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

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

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.