Re: Re: 2000 JGC V-8 overheating/ occasionally only !!
 

On Sun, 17 Dec 2006 08:30:03 -0500, "James" <no one@bellsouth.com>
wrote:

>Sno man, I had been under the impression that a problem with the clutch fan
>would make a car overheat at idle and slow speeds, such as when stopped at a
>red light. Maybe I am thinking about the electric fan though..........
>
>I didn't know they could be adjusted. I will study the site.
>
>Thanks !!
>
>--James--
>

A clutch fan is centrifical and bimetal thermostat controlled. It
engages when the bimetal control lets fluid into clutch disc area
faster than centrifical force can remove it. This is why it can
sometimes cool better at low speed because the centrifical forces are
not purging fluid from it faster than it is being replaced. Also at
low speeds the engine is making less power on average and needs less
cooling generally. When you put a big V8 in a small car the cooling
system has to be just right for it to keep its cool. I would consider
a electric fan as a last resort because it cannot come close to
matching the air flow capabilies of a engine driven clutch fan. To do
so would require more electric power than you vehicle can produce to
sustain it.
-----------------
TheSnoMan.com

Re: Re: 2000 JGC V-8 overheating/ occasionally only !!
 

On Sun, 17 Dec 2006 08:30:03 -0500, "James" <no one@bellsouth.com>
wrote:

>Sno man, I had been under the impression that a problem with the clutch fan
>would make a car overheat at idle and slow speeds, such as when stopped at a
>red light. Maybe I am thinking about the electric fan though..........
>
>I didn't know they could be adjusted. I will study the site.
>
>Thanks !!
>
>--James--
>

A clutch fan is centrifical and bimetal thermostat controlled. It
engages when the bimetal control lets fluid into clutch disc area
faster than centrifical force can remove it. This is why it can
sometimes cool better at low speed because the centrifical forces are
not purging fluid from it faster than it is being replaced. Also at
low speeds the engine is making less power on average and needs less
cooling generally. When you put a big V8 in a small car the cooling
system has to be just right for it to keep its cool. I would consider
a electric fan as a last resort because it cannot come close to
matching the air flow capabilies of a engine driven clutch fan. To do
so would require more electric power than you vehicle can produce to
sustain it.
-----------------
TheSnoMan.com

Re: 2000 JGC V-8 overheating/ occasionally only !!
 

how did u install the t-stat?? backwards i hope not. and look at the radiator
and make sure it is clear of debris esp. in between of the condensor and
radiator

James wrote:

> I posted here about this before, and got some good info.
>
> Symptoms again.......... the car never overheats in town. Does not
> overheat sitting at a redlight.
>
> On the highway, at 70 mph or so, the engine runs about 10-15 degrees
> over what it normally does. Normally, it runs between 190-200 degrees, and
> now runs from 200 to 215 degrees. (Some will say this is normal. Maybe,
> but not for my car. First 120K miles, it ran cooler).
>
> At times, if I go up a long, steep grade, it will overheat rapidly, up to
> 250-260..... it has not been boiling over. If a long steep grade is 2
> miles long, it will heat up like this, and then after the road levels off,
> the engine will cool down to 210 degrees after 2 or 3 miles.
>
> Here is the funny part............ it will not do this every time I go up a
> steep grade. I can do the same grade two times in one day..... same outside
> temperature, and one trip it will run 210 degrees up the hill and on the
> second trip it will almost boil over. So, it is not consistent.
>
> Here is what I have done. New thermostat, 190 degrees. New coolant, and
> flushed radiator. One year ago installed new fan clutch. New serpentine
> drive belt (fan belt)
>
> Jeep has original water pump and radiator. Mileage is 130K. Engine is
> fine.
>
> I am not a mechanic, but I think there are just two main things left. I
> think the water flow is restricted by a clogged or bad radiator, OR I have
> a defect in the water pump.
>
> Questions: How can I diagnose the most probable culprit. the water pump
> or the radiator?
>
> Can't radiator shops do a flow test on the radiator ? Would that test
> also give a hint about the operation of the water pump ?
>
> Are there other possible mechanical problems other than the water pump and
> radiator, given the steps that I have taken already to cure this problem ?
>
> If you had to guess , would you vote for a new water pump or a rod-job or
> new radiator?
>
> Remember two things...... the car NEVER overheats at idle or at slow speed.
> It only overheats at higher speeds, going up steep hills. And, the
> overheating is erratic. The very same conditions/ temp/ road grade/ etc
> will not give the same result each time.
>
> Whaddduuuyaaaa think ??
>
> Thanks !!
>
> --james--

Re: 2000 JGC V-8 overheating/ occasionally only !!
 

how did u install the t-stat?? backwards i hope not. and look at the radiator
and make sure it is clear of debris esp. in between of the condensor and
radiator

James wrote:

> I posted here about this before, and got some good info.
>
> Symptoms again.......... the car never overheats in town. Does not
> overheat sitting at a redlight.
>
> On the highway, at 70 mph or so, the engine runs about 10-15 degrees
> over what it normally does. Normally, it runs between 190-200 degrees, and
> now runs from 200 to 215 degrees. (Some will say this is normal. Maybe,
> but not for my car. First 120K miles, it ran cooler).
>
> At times, if I go up a long, steep grade, it will overheat rapidly, up to
> 250-260..... it has not been boiling over. If a long steep grade is 2
> miles long, it will heat up like this, and then after the road levels off,
> the engine will cool down to 210 degrees after 2 or 3 miles.
>
> Here is the funny part............ it will not do this every time I go up a
> steep grade. I can do the same grade two times in one day..... same outside
> temperature, and one trip it will run 210 degrees up the hill and on the
> second trip it will almost boil over. So, it is not consistent.
>
> Here is what I have done. New thermostat, 190 degrees. New coolant, and
> flushed radiator. One year ago installed new fan clutch. New serpentine
> drive belt (fan belt)
>
> Jeep has original water pump and radiator. Mileage is 130K. Engine is
> fine.
>
> I am not a mechanic, but I think there are just two main things left. I
> think the water flow is restricted by a clogged or bad radiator, OR I have
> a defect in the water pump.
>
> Questions: How can I diagnose the most probable culprit. the water pump
> or the radiator?
>
> Can't radiator shops do a flow test on the radiator ? Would that test
> also give a hint about the operation of the water pump ?
>
> Are there other possible mechanical problems other than the water pump and
> radiator, given the steps that I have taken already to cure this problem ?
>
> If you had to guess , would you vote for a new water pump or a rod-job or
> new radiator?
>
> Remember two things...... the car NEVER overheats at idle or at slow speed.
> It only overheats at higher speeds, going up steep hills. And, the
> overheating is erratic. The very same conditions/ temp/ road grade/ etc
> will not give the same result each time.
>
> Whaddduuuyaaaa think ??
>
> Thanks !!
>
> --james--

Re: 2000 JGC V-8 overheating/ occasionally only !!
 

how did u install the t-stat?? backwards i hope not. and look at the radiator
and make sure it is clear of debris esp. in between of the condensor and
radiator

James wrote:

> I posted here about this before, and got some good info.
>
> Symptoms again.......... the car never overheats in town. Does not
> overheat sitting at a redlight.
>
> On the highway, at 70 mph or so, the engine runs about 10-15 degrees
> over what it normally does. Normally, it runs between 190-200 degrees, and
> now runs from 200 to 215 degrees. (Some will say this is normal. Maybe,
> but not for my car. First 120K miles, it ran cooler).
>
> At times, if I go up a long, steep grade, it will overheat rapidly, up to
> 250-260..... it has not been boiling over. If a long steep grade is 2
> miles long, it will heat up like this, and then after the road levels off,
> the engine will cool down to 210 degrees after 2 or 3 miles.
>
> Here is the funny part............ it will not do this every time I go up a
> steep grade. I can do the same grade two times in one day..... same outside
> temperature, and one trip it will run 210 degrees up the hill and on the
> second trip it will almost boil over. So, it is not consistent.
>
> Here is what I have done. New thermostat, 190 degrees. New coolant, and
> flushed radiator. One year ago installed new fan clutch. New serpentine
> drive belt (fan belt)
>
> Jeep has original water pump and radiator. Mileage is 130K. Engine is
> fine.
>
> I am not a mechanic, but I think there are just two main things left. I
> think the water flow is restricted by a clogged or bad radiator, OR I have
> a defect in the water pump.
>
> Questions: How can I diagnose the most probable culprit. the water pump
> or the radiator?
>
> Can't radiator shops do a flow test on the radiator ? Would that test
> also give a hint about the operation of the water pump ?
>
> Are there other possible mechanical problems other than the water pump and
> radiator, given the steps that I have taken already to cure this problem ?
>
> If you had to guess , would you vote for a new water pump or a rod-job or
> new radiator?
>
> Remember two things...... the car NEVER overheats at idle or at slow speed.
> It only overheats at higher speeds, going up steep hills. And, the
> overheating is erratic. The very same conditions/ temp/ road grade/ etc
> will not give the same result each time.
>
> Whaddduuuyaaaa think ??
>
> Thanks !!
>
> --james--

Re: 2000 JGC V-8 overheating/ occasionally only !!
 

I had this EXACT problem 10 years ago with a Ford vehicle.

Problem: clogged radiator. After replacement, heat was never a problem
again.

Re: 2000 JGC V-8 overheating/ occasionally only !!
 

I had this EXACT problem 10 years ago with a Ford vehicle.

Problem: clogged radiator. After replacement, heat was never a problem
again.

Re: 2000 JGC V-8 overheating/ occasionally only !!
 

I had this EXACT problem 10 years ago with a Ford vehicle.

Problem: clogged radiator. After replacement, heat was never a problem
again.

Re: 2000 JGC V-8 overheating/ occasionally only !!
 

spin the fan while it is cold and if there is a drag on the fan then it is ok

SnoMan wrote:

> On Sat, 16 Dec 2006 21:10:26 -0500, "James" <no one@bellsouth.com>
> wrote:
>
> >Remember two things...... the car NEVER overheats at idle or at slow speed.
> >It only overheats at higher speeds, going up steep hills. And, the
> >overheating is erratic. The very same conditions/ temp/ road grade/ etc
> >will not give the same result each time.
> >
> >Whaddduuuyaaaa think ??
>
> My nickle is on the clutch fan. I know it was replaced 1 year ago but
> I strongly suspect that is is the culprit here. Its engagement temp is
> too high and thats why sometimes it cools and sometimes not. Ram air a
> lone will not always cool the engine especailly a V8 in a GC because
> it is a tight fit. At the link below you will find instruction on have
> to tweak the adjustment of a clutch fan because most of the time a
> little twaeking will cure them.
>
> http://forum.snoman.com/viewtopic.php?t=79
> -----------------
> TheSnoMan.com

Re: 2000 JGC V-8 overheating/ occasionally only !!
 

spin the fan while it is cold and if there is a drag on the fan then it is ok

SnoMan wrote:

> On Sat, 16 Dec 2006 21:10:26 -0500, "James" <no one@bellsouth.com>
> wrote:
>
> >Remember two things...... the car NEVER overheats at idle or at slow speed.
> >It only overheats at higher speeds, going up steep hills. And, the
> >overheating is erratic. The very same conditions/ temp/ road grade/ etc
> >will not give the same result each time.
> >
> >Whaddduuuyaaaa think ??
>
> My nickle is on the clutch fan. I know it was replaced 1 year ago but
> I strongly suspect that is is the culprit here. Its engagement temp is
> too high and thats why sometimes it cools and sometimes not. Ram air a
> lone will not always cool the engine especailly a V8 in a GC because
> it is a tight fit. At the link below you will find instruction on have
> to tweak the adjustment of a clutch fan because most of the time a
> little twaeking will cure them.
>
> http://forum.snoman.com/viewtopic.php?t=79
> -----------------
> TheSnoMan.com