yj over heating at hwy speed

[budman]

Hi,
I have a 89 yj with 4.2,nutter bypass,webber carb.The problem is it overheats at highway speeds only,I can start it up and let it idle for hours and it stays at 180* no problem,drive around town no problem,but get it going 50 mph plus and the temp just starts to slowly rise in the summer time but is not as bad in the winter.It has a new 3 row radiator,water pump and thermistat.I don't have much air comming out of the exaust so am thinking the catalytic converter is stoped up?Any imput would be great I am my witts end with this problem,THANKS George:???:

 

[Saddle Tramp]

Thermostat, Head Gasket, Got Coolant?

 

[SteelHeadz]

Pressure test the system with a pressure tester and see if the pressure drops. If it does, look for external and internal leaks. 180* is a little cold for me. It should cycle around 195*- 205* the most at idle when the thermostat opens and closes. A partially sticking thermostat can also cause this issue only when the vehicle is driven at higher speeds. If the catalytic converter is plugged up, you will have issues with the engine performance when accelerating and progressively loose power as the engine gets hotter. In thoery, if you have an existing internal leak on your cooling system such as a bad head gasket or a crack in the head, the plugged up catalytic converter should push more exaust gasses into your radiator as it builds up pressure.

 

[jfrabat]

Pressure test the system with a pressure tester and see if the pressure drops. If it does, look for external and internal leaks. 180* is a little cold for me. It should cycle around 195*- 205* the most at idle when the thermostat opens and closes. A partially sticking thermostat can also cause this issue only when the vehicle is driven at higher speeds. If the catalytic converter is plugged up, you will have issues with the engine performance when accelerating and progressively loose power as the engine gets hotter. In thoery, if you have an existing internal leak on your cooling system such as a bad head gasket or a crack in the head, the plugged up catalytic converter should push more exaust gasses into your radiator as it builds up pressure.

a plugged cat will cause some other issues besides overheating; I agree everything else, though. And like saddle mentioned, check the coolant level (this has happened to me before). Could also be a clogged up radiator...

 

[budman]

Hello and thanks for the replies,the radiator thermastat and water pump were replaced in January and I did a presure test then and it held 15 pounds for thirty minutes so I called it good.I have had it for about a year and to me it has never had any power and has had the over heat problem since day one,but I only have my old 49 cj3a to compare it to.It was in a bad state of tune when I got it,carb adjust,timing,vac lines bad and off so thought that might have messed up the cat converter.Well I ordered a new high flow cat and exaust system today from quadratech so will get put that on and see what happens,told wife I needed it any way HE HE.
Will post results later in the week...George

:shades:

 

[jfrabat]

told wife I needed it any way HE HE.
:shades:

Well, in THAT case, I think you should probably replace:

Headers, cat, and cat back
TB and spacer bored to 62mm
Performance Distributors's ignition with Screaming Deamon
Performance Cam and tappets
high flow water pump
BRX radiator hoses
Aluminum radiator
Mean Grean alternator
OBA
Lockers
D60 axles
NV4500 transmission
Atlas TC
a bunch of skidplates, bumpers, roof rack, winch, rock sliders, etc
Electronics (new stereo, CB, GOS, etc.)
Lighting upgrades
New tires and wheels with beadlocks

ALL of these things DIRECTLY affect engine temp, so you should tell your wife they need to be replace/added IMMEDIATLY! :lol:

 

[Utah_jeepster]

jfrabat, do you have a moment to call my wife too?

 

[budman]

Well I passed the list on to the wife but all I got back was " NO" but I sure do like the way you guys think. George

 

[jfrabat]

jfrabat, do you have a moment to call my wife too?

I have a hard time convincing mine of buying stuff!!! LOL.. Although since I got the offer to move to Costa Rica, I have managed to convince her (dont know how yet!) of letting me buy the front bumper, the winch, and 5 new BFG MT KM2 33" tires (and one wheel) all at once (provided we accept the offer)...

 

[firedude]

If it still has a clutch fan make sure it is working.

 

[jfrabat]

If it still has a clutch fan make sure it is working.

This would not matter at highway speed; in my case, at highway speeds, my e-fan stays off, and my jeep runs cool...

 

[T-rav]

Not trying to put you down but did you make sure that you didn't put the new thermostat in backwards. ?? Just a thought.

 

[firedude]

This would not matter at highway speed; in my case, at highway speeds, my e-fan stays off, and my jeep runs cool...

I have seen problems at highway speeds with a bad clutch fan. Also make sure the lower rad hose is not collapsing. Does it have a spring?