O2 sensor code - coolant smell & strange happenings

[Snoworks]

OK - First this is not for a chevy vehical, but not alot of people are reading or answering questions in the SUV forum!

Its a 1999 Jeep with a 4.0. I believe some of my questions can be answered by anyone with auto experience regardless of make!

First the truck is pulling up the following code: O2 sensor heater circuit malfuntion

Secondly the radiator is not building up any pressure when hot, even though the truck reads that the temp is ok(or 210). The strange thing is when I take the cap of the radiator, first no pressure, 2nd very limited flow of coolant running through the motor that I can see. Maybee no flow, because the fluid level is right at the cap level, and it barely moves if I give the truck gas. There is definately very limited flow, because the fluid just goes up and down maybee an 1/2" or so, with no circulation.

Their is also the hint of antifreeze smell, but no leakage in the past two days, that has feel to the ground.

Any suggestions, I am stumpped with the no flow issue, yet the truck is not overheating!!!!!!!!!

Chuck B.

[Snoworks]

Temps on the colant go down from 204-210 to about 195-199 when I give the truck gas, when monitoring in the scan tool.

Thought this might give a little more insight.

Chuck B.

[phoenix827]

Huh! Similar to my S10!
I have the same smell froma a VERY slow leak in the heater core area.
BUT, No matter what I do, the temp gauge never comes up very hi.
I Also have a bad O2 sensor i NEED to torch out, but haven't gotten to it.
Sounds to me like you might have something blocking the flow, but I would think the temps would go higher.

[wyldman]

The coolant temps are pretty much normally,when you rev the engine it's normal for the coolant temps to drop.

The coolant smell may be a small leak.Check the heater hoses at the front of the engine,they like to split there.They also like to leak at the back,as there are a lot of connections and crimps there too.

It could be the rad too,but's it kinda hard to see,as it's very tight and tucked up in the front.

You may want to use a pressure tester,it may make it easier to find your leak.

The O2 sensor malfunction sounds like just a bad 02.Make sure there is no oil leaking on the sensor,as that can kill the heater circuit.

[Snoworks]

When the truck is hot, the radiator does not have any pressure build up. Is this normal?

I think I found the radiator leak. I found fluid running out between the top section of the radiator, and the main fan coil section. On these vehicals, the top section is just set on top of the main section and then metal tabs are crimpped over to hold them together. There is no welds, etc. It seems to be leaking from this area. Kind of a weak design IMO.

Chuck B.

[festerw]

Try replacing the radiator cap, then see if builds pressure. On the O2 sensor have you ever replaced it, it's recommended every 60,000, and believe it or not the Jeep dealer may be cheaper than the parts store for one.

[wyldman]

The newer style rads use a gasket to seal the tank to the core,and the core is then crimped over the tank to hold it in place.The gaskets will start to leak over time,and you will need to replace them,or recore the rad.It may even be cheaper to get a new rad instead,and most come with lifetime warranties.

Installing a new rad cap when repairing the rad would be a good idea too.

[Snoworks]

I used some stop leak to see if it seals it. If it does, I will wait until spring to replace the radiator. My repair bills for this season, have been quite high. Every year, I seem to spend more and more on repairs.

Chuck B.