Slick761

If the coolant is flowing enough it will still cause suction if the pump were in the radiator no.... but that bottom hose is the weak spot so to speak. Has to flow enough for this situation to occur.

cptmohog

Aux fan is new and working properly, recent oil change, ambient temp around here is about 105 right now.

forgive my lack of knowlage here, but what is this spring in the lower radiator hose you speak of? I just bought new hoses from autozone, don't know if they have a spring?

A buddy brought up a good point last night that I hadn't thought of: I have one of those aftermarket "tomken" lazer cut grills. When I installed it, I still had the old gauge cluster with the idiot lights (before I realized I was running hot) He thinks the air flow might be restricted. Don't know if that would explain 225? I am going to put the OEM one back on tonight and see if that makes a differance.

To the guy that suggested exhaust: My manifold has a crack, and my muffler is squished (previous owner) I haven't got around to replacing those yet...could this be contributing to the problem?

Slick761

Originally there was a spring to help hold the lower hoses shape at rpm. Just take the grill off and run it. If there's a huge change there's your issue.

FL Denmark

X2 on the grill. Lack of air through the radiator will make it run hot.

The cracked header would not case extra heat. Neiter would the mufler, as it is to far back.
But the cracked header can cause our mpg to go done as the o2 sensor reads incorrect.
I would replace the header.

jeepkid03

Hows your fan clutch?

djb383

Why wouldn't the bottom hose collapse (but it doesn't) when the motor is started cold, since there's no coolant flowing thru the rad due to the t-stat being closed? The pump still turns/sucks when a cold motor is running, right?

We just did a radiator install on our XJ less than 4 weeks ago (no previous overheating issues and the new rad was the last part of our cooling system maintenance). On our XJ, there's no spring in the bottom hose, when the motor is reved (hot or cold, the bottom hose does not move, much less collapse.

On our 45 minute test run (after rad install), ambient was 106 (thank goodness for a/c), coolant temp peaked at 208 (ScanGauge) doing 0-30 mph in town and dropped to 194 at 70/75 mph hi-way.....no spring and 180 t-stat. YRMV.

Slick761

The less coolant pumping the less chances of it happening. At higher rpm with the thermostat open that small hose has trouble keeping up with the demand. Also when the hose is hot and soft it raises the chances. When your hose gets older it might start doing it. It's nice and solid new. Then again it might not :-)

djb383

All I'm saying is, I'm not buyng into the collapsing hose theory. Doesn't happen on our XJ, have never experienced it happening on any other vehicle I've owned. I have seen a bad rad cap collapse hoses when the motor cooled (motor off). Usually old hoses leak/burst.

Slick761

The fact is the.engineers that design cooling systems put springs.in. they didn't do it cause they thought it would be neat. Car companies are not about spending extra money without purpose. I'm not saying you have to have it but under some testing condition the factory had issues with the hose restricting flow. Otherwise they certainly would not have had to design a way to keep it from happening. You can pick these things up at the parts store for nothing. I like keeping things the way they were made. Just my thing.

djb383

Those engineers that gave the rad hose a spring, were probably the same engineers that gave the XJ an 11" tall radiator..........brilliant!LOL

Slick761

The cooling system isn't the best. When its on good condition though it does the job. You gotta figure with as lean as these things run they create A LOT of heat.

djb383

Yes, the XJ cooling system leaves a little to be desired (that dinky radiator).......that's why I've said, what seems to be a thousand times, every component of the cooling system must be in top notch condition. I get weary of reading posts that say "I'm overheating, I changed the rad cap, what else could it be?" LOL

Slick761

Lol. That and the cooler tstat and people hardworking their efans to the ignition. Putting band aids on problems to mask the bigger issue is a major pet peeve of mine.

djb383

Don't mean to peeve, but the 180 is staying in our XJ.

Slick761

You've already redone your system. You aren't masking a problem. That's personal preference. To each his own.