noob questions

[firestarter]

Hi everyone. I just became a member and am hoping that I can get some insight into what is going on with my 2000 XJ. I bought it not too long ago with about 54,000 miles (currently has 103,000) and here are a few issues it has which I can't seem to figure out. I should mention that this jeep is stock.

1.) It has an erratic idle which "pulses" about ever 30secs, each time the rpm's jump about 250/400. For a while it would become very erratic then die so i replaced the IAC unit (OEM part) and it doesn't die anymore but still contains with weird idle. When the engine is hot it almost sounds like a valve it opening/closing.

2.) I am losing coolant and cannot explain where it's going :-( Not rapidly, but am losing more fluid than I would expect.

3.) When driving on the highway, occasionally, the oil pressure gauge will hit the max. If i ease off of the throttle for a while it goes back to normal. During this time the engine doesn't make any other sounds, everything seems normal. Maybe just a bad sensor? I should mention that if my coolant is at the "add" level this doesn't occur. I know that sounds strange and might just be a coincidence but I thought I should mention it.

4.) After the engine is hot and parked or idle at a light I can hear a bubbling noise from the engine. If I ease off the brake and gently apply the brake it seems to go away.

Thanks in advance,

 

[SteelHeadz]

Welcome to Jeepz. First things first. Find the coolant leak. I'm concerned that the coolant leak is internal if you don't find it leaking outside anywhere. Have you checked the engine oil condition? Milky in color?, the bubbling noise is possibly an overheat issue. I would seriously have the head gasket and the cylinder head checked for coolant leak if the leak is not externally isolated.

 

[firestarter]

Thank you. Seems to be a great wealth of knowledge on these forums. My dad also suggested checking for "milky oil" but that doesn't seem to be the case. The oil seems perfectly fine to me. As far as the bubbling noise goes, you mention it's an overheat issue. What exactly do you mean by that, is it something i can remedy?

Thanks,

 

[MudderChuck]

I was also thinking a possible head gasket leak. But before you skip any steps you really have to inspect for external leaks. Some good hiding spots are the top of the bottom radiator hose where it connects to the water pump, under the fan shroud in the upper right hand corner often (battery side), the water pump weep hole (from a shaft seal leak). Some of these leaks can be small and much of the coolant can evaporate before it ever hits the ground. Long term leaks often leave a whitish crust around the leak, looks almost like mold. A flashlight and a small mirror can be helpfull, some spots are almost impossible to see like the weep hole.
Head gaskets can leak both directions, exhaust gases get into the cooling system and coolant comes out of the exhaust.
You can sometime sniff the coolant bottle and detect an exhaust odor. You can collect some of the condensation that comes out of the exhaust, at cold start up, on a white paper towel and see if it has a tint that matches your coolant color. Not difinitve tests, but good indicators of a head gasket leak.
The cooling system is designed to keep on cooling after the motor is shut down, by convection (hot fluids rise, colder fluids sink). Some gurgling noise can be the convection, some may be a lack of convection due to air or exhaust bubbles/blocks in the system that don't allow convection. The coolant can get pretty hot at certain spots inside the motor, without the convection and may start to boil (which can also add to the air blockage problem).
The system is designed to expel a little coolant into the coolant bottle after it reaches a certain pressure from expansion, during normal operation. There is a valve in the cap to allow this. When the motor is shut off and the coolant contracts as it cools down, the valving in the cap allows coolant to be sucked back into the radiator from the coolant bottle (that's why it's often called a coolant recovery bottle or reservoir).

 

[firestarter]

Okay, so I had some time to look at this yesterday and I think I have rather good news. After wiping everything down, cleaning up all areas around hoses, etc .. then running the vehicle for a while I found a very small leak on the bottom right of the radiator (facing the vehicle). I checked the run-off from the exhaust and it's crystal clear and the overflow tank doesn't smell like exhaust. So thats all good, just a small leak. However, I still get the bubbling noise when the engine is at idle temp (210). If this is due to a bubble in the line it seems like this would go away when i replace the radiator?

On a side note, while inspecting the engine it seems like the clutch on the AC condensor is kicking pretty hard which I don't remember it being so loud. Do you think i need a recharge for the AC or is it possible that the clutch is wearing down, therefore, causing it to travel more before it kicks in?

As far as replacing the radiator goes, it currently has plastic sides, is it possible to get one with metal sides. Or something that is more robust in general?

Thanks again,

 

[SteelHeadz]

Okay, so I had some time to look at this yesterday and I think I have rather good news. After wiping everything down, cleaning up all areas around hoses, etc .. then running the vehicle for a while I found a very small leak on the bottom right of the radiator (facing the vehicle). I checked the run-off from the exhaust and it's crystal clear and the overflow tank doesn't smell like exhaust. So thats all good, just a small leak. However, I still get the bubbling noise when the engine is at idle temp (210). If this is due to a bubble in the line it seems like this would go away when i replace the radiator?



Theoretically speaking, yes it should fix the bubbling sound . 210* is only 2* from the boiling point. I would replace the T-stat to a colder temp though.

On a side note, while inspecting the engine it seems like the clutch on the AC condensor is kicking pretty hard which I don't remember it being so loud. Do you think i need a recharge for the AC or is it possible that the clutch is wearing down, therefore, causing it to travel more before it kicks in?

A/C compressors always have been a hard knock when it engages. Depending on your definition, if it's cycling too often, then it's likely the freon is low, however, consider the cooling system temperature as a variable. The head pressure increases as the condenser temperature rises due to a hotter than normal radiator. The hi and lo pressure transducer plays a big role on this varying pressures as to turn on or off the A/C clutch. I recommend you repair the radiator issue first and re-diagnose the a/c compressor.



As far as replacing the radiator goes, it currently has plastic sides, is it possible to get one with metal sides. Or something that is more robust in general?

The only ones i know thats manufactured in a rigid form is an aluminum radiator. I have been running mine with the Flowkooler aluminum radiator and a high flow water pump with no issues. It's solid all the way around with no crimps.

Thanks again,

I hope this helps.