Hello all,


So today while I was driving I got a engine temp high and then a engine overheating on my dash... The fans are still coming on no coolant leak and no smoke or anything coming from the engine compartment... I wanna change the thermostat and its housing first what's you guys thoughts???

 

Any check engine light codes? It could be a seized water pump, but that would probably leak at least a little. The thermostat would make sense. I'd probably check that first too.

Govtslug

 

Thx I checked for a leak and there is not even a little and it only happens when it's extremely hot out like 90's or more since Saturday... I'm going to pick the part up from the dealer tomorrow and I'll post the install and results

 

I would read the codes in the OBDII port and then erase them. Let the car sit for 6-8 hours and then start it up and see if the lights/codes come on when the car is cold. it takes usually 3-5 minutes before you get engine temps up to 150* and that should not set any lights. If the lights come on when you start it then I would suspect a sensor or two being bad. If no lights/codes come on until lets say 8-10 minutes then all is OK but if the lights come back on after that time you have a problem. Do this before you start throwing money at the car.

 

Oh if you have a Torque pro BT OBDII setup you can read your temp.

 

Ok I'll try that but the the warning only comes on after I'm driving for an hour or so only if it's extremely hot outside... Will the OB2 read if there aren't any codes/lights on the dash besides the high temp warning?

 

The plastic thermostat housing (including the entire plastic pipe assembly) deteriorates at this age and mileage on the 4.2 engine. Thermostats can fail also at any time and sometimes stick intermittently. The housing/thermostat replacement is good preventative maintenance on this car, relatively inexpensive and probably will also solve the problem.

 

I would consider getting a BT OBDII reader and use a BT app to read temperature.
Now if you are driving for a while and the lights come on and you don't see or smell antifreeze and the fans are on something is wrong and you need to shut down and wait until it cools. You either have a choice to take it to a dealer or investing in something to read the engine temp. If you have a faulty thermostat you would get the overheat problem within the first 10-15 minutes of the engine running.

 

I've had this issue off and on as well, but I've caught it throwing a code for faulty ect once in a while. Haven't replaced yet, but I'm going to do both ect sensors, and thermostat housing and piping on my '10 this winter. I was told by the dealer there was an "upgrade" to this part anyway.

 

Thx that does sound about right and that's the problem it seems I'm having

 

Thermostat with age sometimes "stick". Usually, they stick closed, though some aftermarket thermostats advertise that they will, upon fault, stick open.

The quick and cheap way to determine if your thermostat is stuck closed is to check radiator temp by touching radiator with your hand. If it is cool, warm and you are able to touch it, and the car's coolant temp indicator is hot, then your thermostat is stuck closed.

A thermostat can also open only partially. You can also use a hand held infared (sic) thermometer to find hot/cold spots. They cost about $30 at Harbor Freight.

Changing out your thermostat is easy. Just let the motor cool, drain radiator and undo a few bolts. It is not rocket science.

The Jaguar thermostat is unique to Jaguar. The Jag thermostat is calibrated to open at 195F (as I recall). I have tried to find an interchange cooler thermostat with no luck. Has anyone found a cooler thermostat?

 

A cooler thermostat would not be desirable even if one was available.

 

I respectfully disagree with Mikey respecting cooler thermostat as not being desirable. I think that is just too broad a statement to make without documentation.

The Corvette community has offered/used/endorsed cooler thermostats for many years. In my opinion, the principle benefit of a hotter thermostat is emission reduction due to a hotter motor. My own experience in Minnesota winters with 160F thermostats was no material loss of cabin heat.

My information source is A. Graham Bell, a Brit who has written extensively about tuning English cars. I quote from his book "Four-Stroke Performance Tuning". In my opinion Bell is a great source. He also has a book "Forced Induction Performance Tuning", which may be of interest to XKR owners in particular. Both are available from Amazon and are great reads. Note, Bell does not remark about emission benefits from a hotter thermostat and fuel injected motors. Nevertheless, I think his remarks are still applicable to the modern Jaguar motor. Page 575:

"A high-temperature thermostat, which maintains the water temperature at 88-90C is usually fitted to production cars, but that is not the temperature for best power. The 88C thermostat is fine if you want good heater efficiency in winter, and the higher temperature partly compensates for the stock manifold and carburettor being unable to vaporise the fuel properly, but apart from that there is no reason for its use.

Some feel that high engine coolant temperature in the range of 90-100C is good for power. The theory is that anything lower just takes away heat energy, which we should be using to push the pistons down and produce more hp. To an extent this is true at low engine speeds and small throttle openings, but generally in a full-throttle, high-rpm dyno test an engine will make more power at coolant temperatures in the 70-80C range. Only dyno testing will confirm what is ideal for a particular engine, but in my experience I rarely see an engine that makes more power running higher than 84C or less than 68C. I have seen engines gain 2-3% hp when the temperature was dropped from 90C to 70C, conversely I have seen gains when temperature was pushed up from 65 to 80C."


Personally, my XK is mildly driven (I'm a Geezer) mostly at low rpm, so the stock thermosat is probably a good fit for me. But for those who own XKR's engine heat management is a constant issue, usage of a cooler thermostat is a consideration.

 

Yes, in an effort to fool the computer into richening the mixture. This started in the C4 (1984-96) era where the practice sorta worked kinda sometimes, but not since. It's since turned into one of those legends that people still cling to irrespective of facts.

 

Sorry but I disagree regarding todays technology engines. In yesteryear this was somewhat true but with todays engines and engine management the engines are designed to be most efficient in the 200*F range. The system is designed to run in this range and if it exceeds it then there is a technical problem that needs to be fixed. I don't know the design parameters but my bet is these cars can run all day in stop and go and interstate driving when it's 120*F outside.

 

To go back to the original subject of this particular thread; earlier this week when I started up my 12 XK vert I got a low coolant warning. since I had an appointment to make I hooked up the OBD reader and torque app in order to keep an eye on the temp. I drove to my Dr's appointment about 45 minutes in LA traffic both freeway and street driving. My hope was that the car would run at its normal temp (about 195-202 degrees F.

Well, as I thought the low coolant warning went away after about 7 minutes and the car operated at just a little above normal - about 205 degrees until I got about 5 minutes away from the appointment, then the warning light came back on and the temp climbed up to 212 degrees and stayed there..

When I cam back out about 90 minutes later the low coolant light came on when I started the car.
I drove to my dealer which was about 20 minutes from the Dr's office. When I got to the dealer the temp was 218 degrees. I described the above occurrences to the service advisor and told him I thought the water pump was in the process of failing.

Long story - result, a new updated water pump installed under warranty and no fried engine. You could call this a testimonial to the OBD reader and Torque app. So, all is well that ends well.

 

Do I assume you checked the coolant level and topped it off? Also I believe that for every 1 psig you have on your coolant system pressure cap it raises the boiling point . A 50/50 mix of antifreeze at 1 psig raises the boiling point to around 225*F. With a 15 PSIG pressure cap the boiling point is now around 260* F so your 218*F was not a problem for the engine. If you were running at say 240*F I would start to worry.

 

Jagtoes - The point of my post was that the dealer (and probably Jaguar NA) decided that it was time to replace the water pump under warranty. IMO that is what really counts here.

 

OK so what was the final verdict. When they showed you the old pump could you see or did they point out where the failure was. Were the front bearings/seal the problem and could you see if there was antifreeze coming out of the weep hole. It would be interesting to see some pictures. Did you ask and take the old pump or did they keep it for warranty reasons. I usually get my old parts back just to see how they failed.

 

Changed out the thermostat, all the associated hoses, both the ect sensors, and put on the uprated Bosch intercooler pump over the winter. Car isn't quite ready to be back on the road yet, still dealing with front bumper/grilles (waiting on grilles to show up).

But anyway, I've been running it, topping off coolant levels, etc. The engine temperature now won't get above 205 with the heater on or not. I think it got up to 210 the other day, and I was expecting the cooling fan to come on but it never did. What temp should the fan come on and why won't my engine get hotter than that just sitting and idling in my shop? Been 30 minutes now and I'm still going from 195-200° F.