deal more stress to be placed on the head gasket. Engine makers have responded to this by adding a non-stick coating such as Teflon to the surface of the head gasket.

If the gasket fails, a variety of problems can occur, from compression loss (leading to power reduction, or a rough engine), to exhaust gases being forced into the cooling system, leading to the engine overheating and increased engine wear due to the motor oil being mixed with antifreeze. Coolant can leak into the cylinders, causing the exhaust to issue steam[3] and the catalytic converter to be damaged. If a very large amount of coolant does this, hydrolock can occur, causing extensive engine damage. Sometimes, all that may happen when a head gasket is blown is excessive steam erupting from the tailpipe and the engine may act and drive like normal.

Head gasket condition can be investigated by checking the compression pressure with a pressure gauge, or better, a leak-down test, and/or noting any indication of combustion gasses in the cooling system on a water-cooled engine. Oil mixed with coolant and excessive coolant loss with no apparent cause, or presence of carbon monoxide or hydrocarbon gases in the expansion tank of the cooling system can also be signs of head gasket problems.

Driving with a blown head gasket (if possible) can cause additional extensive damage due to overheating or loss of lubrication.

Blue exhaust smoke may be indicative of oil-burning.

ComradeTony · Post by **ComradeTony** » Wed Mar 12, 2008 7:43 pm

He didn't say it was a severe headgasket leak, and he actually said just some sealant would fix it (yet he didn't do this). From reading that it seems like if I had a severe problem I would definitely notice this.

Anyways my whole reason for getting this inspection was to get ready for autoX. He told me not to race the car because of the oil and headgasket issues. What do you think I should do?

hockeystyx16 · Post by **hockeystyx16** » Wed Mar 12, 2008 8:21 pm

forget about autox with a leaking head gasket, fix it right. those head gasket sealers are very african repairs to be honest with you. either fix it right or dont mess with it.

from the information you gave us, you dont have an oil pressure problem. you got high reading when cold and low reading when warm, thats normal, thats what oil does, it thins out and pressure gets lower, anyone who knows dick about cars knows this. if your oir pressure is erratic at a certain rpm, then you got problems. if your oil pressure is jsut plain too low (60 psi cold and 20 psi warm at idle is not too low) then you got problems. but from what i know, you dont have oil problems.

but fix the head gasket, thats kinda a big deal

ComradeTony · Post by **ComradeTony** » Wed Mar 12, 2008 8:32 pm

Hm. Thanks for the feedback. I need to get the timing belt changed and that needs to be done at the dealership. I suppose I could have them check for headgasket problems but I'm sure they would lie to me.

hockeystyx16 · Post by **hockeystyx16** » Wed Mar 12, 2008 9:01 pm

wheres your timing belt on the engine, if its on the front, it would be easy. you got any tools?

i highly suggest learning to work on your car yourself, it saves so much money and bullsh1t. for the most repairs, all you need is a jack, jackstands, and a simple set of tools. rachets, sockets, breaker bar, BFH, 4 way, some wrenches, a vise grip or 2, and some misc pliers. all can be had for cheap at harbor freight.

and then you be like me, get air tools and all the sudden turning a rachet is a lot of work lol

ComradeTony · Post by **ComradeTony** » Wed Mar 12, 2008 9:28 pm

It is on the front. But apparently it requires a special tool to remove. Also wouldn't you have to line it up just right or the cams would get mis-timed?

I really want to learn how to work on my own car, but no one in my family knows how to do. I also have no garage, only a driveway.

Bawked · Post by **Bawked** » Wed Mar 12, 2008 10:22 pm

hockeystyx16 wrote:wheres your timing belt on the engine, if its on the front, it would be easy. you got any tools?

i highly suggest learning to work on your car yourself, it saves so much money and bullsh1t. for the most repairs, all you need is a jack, jackstands, and a simple set of tools. rachets, sockets, breaker bar, BFH, 4 way, some wrenches, a vise grip or 2, and some misc pliers. all can be had for cheap at harbor freight.

and then you be like me, get air tools and all the sudden turning a rachet is a lot of work lol

I'm pretty sure i'll be getting a mr2 but one thing I may get a mechanic to do is the timing belt... It just looks like a PITA... meh i'll prolly jst go to my brothers and get him to help me do it up when i get one

hockeystyx16 · Post by **hockeystyx16** » Wed Mar 12, 2008 10:51 pm

ComradeTony wrote:It is on the front. But apparently it requires a special tool to remove. Also wouldn't you have to line it up just right or the cams would get mis-timed?

its on the front of a boxer, should be real easy to get to. i havent really heard of a lot of cars needing special complicated tools to do a timing belt job, mine just took some basic hand tools. and they put marks on the cam pulleys and the crank pulley to get you to line them up right.