Ok guys here's the story I'm gonna try and keep the long story short and as detailed as possible. Please let me know if you need any more info tell diag this headache of mine, it's a 2000 S type with 112k, I just recently had a "running hot" issue never over heating just made a hair over the half way mark. I took it on a longer drive than normal and it went up to about 3/4 and than back down to half way as I kept driving to my destination. Just today it sky rocketed to the red zone. So I decided I had a bad thermostat, changed that and followed the bleed procedure I found online. Car still over heats when I drive it. But it's fine at idle. At first I thought air in the system but I've bled and bled and Ed for hours today. Upper rad hose is HOT lower hose after thermostat is still warm to the touch. Sometimes cold

So we kept bleeding, finding more and more small spurts of air. the front bleeder seems to spin but will not pop up to release fluid and the rear(by the coolant tank) is where we have been doing the bleeding.

No odd check engine codes just my normal Cat that's been on for a week untill my replacements arrive.

Temp gauge seems to e a little jumpy and fans kick on and off but motor dont seem like it wants to over heat while I'm drive above half way. I can literally have it idle for an hour or two and half the gauge a hair under the halfway mark (noon) than take it on a 10 minute ride, heat off and it instantly goes up to 3/4 to 4/4 within 3 minutes. Turn the heat on and it drops back to half way.

I've begun to think it was a bad temp sensor because of how seperatic the gauge is. It will go from HOT (almost in the red zone) to me shutting the car off for 2 minutes and the gauge drops to half way mark instantly. (How can the car cool off that fast?) also I have hot air in cabin so can't be heater core. Air is burn your hand hot

I'm stumped. I called the local auto store and bought a 30.00 "coolant temp sensor" or so I thought. Than I read a bit on how 3.0s don't have a so called temp sensor they use the long engine temp sensor on the valve cover of the driver side. (Can anyone confirm this?)

I found that the sensor I bought was actually one of the two behind the AC compressor on the engine block. One was a 2 pin connector with a grey cap (oil temp?) although my temp sensor I bought fit in there and was exact same sensor it was labled coolant temp? Unless when I unscrew that sensor with grey top coolant is suppose to come out and not oil?
Anyway replaced that sensor and can't figure out what the 2nd sensor is down there? Knock sensor? One wire going to it with a black cap. Kinda looks like the same style as the sensor I changed.

For thoes of you who don't want to read the long version...

I'm out of ideas. No check engine light, heat off, car runs real hot, heat on, car still runs above halfway mark. After car is above 3/4 if I park and not shut off it floats down to halfway within 1-2 minutes at idle.
I've bled 1000 times but can't get center bleeder to pop out of place it just spins. Thermostat is changed is so is the 2 pin connector sensor behind the AC compressor. Fans kick on and off as they should an I have hot hot air inside the car

Any input would be greatly appreciated as I don't want to drive car over halfway mark because I've seen Lincoln LSs warp heads in a matter or minutes of driving hot

Someone help! More bleeding?? Bad water pump? Could my instrument panel be messed up and my gauge is funkin out. Is there a Real coolant temp sensor I'm missing?

Ahhhhhhh!!!

 

Ok, 1st of all the temperature gauge in jags is not a true temperature gauge, what I mean by that is focus groups in USA said people felt uneasy about a temperature gauge that moved too much so jag designed it to stay in the middle through massive temperature variations, if the needle moves from the middle it's overheating, badly.

Bare in mind these cars have aluminium heads and warp easily if overheated.

You don't say what size engine but these cars are notoriously difficult to bleed, especially the 4l v8, I've seen some take a few weeks even.

Another possibility is faulty water pump, (do they have plastic fins that break? Someone will know)

The new thermostat might even be faulty (I've had that 2 over the years)

Until you ger a few more suggestions I'd keep bleeding, get it up to temp, if possible park on a slope, bleed point high as I have heard this can help.

*edit* just seen you have a 3l v6

 

They do have fins that can break off.

Which engine?

 

What is the problem with your cats? Excessive exhaust backpressure -- A clogged catalytic converter will restrict the flow of exhaust and cause heat to back up in the engine.

 

I'm assuming he has a 3.0 since he mentions it in post.

This may sound trivial but it happened to me twice on my Corvette. Have you checked to make sure there is nothing blocking the radiator? On two occasions, once a plastic bag the second time it was paper off the road blew in and partially covered the front of the radiator. Same exact symptoms you have. The second time it happened to me I knew what it was. I removed the debri and all was good.

 

Hey guys just an update I tore the coolig system apart to find out my engine bleeder had broken and plastic bits were all in the cooling system. Flushed everything out and replaced the waterpump because I was already halfway there and bled the system once as was good to go! I managed to thread the broken bleeder screw in tight enough so it didn't leak air into the system or out untill my upper hose comes in the mail. All is good to go. Waterpump seemed fine and after a good flush everything worked well.

 

Good fix and thanks for posting back!!

We don't get much feed back and in the end we are all just guessing with limited information.
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Dealing with the same issue. Problem is that I can easily locate the heater bleed hose, but can't locate the engine bleed screw. Does someone have a diagram or very clear description as to where I can find it? I'm working on a 2000 S-type 4.0. Thanks.

 

the bleed hose is tucked in next to the brake master cylinder. Use a large flat blade screwdriver to loosen the plastic bleed screw and only open enough to let air/coolant to drop out... I can't stress enough to not over tighten the bleed screw.

 

Thanks for the information. I was under the impression that there are two bleed screws, one for the heater and one for the engine itself. So I've located the one between the master cylinder and the coolant reservoir tank, but I thought that one was specifically for the heater. Where's the other one? Again, I have a 2000 S-type 4.0.

 

I also have a 2000 - S Type 4.0 and the bleeder I mentioned is the only one to purge all air from the entire system. Please read up on JTIS bleeding procedure.

 

"Than I read a bit on how 3.0s don't have a so called temp sensor they use the long engine temp sensor on the valve cover of the driver side. (Can anyone confirm this?) "


I have a 2002 S-type 3.0 with the long sensor - reaplaced it last week.


There is a Cylinder Head Temperature sensor in the driver's bank between the ignition coils (search JTIS for CHT). Very easy to get to and replace - just unplug and unsrew. It's the long brass sensor not the other shorter sensor. Finding the part is the confusing part - there are many names under which it is sold (cooling fan sensor etc). I bought mine from FCP Euro. I would take out your sensor first to make sure that you have the CHT long brass sensor.

 

OK. Thanks. Unfortunately, I thoroughly bled the coolant system and my engine continues to overheat. Had the water pump replaced a few weeks ago and it ran fine up until a few days ago. I changed the thermo and bled out air but the engine temp still pegs into the red. At least the car's getting heat now! I need to figure out where to go next with this.

 

Does your electric fan work? It should run 100% when the A/C is on.

Has the car had any maintenance? If not you might need to change the radiator or at least try a flush or two.

Also the top tank is known to get cracks and you may not be holding pressure.

Do you get a whoosh of air when you crack the radiator cap when the car is up to temperature?
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Thanks for the reply Tbird. I'll answer your questions in order.

1. Fan runs as it should.
2. Car gets maintained but it hasn't had a rad replacement, nor a flush lately so I'll flush first and see where that gets me
3. Had the coolant system pressure tested a few weeks ago, and I have no visible dripping of coolant in the areas you'd expect if the tank was leaking.
4. There is a whoosh of air when the tank lid is turned open.

When I bled the system, as the car reached operating temperature, I eventually got a good, solid, steady stream of hot coolant coming from the bleeder valve. There was def air that needed purged. Took a little less than 10 minutes to get a solid stream of coolant, but after I had it flowing solidly for about a minute, I stopped the bleeding process. Heat was cranking inside the car, temp gauge was at the halfway point so I was feeling pretty good. The car will idle all day like that, but as soon as you take it on the road and get the rpms up there, it doesn't take more than a mile and she's red lining. I'll check out the radiator, and I'm going to bleed the system again; this time for a longer cycle period to make entirely sure I've purged all of the air. I'm not even thinking head gasket at this point. I'm not even going to mention it! ;o)

 

A number of owners who have flushed their cooling systems have reported that it can take days for all of the air in the system to finally work its way out. So you may still have a few air pockets to contend with....

 

hii Guys I have also a overheating problem with my XKR 2001 Mostly the temp gauge stays in the center even in traffic jam ( i am living in Dubai ; temperature around 40 C is normal here ) and suddenly it peeks to the red zone but never reach it before dropping very fast again to the center . I replaced the thermostat , flushed the cooling system and replaced the cooling liquid . The problem its still there . What i dont understand ; i followed the filling procedure for the cooling liquid . i could only fill about 5L but normally should be 11L Am i right ? A second problem ; there are two fans on the radiator but only one is working . (I couldn't check if the second one was working when the gauge was nearly in the red zone ) . Should they always spin together ?

1/ 11L contenance but can fill only 5 L
2/ is there another way to bleed ?
3/ should these 2 fans spin together
4/ if they should spin together , why they dont ?

can anybody help me with these questions

 

Please re-post in the right forum.

 

sorry i am new here haha its a XKR 2001 convertible engine V8 4L supercharged
106 000 km

 

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