Hello guys, so about two weeks ago I noticed the car said my engine coolant was low, refilled it & though nothing of it (had been a while), this past Saturday morning on the way to dropping my mother to work (her car) I noticed the light came back which raised some concern. Refilled once again & within minutes of driving the light came back on but the car still had not overheated.

Refilled it once again on Sunday & noticed a little bit of dripping, took it for a short drive & the light remained, but when I turned the car off the radiator fan continued to run. Monday brought it to a local mechanic I was referred to & on the way there it started to overheat for the 1st time (never passing the 1st hash mark after the middle). Mechanic called back & said it was the radiator & a $1200 fix. Does this sound like a fair estimate?

 

A few things;

1. The temperature gauge will not tell you the car is overheating until it's well & truly cooked. So the car has probably been running hot & you just never saw it.

2. Where is the leak coming from? Is it just coolant forcing it's way out due to pressure or an actual leak?

3. The thermostat is the first thing to remove, test and replace, then i'd be looking at radiator & or water pump. Take out the thermostat & drop it into a glass of boiled water, I can guarantee you it will stay closed.

 

I believe the OP is saying the car is overheating because its leaking out all its coolant, not because of a thermostat problem. OP then took it to a mechanic who very likely (I would hope, anyways) pressure tested the cooling system and determined that the radiator was leaking. Seems pretty logical to me. Price is on the high end, but if you are paying someone to fix it, then full retail + labor would probably be close to that amount.

 

It was not stated that the radiator was leaking. Just that the car was running hot and there is coolant loss.

A leaking radiator doesn't make a car overheat unless the coolant has completely leaked out and there's nothing left circulating in the system. My S-Type has a leak & looses a whole reservoir every tank of fuel. Doesn't overheat though...

In the OP's case it could be a blocked up radiator that's making the car run hot, but raditators tend to last a lot longer than thermostats do...

2005 model is pushing 9 years old, you can bet it's still got it's original thermostat in it.

Where is the leak? Could be coming out of anywhere...

Why is it overheating? First thing to check is the thermostat...

 

Basically that's exactly what happened, mechanic said he would pressure test it & that was his finding.

 

If you believe him then fair enough.

I am still of the opinion that a leak in a radiator that doesn't lose "much" coolant will not cause overheating, if it loses the lot then yeah ok fair enough.

$1200 supplied & fitted is on the high side but not outrageous.

But for your $1200 you'd better be getting a new thermostat as well...

EDIT

I have had to change the thermostats in my XJR and my S-Type, they do not last forever!

 

If you are mechanically inclined, change it all yourself. Do the upper, lower and other hoses too that are in front of the engine. You'll have to disconnect the AC system from the front of the radiator.


It is not a bad job, but I have the experience, too.

 

Is the radiator & all the other components something that I can easily find online, if so what sites are recommended?

 

Very easy to find. Also, you can find it through Rock Auto:


RockAuto Parts Catalog


I'm assuming that you have the 3.0 V6 but they have all of them available.

 

From the scenario you described, I would want the tech to really scrutinize the coolant outlet housing, the big black pipe assembly that contains the thermostat and the temp sensor. They can fracture and start a small leak the runs back on the engine and boils off before it leaks to the ground. Secondly, it can also fracture internally so coolant just recirculates in the engine and never gets put through the radiator. Sort of mimics a restricted radiator. That can explain the eventual overheat even though you didn't have a total loss of coolant.

This is also assuming you have the 4.2L V8; you don't mention V6 or V8. Your description pretty much pegs a V8.

Good luck!