XJ6 & XJ12 Series I, II & III 1968-1992

Too hot

 
  #1  
Old 07-28-2016, 03:35 PM
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Default Too hot

Temp today was way high, phone said it was overheating when i left it in car to run into the grocery store!! Car was running at about 105, although in the so called safe green section its a bit too hot for my liking, 30 secs witha garden hose through grill and sitting just below 90 again! So... does it mean its just really hot out, or do.i have a problem? I would assume partial blockage of radiator because hose brought temp down really quickly. But my logic has.been wrong before.
Coolant is nice and green, almost 2 years old, maybe 2000 miles on it.
What say you???

Edit. E fan is working fine too, didnt make a difference with ac on or off(well it made a differenceinside.the car. Lol )
 

Last edited by Darrenmb; 07-28-2016 at 03:37 PM.
  #2  
Old 07-28-2016, 05:26 PM
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Originally Posted by Darrenmb View Post
Temp today was way high, phone said it was overheating when i left it in car to run into the grocery store!! Car was running at about 105, although in the so called safe green section its a bit too hot for my liking, 30 secs witha garden hose through grill and sitting just below 90 again! So... does it mean its just really hot out, or do.i have a problem? I would assume partial blockage of radiator because hose brought temp down really quickly. But my logic has.been wrong before.
Coolant is nice and green, almost 2 years old, maybe 2000 miles on it.
What say you???

Edit. E fan is working fine too, didnt make a difference with ac on or off(well it made a differenceinside.the car. Lol )
Check all the basics...fluid level and clutch fan operation. If they check out ok remove and flush the radiator. Silt can build up at the bottom and restrict flow. Also will provide an opportunity to remove debris that can restrict air flow.
 
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Old 07-28-2016, 07:02 PM
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If its an old radiator, I would just buy a new replacement. Good insurance for the life of the engine when you get hot days, trapped in traffic,.. needle rising past 110,..ittybitty aux fan spinning its heart out ...and the hoses ,..so many of them, all potential for leaks under pressure from overheating. I say all this because I have had the problem of all the trash (scale and God know what else) circulates through the cooling system. coming to rest at the bottom of the radiator,,,restricting actual cooling area. Radiators and hoses are cheaper than rebuilding a dead engine / replacing head gasket. Cooling is not so good with just a stock fan.
 
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Old 07-28-2016, 07:10 PM
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If its an old radiator, I would just buy a new replacement. Good insurance for the life of the engine when you get hot days, trapped in traffic,.. needle rising past 110,..ittybitty aux fan spinning its heart out ...and the hoses ,..so many of them, all potential for leaks under pressure from overheating. I say all this because I have had the problem of all the trash (scale and God know what else) circulates through the cooling system. coming to rest at the bottom of the radiator,,,restricting actual cooling area. Radiators and hoses are cheaper than rebuilding a dead engine / replacing head gasket. Cooling is not so good with just a stock fan.
 
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Old 07-29-2016, 05:05 AM
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I agree with the above.

The fan hub/clutch is #1 on my list, followed real close by the radiator silting yp.

Many of the XJ series were not fond of idling with the a/c on for too long..

The hose cooling it down so quickly has me on the fan clutch like a rat up a rafter.
 
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Old 07-29-2016, 06:39 AM
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im more apt to blame radiator than fan clutch as it was running hot at 70 mph on freeway and in town in traffic, but im not going to ignore it as anything is possible!
it actually dropped a little in town! back to around 100, still too high for my liking! i don't like to be over the 90 mark!!! not that it ever over heated, just was hotter than i am happy with!!!
There is nothing between rad and condenser as i had radiator out while doing head 2 years ago, and like i said in original post, only has about 2k since then.

Reckon im gonna buy a new rad and fan clutch as insurance..
anyone know of a good replacement better than stock rad??? part number and or vendor would be great!!
Thanks
Darren
 
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Old 07-29-2016, 09:26 AM
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Check out Andrew Weinberg's site, Jaguar-specialties. His comments are for lumped cars, but, a lot transfers. Cheap ,but light and effective.
alloy with plastic tanks. Camaro or Mustang sourced.


And, consider E fans.


Or, if your tanks are solid, a boil out or quality recore will get you a lot more miles.


My lump purposely runs at just over 90C on a big four row brass side flow and dual Efans managed by the PCM.


Don't let that misleading green on the guage lead you astray. Why green in a danger zone????


I went to market yesterday, early. Already in the 90's F ambient!!!
Jag held constant at 90C. No fans while moving. Only when I slowed
to enter the drive did one come on. Perfect management. I could use an optional lower temp T'stat. But, the LT1 is designed to run at up scale numbers. I figure the GM engineers know better than I. Although a lower t stat will pick up some added power.The LT1 as installed isn't lacking there.


CAVEAT: Idling isn't good. With AC on, worse. lectured daughter on that. Nursing her high mileage Passat along. Move it, or get out and go indoors........ Still got it... That Dad thing...


Carl
 
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Old 07-29-2016, 11:40 AM
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I live in Phoenix and have a lot of experience with running hot. as said before, If hot while moving through the air( driving) Radiator. if only hot while standing; not enough air. Fan(s).
If you have fan problems, make sure you have a good shroud. Also, today's thinking; fans in front of the rad are not helping, but are restricting.


I run a 4 core old brass rad with a Flex fan. It works ok but builds heat with multiple grocery stops.


On my current refurbishment of the whole car I'm going to new, better aluminum rad and thermostat controlled inside fans.


hope some of this helps you.


geneo
 
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  #9  
Old 07-29-2016, 07:32 PM
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Originally Posted by Darrenmb View Post
Temp today was way high,

Like 90-100F?


phone said it was overheating when i left it in car to run into the grocery store!!

You left in running how long? Were you in the store 5 five minutes or 20 minutes?

Car was running at about 105, although in the so called safe green section its a bit too hot for my liking, 30 secs witha garden hose through grill and sitting just below 90 again! So... does it mean its just really hot out, or do.i have a problem?

Maybe both.

You probably have a problem but it depends on the circumstances.

I wouldn't be a bit surprised that temp would *eventually* increase if the car was left idling in high ambient temps. But, if the needle starts moving up immediately upon being stopped .... that isn't right.

IME....On their very best day these Jags (and many others) do not enough cooling ability to hold thermo-rating temps under all conditions, all the time. The temp will increase. Some view *any* increase of thermo-rating as overheating, others do not. I don't, FWIW.

But I'd be uncomfortable at 110C as well....especially if it got that high very quickly.

On the bright side there is nothing exotic about the 4.2 cooling system. It's plain as mud. A new or professionally cleaned radiator and new fan clutch will probably do wonders to keep thing at a more comfortable level. No promise that it'll hold 90C temp 24/7/365, though.

Cheers
DD

PS- some have had great results with alum radiators from late model Mustangs. I'm sure there is some archived info
 
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Old 07-30-2016, 07:47 AM
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outside temp was 97 with a feels like of 105.
when i ran into grocery store car was not running, and phone was left in closed car, in store maybe ten mins top, was so hot out that the phone itself was overheating, and had shut off half its apps to try to cool down.

car temp was no different running at 70 mph or sitting in traffic once it reached 105 (which happened at 70 mph after about an hour at that speed) it never came down! (until hose was run through grill when i got home!) did not matter if ac was on or off.

I think that covers it.
 
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Old 07-30-2016, 09:32 AM
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Originally Posted by Darrenmb View Post
outside temp was 97 with a feels like of 105.
car temp was no different running at 70 mph or sitting in traffic once it reached 105 (which happened at 70 mph after about an hour at that speed) it never came down!

I think it should run cooler under those circumstances.

Radiator (new or professionally cleaned) and fan clutch should do the trick

Cheers
DD
 
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Old 08-01-2016, 09:37 PM
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I don't have numbers on my temp gauge. Just C normal H.

I have no clue what temp is what letter.

Mine is definitely running hotter than in the Spring.
 
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Old 08-01-2016, 10:02 PM
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Originally Posted by audibabba View Post
I don't have numbers on my temp gauge. Just C normal H.

I have no clue what temp is what letter.

Mine is definitely running hotter than in the Spring.

I find using an infrared temperature gun a must when checking engine temperatures.......very cheap on eBay.
 
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Old 08-01-2016, 10:39 PM
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I don't know if Jags heat differently, but an IR thermometer reads 213F on the thermostat housing of my Chevy 350 when the needle is on O of Normal with no apparent ill effects to operation. The back of the head reads 206F.
(';')
 
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Old 08-02-2016, 09:42 PM
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Thanks. Numbers are what I needed to know. I will have to check when it is really hot to make sure it is not too hot. I would think over 230F might be considered too hot. I will try to check this weekend.
 
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Old 08-09-2016, 12:02 PM
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Ok. So, on my gauge, the l in normal is approximately 215F on the thermostat housing with an emissivity of 0.9. After I shut it down, the temperature gauge went to halfway between the l in normal and the H. This read 230F at the housing.


What emissivity do you use for the thermostat housing?
 
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Old 08-09-2016, 02:37 PM
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Originally Posted by audibabba View Post
Ok. So, on my gauge, the l in normal is approximately 215F on the thermostat housing with an emissivity of 0.9. After I shut it down, the temperature gauge went to halfway between the l in normal and the H. This read 230F at the housing.


What emissivity do you use for the thermostat housing?
I've never heard of emissivity before, had to look it up!

When I measure my temp I don't worry about that. If it was my car, I wouldn't worry about a temp of 215F. 230F I would worry about if it was running at the time.

An engine always registers hotter after shut down. Water is no longer circulating through the radiator so the hot metal just keeps heating up the stagnant water.

I heard an XK-120 once that sounded like a percolator for an hour after it was shut down. No one had an IR thermometer at the time so we don't know the temp.
(';')
 
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Old 08-10-2016, 02:28 AM
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We should remember that water boils at 212F. I think that is a sea
level value. Lower at higher elevations. IC engines have operated at
this temperature safely from the beginning.


Pressure sealed cooling systems, at about 15 psi raises the boiling point. Glycol solutions boil at a lower temperature than plain water.


Cast iron engines do better than alloy engines in an "over heat"
environment. Alloy heads on cast iron blocks are even less permissive.


Allowing an engine to idle in hot temperatures is not a good practice,
The best fans don't approach the CFM of a moving car.


Note: When idling is needed in a repair shop, most place a fan in front of the car to increase the CFM. Customers don't understand why the head gasket blew in the repair shop!!!


My car is in my drive on ramps. Oil and filter change done. Swap
of inboard lamps for fresh ones raising far more fuss than anticipated.
Typical of my endeavours....


Carl
 
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Old 08-10-2016, 01:18 PM
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I have never seen the temperature halfway between the l and the H while it is running.


The highest I have seen is the needle next to the l or about 220F and that was on a 98F day at 80 mph. It creeps up and stops. If it ever keeps going, I will stop.


I ask about the emissivity, because that changes the temperature reading on your IR gun based on the setting. For smooth darker objects it should be closer to 1, but shinier or rough objects should be less.
 
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