About a week ago I noticed my engine fan remaining on after powering off the '03 STR. I relegated it to the weather.

Two days ago I'm driving and idling for about 15 minutes and I look down to see a 'High Temp Warning' and my needle maxed. I quickly pulled off and allowed the car to cool off until the the fan turned off. I checked under the hood and saw no problems. Coolant resovior was good, no leaks. I suspected a stuck thermostat. I turned the ignition and made a quick bee line home with the heat full blast and the indicator didn't go too far past center.

Yesterday I made the 15 mile trek to a trusted Jaguar mechanic (who to my dismay is ON VACATION) with heater full blast, and about halfway there I was greeted with a 'Low Coolant Warning' with the car slowly getting too hot. I made it to the mechaninc and popped the hood, this time with coolant sprayed on the hood and a busted upper hose (smaller one which goes into the resovior through the top)

The fill-in mechaninc did not think the thermostat was at fault and decided to replace the resovior. The whole system was pressure tested and checked out fine. I picked the car up and drove it hard and heavy back home against my buddy's Audi S4 (a sleeper), and the needle was again creeping steadily past the half under hard acceleration and returning to normal slowly during cruising.

I called the fill-in mechaninc, and he suspects the water pump now, but it seems like a shot in the dark to me rather than a diagnosis. Any ideas?

 

As the hose leaked I don't see why he replaced the reservoir.

It would be good to have some temperature readings taken at the time (e.g. IR probe).
I think the ECT (engine coolant temp) is near the thermostat i.e. not in the engine block. It's both a generic OBD sensor and available via ETM (engineering test mode).
There's no CHT (cyl head temp) sensor on the STR so that can't be used.
But there's EOT (engine oil temp) which may be a guide as to whether you have local overheating. (Sadly, not a generic OBD sensor.)

I'm thinking that block hot may mean bad water pump. (If you have a hot block.)

I guess you could have over-pressure e.g. bad head gasket but from what I gather the water pump is a LOT more likely to fail than the head gasket on the engine (whether 4.2 NA or SC) so don't panic yet.

hmmmm, if it knows it's overheating then ECT is likely to go up alarmingly as you monitor it. To get to the ECT sensor surely you need coolant flow i.e. water pump moving coolant? hmmm (again), maybe working but poorly.

When's the other guy back from vacation? lol

I sent a list of acronyms to a mod some time ago so hope I can stop this pesky and very time-consuming typing soon.

 

Most likely the water pump. install a low temp thermo while in there.

 

August 5th. I may just wait it out, but the pump seems to be everybody's guess

Getting to the water pump possible without dissasembly?? The low temp therm will be dropped in shortly.

 

I agree with jagv8, replacement of reservoir wouldn't be the first on the list in addressing an overheat. An obvious symptom of a blown head gasket is a shaking misfiring low power engine. Have tech. check radiator, water pump, and thermostat.

 

If it turns out it's the water pump, there may be parts of the blades broken off. Would you trust the fill-in guy to find and remove those parts? You don't want them blocking the coolant flow.

 

Why? Is there a know issue for these cars that requires a different thermostat?

 

No. It's a thing some think is a good idea. The "science" looks thin (and for a non-modded STR, looks non-existent)....

 

Stattsoff and jagv8, I'm familiar with ChriSTR's STR as a modified Florida (frequent 90 degree daytime temps.) car. A low temp thermo (185 degree vs 200 degree= stock) is a drop that a soon to be pullied STR may be able to take advantage of, plus we understand a thermostat install is not too complicated and an easily reversable process. While remedying either or all of a "radiator-water pump-thermostat" issue, let's tip Chris off to the "possible benefits of a low temp. thermostat as a means for him and/or all of us to benefit from his experience. A low temp thermostat is available for $35 from Eurotoys. I spoke with the owner of this company and he found it helpful for his own STR. As he increased blower speed he wanted to avoid the ECU's pull back of timing and fuel and minimize the possibility of detonation too. Another member here installed EuroToys low temp thermo and with his laptop was able to see a 15 degree drop in coolant temps.

 

If it works on a modded car, great.

On an unmodded car would it reduce MPG?

What about the intercooler coolant circuit? It won't help cool that, will it? Won't the PCM change the timing because IAT2 reads high?

Acronyms: https://www.jaguarforums.com/forum/a...6&d=1280220450

 

Well that's why I asked. So anecdotally a couple people think this might help with cars that are modified for more HP. That's "Horse Power" ;>))

Hmmm.

It also has been quite warm of late here. Is his car heavily modified or does just the pulley modification put the car on the edge of the cooling system?

From the diagrams I looked at on here the two cooling circuits are connected but the circulation of the coolant in the the two circuits is independent so I'm not sure if much heat flows between the two circuits.
Has anyone ever measured this at load? I would think that Jaguar must have.

Bob S.

 

I believe Chris's STR is modded with a smaller pulley and a few other items. The low temperature thermostat will cool down a hot block which to a degree may cool the blower cooling circuit.