Recently, the oil warning light has been coming on intermittently on my 98 Toyota RAV4. The first time this happened I immediately turned the vehicle off and checked the oil, which appears to be slightly overfilled (synthetic 5w-30, in case anyone cares). When I turned it back on, the light was gone. I notice this mostly on startup (it’s always damned cold here) and thought maybe thick oil + slight overfill = high pressure warning. Lately, however, it’s started coming on randomly while driving after warmup. If I immediately shut the car off, then start it up again, this turns the light off I’d say 50% of the time. Also, sometimes dropping a gear and increasing the RPMs turns it off. So, auto dopers, what do you think this is? Bad sender unit, overfilled or get it looked at immediately??
If it’s only slightly overfilled, that’s not a problem. On most cars, up to a quart over isn’t really a concern.
I’ve never seen any car with any kind of warning for oil pressure too high. The warnings are for pressure too low.
The first thing to do is a visual inspection of the wire to the sending unit, to see if it’s chafed anywhere and possibly shorting to some part of the engine. Otherwise, it may be a faulty oil sending unit, or the oil pressure may indeed be getting too low sometimes. There are two ways to approach it: test the oil pressure with a mechanical gauge, or replace the sending unit and see what happens.
If the sender is replaced and it eliminates the sympom, great - it’s okay, and you’re done. If the symptom persists, then it’s time to test the pressure.
Testing first offers the advantage of knowing for sure what the oil pressure is, which means peace of mind if it’s good (just need to replace the sender), or if it’s bad, not buying a sender that’s not needed. Replacing the sender first is a gamble, but one that often pays off. But as to which to recommend doing first, it’s strictly a guess - may as well flip a coin.
ETA: If it’s a bad sender, it’s not urgent. If the oil pressure is failing, it’s potentially serious and of some urgency. Since we can’t know which it might be, the wisest course is to act quickly.
I had this exact same problem with my 98 Camry this time a year ago (so also in cold weather). What it was was the oil intake valve was hopelessly clogged up. I think it was about an $800 repair job.
The problems you’re having are very similar to mine…the oil pressure light would come on and would go out when I would rev the engine. And at first it only happened sporadically but after a few days this was a constant problem. I would say just take it in. I tried changing my oil and oil filter but that didn’t actually help me at all.
Dodge trucks were notorious for this as well. The problem was an intake from the oil pan that was designed too narrow. Any (and I mean any) amount of sludge in the pan would clog that intake. The results were far more than the $800 repair mentioned above - it was a $6000 engine replacement because it clogged. (You would want to prevent this, I am sure.) My advice is to get thee to a mechanic!
Ok, I’m going to take it in. It will have to wait until the new year as everything’s closed until then. I’ll try not to drive it too much. I drove all over the place this morning and the light didn’t come on once.