Overheat

Death-Mobile · 01-28-2006, 07:17 PM

My brother just got a 94 XJ with a bad water pump. I replaced the pump for him and put a new thermostat in since the housing had a bad leaky gasket. He went and refilled the system. Now he is saying that at idle the jeep is running hot (225-230) but when he starts driving it goes down to 210. What do you think could cause this? I was thinking he may not have bled it correctly or the thermostat is bad, just seeing if anyone else had similar problems with the cooling system.

Blue XJ · 01-29-2006, 03:52 PM

could be air in the system still

Shenck · 01-29-2006, 08:07 PM

Classic case for the mech fan clutch. Its like $40 at autozone. I had the same problem and a new fan clutch solved it.

The Mangler · 01-29-2006, 08:41 PM

I have another question about overheating.

My friend's Jeep overheats at highway speed but cools down if he slows down to around 50. Any of you ever heard of this before?

I don't think fans would be an issue, because at highway speed you shouldn't need them. We can't figure out why it only overheats at 70mph or more.

Shenck · 01-29-2006, 10:34 PM

[quote=The Mangler]I have another question about overheating.

My friend's Jeep overheats at highway speed but cools down if he slows down to around 50. Any of you ever heard of this before?

My only "guess" would be flow. Your friend seems to be getting enough flow of coolant to work at lower speeds but at higher speeds the flow isn't good enough. Could be restriction in the coolant system, water pump on it's way out, or just a "somewhat" bad radiator.

mrbill · 01-29-2006, 11:06 PM

Quote:

Originally Posted by The Mangler

I have another question about overheating.

My friend's Jeep overheats at highway speed but cools down if he slows down to around 50. Any of you ever heard of this before?

I don't think fans would be an issue, because at highway speed you shouldn't need them. We can't figure out why it only overheats at 70mph or more.

My guess would be that the lower radiator hose is collapsing (there should be a springin it). At speed if there is no spring or it has weakend, the hose will collapse due to the increased suction caused by the coolant rushing through the house. Good Luck!

The Mangler · 01-29-2006, 11:10 PM

Quote:

Originally Posted by mrbill

My guess would be that the lower radiator hose is collapsing (there should be a springin it). At speed if there is no spring or it has weakend, the hose will collapse due to the increased suction caused by the coolant rushing through the house. Good Luck!

That is definatly worth checking out. I never would have thought of that. Thanks.

AZ Jeff · 01-30-2006, 12:13 PM

Quote:

Originally Posted by mrbill

My guess would be that the lower radiator hose is collapsing (there should be a springin it). At speed if there is no spring or it has weakend, the hose will collapse due to the increased suction caused by the coolant rushing through the house. Good Luck!

Or a bad rad that is plugged enough that the heat from higher speed running cannot be transferred out thru the fins.

The Mangler · 01-30-2006, 06:15 PM

...Well, it's not the lower hose...

Quote:

Originally Posted by AZ Jeff

Or a bad rad that is plugged enough that the heat from higher speed running cannot be transferred out thru the fins.

Wouldn't that affect low speed driving too though?

91_Cherokee · 01-31-2006, 06:59 AM

I'm tracking down an over-heating problem in my '91 now.

Mine heasts like that...Unless I run th eclimate controls on Def, or AC....So it seems the electric fan isn;t coming on, unless the settings are on those.

In other words, double check the 12v fan, I think its supposed to come on at 220, no matter what.

JaMMin2525 · 01-31-2006, 05:34 PM

i have traced my occational overheating problems to the fan clutch. But when i go to autozone to buy one they ask if mine is mechanical or electrical. I have an 89 4.0 aw4. which one is it??

Thanks!

-Jamin

anony91xj · 01-31-2006, 06:09 PM

Quote:

Originally Posted by The Mangler

I have another question about overheating.

My friend's Jeep overheats at highway speed but cools down if he slows down to around 50. Any of you ever heard of this before?

I don't think fans would be an issue, because at highway speed you shouldn't need them. We can't figure out why it only overheats at 70mph or more.

Flow problem. Could be a bad water pump, could be a plugged radiator, could be just that the coolant level is low, could be that the thermostat isn't opening all the way....

**Blake** · 01-31-2006, 06:18 PM

Quote:

Originally Posted by JaMMin2525

i have traced my occational overheating problems to the fan clutch. But when i go to autozone to buy one they ask if mine is mechanical or electrical. I have an 89 4.0 aw4. which one is it??

Thanks!

-Jamin

Mechanical.

YJinSD · 01-31-2006, 06:57 PM

Quote:

Originally Posted by The Mangler

I have another question about overheating.

My friend's Jeep overheats at highway speed but cools down if he slows down to around 50. Any of you ever heard of this before?

I don't think fans would be an issue, because at highway speed you shouldn't need them. We can't figure out why it only overheats at 70mph or more.

Mine was doing the same thing, and it was the radiator. That didn't bring it back completely, but it is below redline, I'm thinking a regear will put it right. It does rev pretty hard at 70.

AZ Jeff · 01-31-2006, 09:21 PM

Quote:

Originally Posted by The Mangler

...Well, it's not the lower hose...

Wouldn't that affect low speed driving too though?

Engine generates more heat at higher speeds, thus needing to dump more heat thru the rad.

01-31-2006, 06:59 AM	#10
91_Cherokee Registered User Join Date: Jan 2006 Location: South Central Virginia Posts: 27 Profile Gallery Classifieds My Jeeps	I'm tracking down an over-heating problem in my '91 now. Mine heasts like that...Unless I run th eclimate controls on Def, or AC....So it seems the electric fan isn;t coming on, unless the settings are on those. In other words, double check the 12v fan, I think its supposed to come on at 220, no matter what. __________________ [COLOR="blue"]-Billy[/COLOR] [SIZE="1"]1991 Cheroke Laredo, 4.0 HO Auto, Black...Stock! ________ \|l_\|__\___\,___ l--___--_[olllllllo] ()_)' ' ''()_)---)_) [/SIZE]

01-29-2006, 08:41 PM	#4
The Mangler Registered User Join Date: Jan 2006 Location: Texas Posts: 75 Profile Gallery Classifieds My Jeeps	I have another question about overheating. My friend's Jeep overheats at highway speed but cools down if he slows down to around 50. Any of you ever heard of this before? I don't think fans would be an issue, because at highway speed you shouldn't need them. We can't figure out why it only overheats at 70mph or more.