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Jeep Overheating
Hi all,
I recently purchased a '95 Jeep Cherokee 4x4. Everything seems to be in perfect condition however, I have an odd overheating issue. While driving in "mild" traffic (usually at low speeds) it tends to overheat slightly. The gauge never reaches critical (red) and when I get back to normal driving speeds everything goes back to normal. I checked the fan and its fine. I checked the coolant and oil - both are new and I can find absolutely no leaks. And its not burning oil at all. Oddly enough, during these periods of overheating the A/C compressor seems to stop working and I hear a knocking when accelerating. Haven't checked out the water pump or thermostat yet. Any suggestions/ideas? TIA, TJ |
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#2
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tj wrote:
> > Hi all, > > I recently purchased a '95 Jeep Cherokee 4x4. Everything seems to be > in perfect condition however, I have an odd overheating issue. While > driving in "mild" traffic (usually at low speeds) it tends to overheat > slightly. The gauge never reaches critical (red) and when I get back > to normal driving speeds everything goes back to normal. I checked the > fan and its fine. I checked the coolant and oil - both are new and I > can find absolutely no leaks. And its not burning oil at all. Oddly > enough, during these periods of overheating the A/C compressor seems > to stop working and I hear a knocking when accelerating. Haven't > checked out the water pump or thermostat yet. What sort of fan on on the engine? Is it a rigid fan, or some sort of fluid coupline (fan clutch) or is it electric? Usually slow speed overheating is related to the fan and fan clutch (if so equipped) since its the fan's job to pull enough air through the radiator to cool the engine at slow speeds. At higher speeds, the vehicle's motion through the air is usually sufficient to keep enough air flow through the radiator to cool the engine. -- Roger |
#3
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tj proclaimed:
> Hi all, > > I recently purchased a '95 Jeep Cherokee 4x4. Everything seems to be > in perfect condition however, I have an odd overheating issue. While > driving in "mild" traffic (usually at low speeds) it tends to overheat > slightly. The gauge never reaches critical (red) and when I get back > to normal driving speeds everything goes back to normal. I checked the > fan and its fine. I checked the coolant and oil - both are new and I > can find absolutely no leaks. And its not burning oil at all. Oddly > enough, during these periods of overheating the A/C compressor seems > to stop working and I hear a knocking when accelerating. Haven't > checked out the water pump or thermostat yet. If the engine is truly getting hot enough that it is knocking, this is not at all good and can get expensive. I strongly would not recommend continuing to drive it in this condition as you can warp the thing...and it may be too late. The temperature guage itself has been known to be a problem on that thing, but if you get knocking and A/C shutoff, the engine has detected in multiple ways that it is too hot. The 4.0 I-6 doesn't normally have overheat problems even in desert temperatures. The radiator and cooling system are sufficiently oversized they can usually cool the engine even with a marginal water pump. When you say you checked the fan, how did you check it? That thing should begin howling like a banshee as soon as the temp guage gets much over 190 and the rpm goes up. If you don't hear the fan making a rather loud whirring as the engine heats up, that fan is bad. Loose serpentine can cause overheating. Normal tightness is quite a bit higher than most fan belts--should be virtually zero deflection. Bad fan clutch can cause overheating. And is the most common cause of low speed overheat. Replacing the water pump with the wrong rotation version can cause overheating--there are two types and a common mistake by non-jeep mechanics is to put in the backwards one. |
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