96 Mazda Protege

Tiny
URDEEPESTREALITY
  • MEMBER
  • 1996 MAZDA PROTEGE
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 116 MILES
I need some help. My car overheated when a friend of mine failed to put my radiator cap on correctly. I ended up losing all the fluid in my cooling system and let it cool before refilling it. It started to overheat a few more times and I had to bleed the air out of the radiator. Then the engine started misfiring occasionally when starting up and the temp gauge sometimes creeps up at long idles. Thought maybe there was still air in there and just keep trying to bleed the system. So I replaced the radiator cap, and got a thermostat and spark plugs/wires put on my car. And the temp gauge seemed like it was going up less frequently. But then 2 days ago the check engine light came on. And the temp gauge still sometimes creeps up on long idles. Also I can smell burning coolant. I fill up my coolant regularly but when I check my coolant level after driving heavily there are bubbles in the coolant. But once it cools down its low again. Its really frustrating. So I got the codes read and they are PO115 and PO420 help please!
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Saturday, August 13th, 2011 AT 11:53 PM

14 Replies

Tiny
RASMATAZ
  • MEMBER
If I were you have it chemically and pressure tested-start here
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Sunday, August 14th, 2011 AT 12:13 AM
Tiny
CARADIODOC
  • EXPERT
Sounds like you have a leaking head gasket all along. You should not have to be adding coolant "regularly".

The chemical test rasmatz is talking about involves drawing air from the radiator through a glass cylinder with two chambers partially filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow. A leaking head gasket will allow exhaust gas to be pushed into the cooling system and coolant to be burned in the engine and disappear out the tail pipe.

That air can also pool under the thermostat allowing it to close, and the engine to overheat. Thermostats open in response to hot liquid. They don't respond to hot air.
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Sunday, August 14th, 2011 AT 1:01 AM
Tiny
URDEEPESTREALITY
  • MEMBER
I was told by a couple people that if it were the head gasket there would be white smoke coming out the tail pipe, which there is none, or coolant in my oil or vice versa, which there is none. What do those codes mean?
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Sunday, August 14th, 2011 AT 5:56 AM
Tiny
CARADIODOC
  • EXPERT
P0115 Engine Coolant Temperature Circuit Malfunction

P0420 Catalyst System Efficiency Below Threshold (Bank 1)
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Sunday, August 14th, 2011 AT 6:20 AM
Tiny
URDEEPESTREALITY
  • MEMBER
Is it possible to try to determine what is most likely setting the codes off?
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Sunday, August 14th, 2011 AT 6:32 AM
Tiny
CARADIODOC
  • EXPERT
Not easily. Codes get you to the circuit that needs diagnosis, not usually to the defective part.

Coolant sensors don't fail real often. More common is a loose connector, the connector was removed while the ignition switch was turned on, or a terminal in the connector is stretched and making intermittent contact. The most effective way to troubleshoot them is with a scanner that displays live data.

The rear oxygen sensor monitors what comes out of the catalytic converter. The front one monitors what goes in. By those sensor readings, the Engine Computer knows what the converter is doing. When it's not cleaning up the exhaust properly, it turns on the Check Engine light. Most of the time that means a new converter is needed, but other tests should be done first to confirm that.
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Sunday, August 14th, 2011 AT 6:51 AM
Tiny
URDEEPESTREALITY
  • MEMBER
I'll try to get some tests done. I forgot to mention another weird occurance. When I turn the heater on and off, I hear a weird noise coming from the dash. Kind of a winding down noise or something, almost sounds like fluid? I can't really describe it well.
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Monday, August 15th, 2011 AT 6:27 AM
Tiny
CARADIODOC
  • EXPERT
How about the heater fan motor coming to a stop?
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Monday, August 15th, 2011 AT 6:34 AM
Tiny
URDEEPESTREALITY
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No the heater works fine. Its just when I turn it off it makes an odd gurgling noise. But I just talked to the mechanic and asked if he ran a pressure test when they changed the thermostat and he said they did, and everything tested fine. So I have an appointment to have them check it out tomorrow. Hopefully he figures out what the problem is.
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Monday, August 15th, 2011 AT 8:21 PM
Tiny
CARADIODOC
  • EXPERT
Perhaps air in the heater core? Radiator fan coasting to a stop? Keep us posted.
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Monday, August 15th, 2011 AT 11:11 PM
Tiny
URDEEPESTREALITY
  • MEMBER
The guy said the best place to start would be temp switch/sender and the o2 sensor. He didnt put any scanner or anything to it though. Just hooked the computer up. Should a take it to a different mechanic? Or get the o2 sensor and temp switch and have them done?
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Tuesday, August 16th, 2011 AT 8:35 PM
Tiny
CARADIODOC
  • EXPERT
The coolant temperature sensor should be tested with a simple ohm meter reading before it's replaced. Any goofball can replace parts. Professionals do at least a little testing first to be sure the new parts are needed. If the initial problem started from leaving the radiator cap loose, that's not going to damage the coolant temperature sensor. I suspect someone just unplugged it at one time. Erase the fault codes and see if they come back before replacing parts.

The downstream, (after the catalytic converter), O2 sensor is just reporting what it sees, so changing it isn't going to fix a problem with the converter. Again, see if that code comes back after it's erased.

To erase the codes yourself, disconnect the negative battery cable for a minute, then reconnect it. Don't do this on newer cars because many computers can lock up and will need to be reprogrammed by the dealer. I have to mention that for the benefit of other people who might read this and try it. General Motors and Volkswagen are the worst offenders at that. They are very good at getting your money after the sale.
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Tuesday, August 16th, 2011 AT 9:03 PM
Tiny
URDEEPESTREALITY
  • MEMBER
Well the intial problems started after my radiator cap popped off and blew all of the fluid out of my cooling system on a long distance drive. Yeah I was thinking of getting a quote from another shop because I feel like being a women these mechanics all try to rip me off.
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Tuesday, August 16th, 2011 AT 10:31 PM
Tiny
CARADIODOC
  • EXPERT
I've heard that many times before, but more often than not, it's not that you're a women; it's that you don't speak the same language as mechanics. The same can be said of 90 percent of men. As a former instructor at a community college, I was asked almost every week by someone to examine their repair bill, and when it was explained in layman's terms, people realized what at first appeared to be excessive charges was really the mechanic looking out for the customer in the long run.

Many mechanics never even meet the car owner. They just diagnose the problem, then report their findings to the service adviser who contacts the owner with various repair options. Service advisers often don't know much about cars, but they have good communication skills; something most mechanics lack.

We spent a lot of time in my classes too on "perception". A shady salesman for any product can make you feel good while ripping you off. THOSE are the people who give every profession a bad reputation. The honest people in any profession don't make news. We never hear about them.

I felt just the opposite about woman customers when I worked for a very nice Chrysler dealership. I made an effort to do extra things at no charge and to keep costs down to help prove we could be trusted. We had a REAL big base of repeat customers, both for service and new car sales. I was lucky that I often got to meet the owners and talk with them. I explained what their car needed right now and what could wait. We were always so busy, there was no need to try to pad the bill by selling unneeded services. Some shops are slow so they look harder for other things to sell you. That's okay if a preventive service makes your car last longer, but it should really be needed.

We fall into a rut when we explain the same things over and over so we start to leave things out, or we forget you're hearing this for the first time. I've heard mechanics tell a customer what was needed to fix their car, and the way they said it, I wouldn't even approve the service. They are busy and have other cars waiting, and they describe the problem and cure as though they were talking with another mechanic. A good doctor will explain things a lot differently to the patient than to another doctor. Doctors, and mechanics, who are wrapped up in their work, forget or don't want to take the time to explain things in detail. They just blurt out the repair and the cost, and expect you to make an instant, informed decision when you don't have all information. That can lead to the customer's lack of confidence in the mechanic.

The best thing you can do is ask some questions when presented with their findings. Ask if what they found could have caused other problems that might not show up right away. If they give you various choices such as replacing a large component vs. Rebuilding it on site, ask for the advantages and disadvantages each way, and what they would do if it was their car. They might have their own recommendations too. Many repairs involve parts that come as complete assemblies or as individual parts. The individual parts cost much less but take a lot more time to install. Complete assemblies cost more and were assembled in a controlled factory environment, but take less labor time to install. If business is slow, they may opt for the less expensive parts that take more time to install. The overall cost to you might be about the same but it will keep the mechanic busy. If the shop has a lot of people waiting, they will likely steer you toward the complete assembly to save time so they can move on to the next car. Most shops are busy now because people are fixing older cars rather than buying new ones. If you see one shop that has people standing around, there might be a reason. Look for a busy one.

Sorry to get so far off topic. Once I get on a roll, I can't stop.
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Wednesday, August 17th, 2011 AT 10:30 PM

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