slow water leak plus P0135, P1131, and P0133 codes

[myf16]

My 1996 Explorer 4WD 4.0L has three check engine codes:
P0135, P1131, and P0133
When I clear them they return fairly quickly.

When I first saw the P0133 code I changed the pre-catalyst oxygen sensor on the right side. Now I have P0133 and two more codes. So I guess it wasn't a problem with the sensor itself.

The water level in the reservoir is dropping slowly, maybe half a gallon per 1000 miles. That might be related if it's a head gasket failure but otherwise it could be a bad radiator cap or a leak in the radiator.

What do you guys think is the problem with my Explorer?

 

[myf16]

I forgot to add: The engine idles smoothly, so I do not suspect a major vacuum leak.

This problem has me baffled.

 

[Torqueranger]

My 1996 Explorer 4WD 4.0L has three check engine codes:
P0135, P1131, and P0133
When I clear them they return fairly quickly.

When I first saw the P0133 code I changed the pre-catalyst oxygen sensor on the right side. Now I have P0133 and two more codes. So I guess it wasn't a problem with the sensor itself.

The water level in the reservoir is dropping slowly, maybe half a gallon per 1000 miles. That might be related if it's a head gasket failure but otherwise it could be a bad radiator cap or a leak in the radiator.

What do you guys think is the problem with my Explorer?

I am not sure about the coolant the leak but check the spark pluggs or something else ... Well your problem is that every code points to bank 1 sensor 1 which is the passenger side of the truck or 1# cylinder

 

[watt9386]

I am not sure about the coolant the leak but check the spark pluggs or something else ... Well your problem is that every code points to bank 1 sensor 1 which is the passenger side of the truck or 1# cylinder

Could the coolant leak have anything to do with it throwing codes? If it fouled up sensors, it could come from a head gasket

Sent from my Nexus 4 using Forum Runner

 

[myf16]

Could the coolant leak have anything to do with it throwing codes? If it fouled up sensors, it could come from a head gasket

Yes, that's what I'm thinking. How does one confirm a head gasket leak? Radiator pressure test? Compression test?

If I have a leak I'm thinking about spending $60 on BlueDevil Head Gasket Sealer which appears to have a decent success probability on slow leaks. After reading this thread I decided not to try retorquing the head bolts.

Or maybe I'll just take the time to pull the head off in my driveway. My mechanic says it's 10 hours to replace both head gaskets, so I figure it's 20 hours if I do it myself.

 

[watt9386]

Yes, that's what I'm thinking. How does one confirm a head gasket leak? Radiator pressure test? Compression test?

If I have a leak I'm thinking about spending $60 on BlueDevil Head Gasket Sealer which appears to have a decent success probability on slow leaks. After reading this thread I decided not to try retorquing the head bolts.

Or maybe I'll just take the time to pull the head off in my driveway. My mechanic says it's 10 hours to replace both head gaskets, so I figure it's 20 hours if I do it myself.

Sent from my Nexus 4 using Forum Runner

 

[watt9386]

Yes, that's what I'm thinking. How does one confirm a head gasket leak? Radiator pressure test? Compression test?

If I have a leak I'm thinking about spending $60 on BlueDevil Head Gasket Sealer which appears to have a decent success probability on slow leaks. After reading this thread I decided not to try retorquing the head bolts.

Or maybe I'll just take the time to pull the head off in my driveway. My mechanic says it's 10 hours to replace both head gaskets, so I figure it's 20 hours if I do it myself.

Do a cylinder leak down test. And I wouldn't mess with the sealer. It just clogs up all the other coolant passages and is a mother to get out later on

Sent from my Nexus 4 using Forum Runner

 

[myf16]

Do a cylinder leak down test.

Is it worth doing the leak-down test at the radiator first, or does the dropping water level pretty much guarantee that there is a leak somewhere in the cooling system?

 

[watt9386]

Is it worth doing the leak-down test at the radiator first, or does the dropping water level pretty much guarantee that there is a leak somewhere in the cooling system?

Well doing the cylinder leak down test will tell you exactly where your head gasket is bad. If you do it and can hear it bubble up in the reservoir, its a head gasket

Sent from my Nexus 4 using Forum Runner

 

[Torqueranger]

what O2 sensor did you replace because you stated that you replaced the right side which would be the driver side or bank 2 ????

 

[myf16]

what O2 sensor did you replace because you stated that you replaced the right side which would be the driver side or bank 2 ????

The right side of the car, in front of the passenger. The sensor was the forwardmost O2 sensor on the passenger side. I kept the old sensor which looked remarkably good and wasn't hard to remove at all. This truck has 115k miles on it.

 

[myf16]

The mechanic says the cooling system tested free of any leaks. So no head gasket replacement for me. Nice.

Now I just have to figure out what could cause those codes despite the fact that I replaced the upstream oxygen sensor on bank 1 and despite the fact that the engine appears to run perfectly. Any ideas?

 

[myf16]

I feel kinda stupid.

The water isn't leaking anymore, if it ever was.

I checked the wire to the O2 sensor and the two halves of the connector separated. Obviously I had not pressed them together fully. It was hard to do one-handed, so I got an assistant to help. Once the connector was seated the problem was fixed. I cleared the codes and they didn't return.

That took much longer than it should have.

FWIW the replacement sensor I used was a Bosch.