MX-3.com

How are you guys? I'm new to the board and own 95 MX-3 4 cylinder w/automatic transmission. It has 122,000 miles on it as of today. It's been running pretty good with no major problems since I purchsed new back in 1995. I am currently having a problem with oil pressure light. It's on after I turn on the ignition and goes away a couple of minutes later. It used be off right away and never did this before and I've had this problem for 2 weeks now. It looks like if I start driving and make turns, the light goes away. I've checked oil level several times, and it's full. After the last oil change, I've driven about 1,500 miles. I've been using same engine oil all the time. Do I have a bad oil pressure sender unit? I wonder if anyone has same experience. I hope someone could help me out. BTW, I searched the forum, but nothing came up. Is search working?

the engine isn't making any noise, like valve tapping? if not it's probably the oil pressure switch. if the motor is tapping a bit it could be the oil pump. my guess is the switch though.

probably the oil pressure switch.

I concur.. if there is no unusual valve train noise.. its most likely just the oil pressure sending unit.

Tunes67

Thanks for the replies. No. There's no tapping noise. Engine sounds normal. Looks like I have to change the oil pressure sending unit. Where is it located by the way? Is it something that I can replace at home or should I take it to the shop? I don't have much experience on mechanic stuff though.

Go to the home page of this site. (http://www.mx-3.com) in the links on the left side of the page you will find the Online Shop Manual. You will find everything you need to change it out there. It should be very simple & straight forward. Unplug the single wire the goes to the sending unit. Unthread the sending unit from the block. Thread in the new sending unit and plug the wire back in. The shop manual should show you where the sending unit is located.

Tunes67

Got it! Thanks for the info. The shop manual looks great. Didn't even know the link was there. The unit was right next to the oil filter. I just called the dealership and it was $20 or so. Luckily, they have it in stock. I'll pick it up tonight and replace it.

Speaking of unusual valve train noise, I hear that sometimes. 100% of the time, early in the morning when it's cold outside. After the car warms up, tapping noise goes away. If it's warm, I never hear it. Sounds like it's coming from right under the valve cover. It's one thing that's been bugging me for a long time. IIRC, it's started happening since I replaced timing belt and water pump a couple of years ago. Any ideas?

Very typical.. that is your Hydraulic Lifters. When its cold outside, you engine oil is more viscous and doesnt flow quite as easily, so it takes a bit longer for your Hydraulic Lifters to pump up. So they make a tapping sound until they do pump up. Running a thinner weight oil in the winter 5-30W will help this a bit. This is a VERY common issue with these DOHC engines and mine does it too. But its nothing to really be concerned about. Mazda eventually went to a solid lifter design as a result of problems with these Hydraulic Lifters (Also referred to as HLA). As your HLA ages.. the lifters dont stay pumped up for as long as they did when they were new. So over night the oil slowly drains out of them.. so when you start up in the morning.. they have to pump up again. If you do feel like this is something you want taken care of.. you can replace your lifters.. just make sure that if you do replace your lifters that you replace each set completely (Intake & exaust sets) Dont just replace one or two. All lifters per cam should be replaced at the same time.

Tunes67

Actually I switched from 5W-30 to 10W-30 a year ago. I will try 5W-30 this time. I didn't have this problem before I went for 10W-30. It started since last fall when it was getting cold I guess. Again, thanks for the great info.

I replaced the oil switch last night and that was it. It works perfect now. The part was $20.90 plus tax from the dealership. Oil switch was little hard to reach from underneath of the car. You will need 1/2 foot long extension with deeper socket. That'll do the job. Thanks for all your help guys!!