91 YJ Heater problem
 

91 YJ 4.0 (125k miles, no AC)

While driving home from work yesterday I noticed the heater was blowing
cold air only. This may have started several days ago but I really
didn't notice. I watched the temp and it remained consistant (210 +-3
degrees).

This morning on the way to work I was ultra paranoid about the temp. I
noticed at highway speed it was normal, but at highway stop lights (2
min) it would creep up (+10 degrees). Once I got moving again the temp
would go back to normal.

At the office I checked the coolant level and found it to be low (I
could see it at the bottom of the resv). At luch I went out to get
some coolant and magically the heater was working fine. After driving
the Jeep to normal operating temp, I idled for 20 min without
experiencing a large jump in the temperature.

Would anything other then a block in the heater core cause the lose of
heat? Would a blocked heater core cause the temp to fluxuate as
described?

When adding less then a gallon of coolant, can I use water only? I had
the water pump changed last winter, and I don't know what type of
coolant was used. Can I just match colors?

Thanks for the help.

CTM

Re: 91 YJ Heater problem
 

Your radiator is low on coolant. You need to use a mix to top it up.
You are pretty safe with the same color I think. Top up the rad first,
then top up the overflow to be sure the rad still doesn't have air
inside.

You are describing low coolant in the rad with the temp changes.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

"testert555@gmail.com" wrote:
>
> 91 YJ 4.0 (125k miles, no AC)
>
> While driving home from work yesterday I noticed the heater was blowing
> cold air only. This may have started several days ago but I really
> didn't notice. I watched the temp and it remained consistant (210 +-3
> degrees).
>
> This morning on the way to work I was ultra paranoid about the temp. I
> noticed at highway speed it was normal, but at highway stop lights (2
> min) it would creep up (+10 degrees). Once I got moving again the temp
> would go back to normal.
>
> At the office I checked the coolant level and found it to be low (I
> could see it at the bottom of the resv). At luch I went out to get
> some coolant and magically the heater was working fine. After driving
> the Jeep to normal operating temp, I idled for 20 min without
> experiencing a large jump in the temperature.
>
> Would anything other then a block in the heater core cause the lose of
> heat? Would a blocked heater core cause the temp to fluxuate as
> described?
>
> When adding less then a gallon of coolant, can I use water only? I had
> the water pump changed last winter, and I don't know what type of
> coolant was used. Can I just match colors?
>
> Thanks for the help.
>
> CTM

Re: 91 YJ Heater problem
 

Your radiator is low on coolant. You need to use a mix to top it up.
You are pretty safe with the same color I think. Top up the rad first,
then top up the overflow to be sure the rad still doesn't have air
inside.

You are describing low coolant in the rad with the temp changes.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

"testert555@gmail.com" wrote:
>
> 91 YJ 4.0 (125k miles, no AC)
>
> While driving home from work yesterday I noticed the heater was blowing
> cold air only. This may have started several days ago but I really
> didn't notice. I watched the temp and it remained consistant (210 +-3
> degrees).
>
> This morning on the way to work I was ultra paranoid about the temp. I
> noticed at highway speed it was normal, but at highway stop lights (2
> min) it would creep up (+10 degrees). Once I got moving again the temp
> would go back to normal.
>
> At the office I checked the coolant level and found it to be low (I
> could see it at the bottom of the resv). At luch I went out to get
> some coolant and magically the heater was working fine. After driving
> the Jeep to normal operating temp, I idled for 20 min without
> experiencing a large jump in the temperature.
>
> Would anything other then a block in the heater core cause the lose of
> heat? Would a blocked heater core cause the temp to fluxuate as
> described?
>
> When adding less then a gallon of coolant, can I use water only? I had
> the water pump changed last winter, and I don't know what type of
> coolant was used. Can I just match colors?
>
> Thanks for the help.
>
> CTM

Re: 91 YJ Heater problem
 

Your radiator is low on coolant. You need to use a mix to top it up.
You are pretty safe with the same color I think. Top up the rad first,
then top up the overflow to be sure the rad still doesn't have air
inside.

You are describing low coolant in the rad with the temp changes.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

"testert555@gmail.com" wrote:
>
> 91 YJ 4.0 (125k miles, no AC)
>
> While driving home from work yesterday I noticed the heater was blowing
> cold air only. This may have started several days ago but I really
> didn't notice. I watched the temp and it remained consistant (210 +-3
> degrees).
>
> This morning on the way to work I was ultra paranoid about the temp. I
> noticed at highway speed it was normal, but at highway stop lights (2
> min) it would creep up (+10 degrees). Once I got moving again the temp
> would go back to normal.
>
> At the office I checked the coolant level and found it to be low (I
> could see it at the bottom of the resv). At luch I went out to get
> some coolant and magically the heater was working fine. After driving
> the Jeep to normal operating temp, I idled for 20 min without
> experiencing a large jump in the temperature.
>
> Would anything other then a block in the heater core cause the lose of
> heat? Would a blocked heater core cause the temp to fluxuate as
> described?
>
> When adding less then a gallon of coolant, can I use water only? I had
> the water pump changed last winter, and I don't know what type of
> coolant was used. Can I just match colors?
>
> Thanks for the help.
>
> CTM

Re: 91 YJ Heater problem
 

A low coolant level will almost always result in poor or no heat output.

If you have American Green then you can, most likely just top it off with a
50/50 mix. Do Not just use water.

What color coolant do you have?


<testert555@gmail.com> wrote in message
news:1136493497.626621.47840@g44g2000cwa.googlegro ups.com...
> 91 YJ 4.0 (125k miles, no AC)
>
> While driving home from work yesterday I noticed the heater was blowing
> cold air only. This may have started several days ago but I really
> didn't notice. I watched the temp and it remained consistant (210 +-3
> degrees).
>
> This morning on the way to work I was ultra paranoid about the temp. I
> noticed at highway speed it was normal, but at highway stop lights (2
> min) it would creep up (+10 degrees). Once I got moving again the temp
> would go back to normal.
>
> At the office I checked the coolant level and found it to be low (I
> could see it at the bottom of the resv). At luch I went out to get
> some coolant and magically the heater was working fine. After driving
> the Jeep to normal operating temp, I idled for 20 min without
> experiencing a large jump in the temperature.
>
> Would anything other then a block in the heater core cause the lose of
> heat? Would a blocked heater core cause the temp to fluxuate as
> described?
>
> When adding less then a gallon of coolant, can I use water only? I had
> the water pump changed last winter, and I don't know what type of
> coolant was used. Can I just match colors?
>
> Thanks for the help.
>
> CTM
>

Re: 91 YJ Heater problem
 

A low coolant level will almost always result in poor or no heat output.

If you have American Green then you can, most likely just top it off with a
50/50 mix. Do Not just use water.

What color coolant do you have?


<testert555@gmail.com> wrote in message
news:1136493497.626621.47840@g44g2000cwa.googlegro ups.com...
> 91 YJ 4.0 (125k miles, no AC)
>
> While driving home from work yesterday I noticed the heater was blowing
> cold air only. This may have started several days ago but I really
> didn't notice. I watched the temp and it remained consistant (210 +-3
> degrees).
>
> This morning on the way to work I was ultra paranoid about the temp. I
> noticed at highway speed it was normal, but at highway stop lights (2
> min) it would creep up (+10 degrees). Once I got moving again the temp
> would go back to normal.
>
> At the office I checked the coolant level and found it to be low (I
> could see it at the bottom of the resv). At luch I went out to get
> some coolant and magically the heater was working fine. After driving
> the Jeep to normal operating temp, I idled for 20 min without
> experiencing a large jump in the temperature.
>
> Would anything other then a block in the heater core cause the lose of
> heat? Would a blocked heater core cause the temp to fluxuate as
> described?
>
> When adding less then a gallon of coolant, can I use water only? I had
> the water pump changed last winter, and I don't know what type of
> coolant was used. Can I just match colors?
>
> Thanks for the help.
>
> CTM
>

Re: 91 YJ Heater problem
 

A low coolant level will almost always result in poor or no heat output.

If you have American Green then you can, most likely just top it off with a
50/50 mix. Do Not just use water.

What color coolant do you have?


<testert555@gmail.com> wrote in message
news:1136493497.626621.47840@g44g2000cwa.googlegro ups.com...
> 91 YJ 4.0 (125k miles, no AC)
>
> While driving home from work yesterday I noticed the heater was blowing
> cold air only. This may have started several days ago but I really
> didn't notice. I watched the temp and it remained consistant (210 +-3
> degrees).
>
> This morning on the way to work I was ultra paranoid about the temp. I
> noticed at highway speed it was normal, but at highway stop lights (2
> min) it would creep up (+10 degrees). Once I got moving again the temp
> would go back to normal.
>
> At the office I checked the coolant level and found it to be low (I
> could see it at the bottom of the resv). At luch I went out to get
> some coolant and magically the heater was working fine. After driving
> the Jeep to normal operating temp, I idled for 20 min without
> experiencing a large jump in the temperature.
>
> Would anything other then a block in the heater core cause the lose of
> heat? Would a blocked heater core cause the temp to fluxuate as
> described?
>
> When adding less then a gallon of coolant, can I use water only? I had
> the water pump changed last winter, and I don't know what type of
> coolant was used. Can I just match colors?
>
> Thanks for the help.
>
> CTM
>

Re: 91 YJ Heater problem
 

your core could be clogged. unhook both hoses going to the heater core, at
the engine side, and stick a garden hose on the side where the coolent flows
back to the engine. Turn on the hose and watch your core cough up some
horrible junk! Your all set now...
Nick

<testert555@gmail.com> wrote in message
news:1136493497.626621.47840@g44g2000cwa.googlegro ups.com...
> 91 YJ 4.0 (125k miles, no AC)
>
> While driving home from work yesterday I noticed the heater was blowing
> cold air only. This may have started several days ago but I really
> didn't notice. I watched the temp and it remained consistant (210 +-3
> degrees).
>
> This morning on the way to work I was ultra paranoid about the temp. I
> noticed at highway speed it was normal, but at highway stop lights (2
> min) it would creep up (+10 degrees). Once I got moving again the temp
> would go back to normal.
>
> At the office I checked the coolant level and found it to be low (I
> could see it at the bottom of the resv). At luch I went out to get
> some coolant and magically the heater was working fine. After driving
> the Jeep to normal operating temp, I idled for 20 min without
> experiencing a large jump in the temperature.
>
> Would anything other then a block in the heater core cause the lose of
> heat? Would a blocked heater core cause the temp to fluxuate as
> described?
>
> When adding less then a gallon of coolant, can I use water only? I had
> the water pump changed last winter, and I don't know what type of
> coolant was used. Can I just match colors?
>
> Thanks for the help.
>
> CTM
>

Re: 91 YJ Heater problem
 

your core could be clogged. unhook both hoses going to the heater core, at
the engine side, and stick a garden hose on the side where the coolent flows
back to the engine. Turn on the hose and watch your core cough up some
horrible junk! Your all set now...
Nick

<testert555@gmail.com> wrote in message
news:1136493497.626621.47840@g44g2000cwa.googlegro ups.com...
> 91 YJ 4.0 (125k miles, no AC)
>
> While driving home from work yesterday I noticed the heater was blowing
> cold air only. This may have started several days ago but I really
> didn't notice. I watched the temp and it remained consistant (210 +-3
> degrees).
>
> This morning on the way to work I was ultra paranoid about the temp. I
> noticed at highway speed it was normal, but at highway stop lights (2
> min) it would creep up (+10 degrees). Once I got moving again the temp
> would go back to normal.
>
> At the office I checked the coolant level and found it to be low (I
> could see it at the bottom of the resv). At luch I went out to get
> some coolant and magically the heater was working fine. After driving
> the Jeep to normal operating temp, I idled for 20 min without
> experiencing a large jump in the temperature.
>
> Would anything other then a block in the heater core cause the lose of
> heat? Would a blocked heater core cause the temp to fluxuate as
> described?
>
> When adding less then a gallon of coolant, can I use water only? I had
> the water pump changed last winter, and I don't know what type of
> coolant was used. Can I just match colors?
>
> Thanks for the help.
>
> CTM
>

Re: 91 YJ Heater problem
 

your core could be clogged. unhook both hoses going to the heater core, at
the engine side, and stick a garden hose on the side where the coolent flows
back to the engine. Turn on the hose and watch your core cough up some
horrible junk! Your all set now...
Nick

<testert555@gmail.com> wrote in message
news:1136493497.626621.47840@g44g2000cwa.googlegro ups.com...
> 91 YJ 4.0 (125k miles, no AC)
>
> While driving home from work yesterday I noticed the heater was blowing
> cold air only. This may have started several days ago but I really
> didn't notice. I watched the temp and it remained consistant (210 +-3
> degrees).
>
> This morning on the way to work I was ultra paranoid about the temp. I
> noticed at highway speed it was normal, but at highway stop lights (2
> min) it would creep up (+10 degrees). Once I got moving again the temp
> would go back to normal.
>
> At the office I checked the coolant level and found it to be low (I
> could see it at the bottom of the resv). At luch I went out to get
> some coolant and magically the heater was working fine. After driving
> the Jeep to normal operating temp, I idled for 20 min without
> experiencing a large jump in the temperature.
>
> Would anything other then a block in the heater core cause the lose of
> heat? Would a blocked heater core cause the temp to fluxuate as
> described?
>
> When adding less then a gallon of coolant, can I use water only? I had
> the water pump changed last winter, and I don't know what type of
> coolant was used. Can I just match colors?
>
> Thanks for the help.
>
> CTM
>