QuestionQUESTION: Hi,
I've had periodic times when the oil pressure light comes on after my car heats up. A year ago, my mechanic had me switch to synthetic oil and the problem went away. Now it's back. I brought it to a Chrysler dealer (big mistake, I think) and they first said the problem was "deep in the block". Then they said it was caused by numerous oil leaks (but I don't lose more than a quart of oil every 3 months). Then when I said "Just give me back the car" they decided they knew what the problem was, replaced the oil sending switch and sent me on my way ($327 dollars later). I have heard this is a long-known problem with this engine and that it's really not repairable.
I'll decide what to do with the dealership later, but my question for you is, what is the likely problem? How long before the car fails? What will happen when it fails?
My mechanic prefers to work on foreign cars, so he has limits on what he will do with this one. I have another car, so I'm not really overly obsessed with getting this one perfect...I just need it to keep running.
Thanks for any advice.
ANSWER: Hi Paula,
It is a very high price for advice and changing the oil pressure sending unit. How much labor/time was charged? On most engines that sending unit is mounted right next to oil filter and shouldn't take more than 10 minutes to exchange that!
I would not be able to tell you even if you have a problem. If replacing the switch caused the light to no longer come "on" when at idle with a warm engine then that would show the problem was just the sender and had nothing to do with oil pressure being too low in actuality. This sort of a false warning is very common. I would therefore disregard that dire prognosis. If you really had to know you could have your mechanic measure the oil pressure with a calibrated gauge when warm at idle and at 3,000 rpm for which there is a minimum pressure spec (let me know which engine you have). (Perhaps the dealer did that, in which case the work order should tell you the results; so see if that was listed as part of the job/labor charge. The results should have been stated on the bill.)
But if it were my car with this history I would have done exactly the same thing...change to a different oil; and again should it pop up I would increase the "weight" of the oil by one step to improve the pressure readings and turn out the light.
You will just "keep running" is my prediction. If not, then it would likely just become harder to start, burn oil to a greater degree, and have reduced gas mileage.
But I would encourage you to question the bill from the dealer if the labor time is ridiculous.
Roland
---------- FOLLOW-UP ----------
QUESTION: Hi Roland,
I wasn't clear with you - the red light is STILL coming on. Changing the switch did nothing (which is why I'm very angry). According to what they wrote on the bill, the pressure is 48 psi cold, 15 psi hot. They did not specify whether that was at idle or 3000 rpm. My suspicion is it's at idle, but I really don't have the data. The engine is the 2.5 liter version. Is 15 psi out of the range of normal? I seem to remember reading somewhere that as low as 6 at idle is okay but I actually have no clue.
Regarding the charges, going in, I agreed first to a 1 hour minimum cost so I could actually find out what the problem was, and then when they said they weren't sure, I agreed to a second hour. I was pretty sure they were ripping me off, but I'd heard rumors that these engines have a tendency to freeze up, and was willing to pay that much to find the cause. I was clear with the service rep that I did not want to put a lot of money into the car. It was after he said they needed yet another hour (at $111 each) to go "deep in the block" that I insisted they return the car. All of a sudden they decided it was the switch, and charged me for yet another 1/2 hour to install it.
As for the bill, I called the service department today to dispute it, because they did not fix the problem. The service guy said "You agreed to it" and then told me they'd take me to court if I pursued the dispute. I think I'll take them up on that. I'll also post their name somewhere sometime on the net, and probably write a letter to my local paper.
But that's a separate issue. How does that pressure sound to you? I live in Miami. Does that put a limit on the heaviness of the oil I can put into it.
Thanks again! You're prompt and so far have been really helpful.
Best,
Paula
AnswerHi Paula,
Thanks for the further details. The factory stated minimum spec is 6 psi at idle and a minimum of 35 psi at 3,000 rpm, both measured hot. Because they didn't list the rpm I would call up and ask them to verify with the person who did the measurement what rpm these results are for? They are otherwise of no practical use to you. They should have measured both hot, not cold and hot and without a spec as to what rpm.
If it turns out that they are indeed for 3,000 rpm and you can believe them, then I would be inclined to increase the oil weight: if it is currently 10W-30 I would change to 20W-40 (if now 30W change to 40W). That will likely solve the light and the low pressure issue at the same time. If not, then I would investigate having the oil pump replaced WHEN you have gone 100,000 miles since the last time the timing belt was changed (which is the exact time to do the pump because it is easily accessible at that time).
The oil pressure warning light is presumably now accurate, so if it comes on while you are driving (not just idling) then you do have to take that seriously. But don't worry about it lighting at idle so long as it goes off as soon as you accelerate away.
Miami is a great place to need heavier oil. It is only in very cold climates where you would not want to have 40W for reasons of possible under-lubrication or inability to crank the engine fast enough to start it! You could even go to 20W-50 if necessary to get the light to behave where you live.
I would go back to regular oil as it tends to not run as "thin" as the synthetic and therefor would also show higher pressure at a given rpm and temperature.
