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Old 04-23-2007, 11:47 AM   #1
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Default Theoretical low oil pressure question.

Hey all -

I'll start from the beginning, as there may be a few details that are important to the question - please bear with me.

Four weeks ago I spun a bearing and seized my motor. The engine had around 125K on it (I bought the car around 115K or so). The oil pressure gage would read around 45-50 cold, and once warm would drop to 10-15 at idle. In the summer, it would drop to 0 at idle, and I'd get the warning bell.

So I ordered a used motor with 51K on it, and 2 weeks ago the swap was complete. So I get the call from the mechanic - "I have some good news, and some bad news". The good news is that it starts right up. The bad news? Oh, there'* no oil pressure. Yes, I said, that is very bad news. The actual symptoms were that at high RPM it would show about 35-40, and at idle zero, both of these readings were at warm or cold.

He said he thought it might be the oil pressure sender, and was going to put the one from my old motor on to see if that helped. He did that, it didn't help. I asked if he had a mechanical gage he could put on to get an actual reading. He said he did, but first he wanted to go buy a new sender. So he did that, and it didn't help. I asked if he had put on the mechanical gage - he said he did and that "it had oil pressure".

Then he told me another problem: The oil pan was dented, and he thought it could be the cause. Unfortunately, it was the weekend, and I couldn't get ahold of the salvage yard to see if swapping the oil pan would void my warranty. In the end we decided to wait till I could talk to the salvage yard on Monday, as the mech. gage showed pressure.

So I got the car back, and took a look at the oil pan. Dented was an understatement, crushed is more like it. I checked the dipstick: it read 1 quart high with 5 quarts in, so I had a 1 quart displacement. Very clearly "dented" enough to interfere with the oil pickup as well.

I've read all the posts about what too much oil does to your motor, and so I decided not to drive the car until the oil pan was swapped. The salvage yard also said that swapping the oil pan would not void the warranty, and actually went so far as to say they were shocked he didn't change it anyway, even if it wasn't damaged, almost as if this is something that is done as a matter of course. I also pulled the dash cluster, disassembled and cleaned it. No change in behavior.

This past Thursday he swapped the oil pan and pickup tube. This helped a great deal - when cold I read about 60-65, at idle and at road speed. Once warm, I read 40-45 at road speed. But at idle.... zero. Basically going down the road I'm fine. At a stop light, I'm sweating bullets.

I asked the mechanic - "you did put on a mechanical gage, didn't you"? He said - "yes, but I didn't let it warm up". Which kind of shocked me, but I didn't ask "why not"?

So today I'm going to put on a mech. gage and see if the problem is the engine or the gage.

And now the question: Assuming the problem is the engine, what would be the most likely culprit for no oil pressure at idle? I can't see it being the oil pump, based on the mileage on the engine and all the other posts I've read in here about how the oil pump functions in these motors.

One other bit of info: When you start the engine, you can hear the lifters tick for about 30 seconds, and then the motor sounds great. This is the case every time, wether the engine is hot or cold.

I know the thing to do is get the mech gage hooked up to find out if I actually have an issue or not, but I'm just throwing this out there in the event the mech. gage shows the same thing as the electronic one.

Here'* another reason for the question: I have a 6 month warranty on the engine, but it doesn't cover labor or shipping. So if it is the oil pump, or something else defective that causes me to put yet another motor in, I'm looking at another $1100 (shipping + labor). I guess what it comes down to is that if it is the engine, my low cost option is just to fix the problem vs. pulling/shipping the motor.

Sorry for the long post, and thanks in advance for any comments.
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Old 04-23-2007, 11:48 AM   #2
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Locked for double-posting.

Please read your other topic, and post this there.
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