I posted this in General chat forum but I meant to put it here.

Hey all,

Just drove my new XJ home, about an hour drive. I kept a close eye on the engine temp, after reading all of the threads about overheating.

It stayed perfectly in the middle, right where I expected it (all highway driving), but when I opened the hood to snap some shots, I nearly burnt my hand!!!

It was way hotter than any engine bay I've seen. Its pretty hot here today, but I dont think the pop rod should burn me...

Could my gauge be reading way off?

 

My under-hood temps get very hot also. People often comment on how hot the hood gets, but it's normal as far as I'm concerned.

Nothing a couple hood vents won't solve.

 

OK thanks, good to know.

I would like to keep it as clean and stock looking as possible, so as long as its just me getting burnt, and not my truck, I am happy.

 

Hood vents will not "solve" underhood heat. I doubt they would even make 1-2% difference. Not enough to tell.

You touch something under there, especially metal, it's going to probably be hotter than sticking your hand in boiling water.

 

Don't worry so much about the engine bay temperature (which is always hot on a summer day) , but the engine coolant temperature. And the 4.0 like most engines is designed to run pretty warm.

If you are in the middle of the coolant temperature gauge, you should be fine. If you really want to know, point a laser thermometer directly at the thermostat housing of a hot engine. 195-205 is pretty typical.

With a "new to you" XJ, you should be creating a to-do list. Tune up parts, cooling system maintenance including hoses, fresh oil, transmission fluid, transfer case fluid, differential fluid. You get the picture. Unless you have believable records to show what has been done, there are very few "new to you" vehicles that don't need some basic maintenance work.

But the good thing? You have a 99, which arguably is one of the best years for the XJ! Ask me how I know? Enjoy your XJ!

 

I cut some hood vents in and my xj literally runs 15-20 degrees cooler with the ac on in the heat. It does make a difference. My xj used to run like 240 with the air on in traffic. Since I put hood vents in, it hasn't got above 220

 

^ Excellent advise!

 

They do help a lot. Look at the hood of a police cruiser, most have vents on them. Without any ventilation the air from the cooling fan just packs into the engine bay with no where to go. Hood vents let that hot air escape and more cooling air to flow in.

 

Here's my theory on XJ engine heat. Guy buys his first XJ. It's old so he goes to forums and starts reading about all the problems. His stress level goes up and he decides to learn how to work on old cars.

He's never had to get his hands dirty before, 'cause he and the lady have a nice Subaru that never breaks down, and his wife takes it to the dealer if needed.

Guy never had to open a hood on a hot subaru motor. But he opens that hood on his XJ, and WOW- it's dang hot. Holy cow- this thing is going to explode and melt. Hurry- get on internet and read about XJ heat.

Search results: vents are the magic solution. It's a proven fact- cause you can read it on the internet. Ignore that they also replaced the entire cooling system. The XJ runs so cool now it seems to make ice as it hauls down the freeway.

Please don't get offended if you have proven the hood louvers work. But some of us old timers are going to get hurt when we fall off our chairs laughing every time we read about burning your hand on the XJ motor. This post is for us.

 

If XJs always overheated without hood vents, then AMC or Chrysler would have put them in at assembly.

XJs have been and still are used everywhere and anywhere in the world in all climates.

If you have an XJ that runs at 240*, you've got a bigger problem than lack of hood vents.

No police car in my area has hood vents, and it gets to be 114* degrees here from time to time. We can have up to 40+ days of temps near or above 100* in the summer.

Since the fan is drawing in air, the air in the engine compartment has to go somewhere. It goes under the car and out into the atmosphere. Simple, and unavoidable, physics. It cannot "pack in there", as air is a fluid and flows from higher to lower pressure and transfers heat from higher to lower temperature.

 

^Yea, The airflow from fans travels down the transmission tunnel, giving needed flow to oilpan/exhaust, transmission etc.
The 500 degree exhaust pipe sits 1/2" from the oil pan, redirect too much of the airflow and the oil temperature may spike.

Struts that lift the hood hydraulically will eliminate 'hot hands' when opening hood.

 

The only way to reduce heat is to exhaust it with airflow.

That's it, no other magic is required.

Dual Efans.

 

Noisy.

 

Huh.. Never thought if it like that but it makes complete sense. The exception I could see is at a stand still when airflow is reduced having "selectable" hood vents would be nice.

As people have mentioned, treating heat with a bandaid is not the best approach. Better to try and fix it by replacing old/faulty/worn out cooling components first.

 

Yeah I definitely dont feel the need to cut holes, and I for sure wasnt panicked about the heat.

I have worked on all of my own cars, have owned many different engines, from 4's to 8's, rotary and boxer, none of the engine bays ever got this hot so I just wanted to check it out with you guys. Not sure if your reply was directed at me, but seems you took a bit of a jump there judging me...

Anyway, like I said, if its normal for this engine bay to be that hot, then I am moving on and worrying about other maintenance issues. Cooling system was just one of those check-marks on the list.

Thanks again.