not deaf ears. Just want to try the little things before I spend hundreds on a water pump. I appreciate all the advice I have received.

 

New update. I did replace the thermostat and fired up the car for a test drive. Once again it over heated. So I decided to pressure check the system again to see if I still held up to previous checks and try to listen for any leaks in the system. As I was looking over all the hoses trying to listen for any leaks I notice something important. The aux pump WASN'T PLUGGED IN!! So I plugged it in and took it for a drive. I wont say problem solved but things improved greatly. Now the car will keep a temp right at 210*. I know that is to high so I will have to look into whats going on. I drove the car for 30-35 mins and got a low coolant light. Well it turns out a hose was rubbing on the belt and it put a pin hole leak in the hose. Now I will fix that and problem and see where it goes.

 

Fixed my leaking hose last night and flushed my coolant system again to make sure it was 100% correct. Didn't bleed the system yet but took the car for a drive and again it runs around 210*. Cant for the life of me come up with a good reason that it would run 10-15* hotter than it should. I have a thermo temp gun and the hoses coming out of the radiator run around 140-150* so I would think that is good temps from the radiator. Anyone think of anything? My thermostat is a 183* like it is supposed to be.

 

I'm a C (rather than F) man really but 210 may be fine. It wants to run hotter than many cars in the past (improves emissions & mpg).

JTIS / workshop manual looks to say up to 216... have a look - free download.

 

+1 on downloading and using the Workshop Manual - http://jagrepair.com/images/AutoRepa...M-Workshop.pdf

From the Workshop Manual:

On the 4.2L supercharged engine the thermostat begins to open at 84°C (183°F) and is fully open at 98°C (208°F).

Factory thermostats are rated on Celsius temperature scale.

 

 

I think they fitted the aux pump to the V8 specifically because it is needed

(As is the IC / SC pump - yes, another pump - on the STR.)

 

I'm still scratching my head on this one. See post #16 for an excerpt from a factory training manual, describing when the pump is commanded to run. The pump doesn't even appear to be commanded on during an overheat with the engine running. The only time it runs if hot is AFTER shutdown:

Auxiliary Coolant Pump Details

Who knows, maybe that was only preliminary information. Perhaps the logic was tweaked before production started. See post #17, where a new aux pump also cured an overheat condition. Maybe we've discovered something new, in contradiction of the training manual.

How about this cheap and easy test? A cooling system in good working order, under normal circumstances, should not require the extra cooling capacity of the heater circuit. On a warm day, if heat is being commanded via the heater core, that means the rest of the cooling system is taxed beyond capacity. That could mean the cooling system can't transfer a normal amount of heat from the engine, the engine is making too much heat, or a combination thereof. Regardless, if all is well, the heater should be fully off on a warm day. If my reasoning is correct (always is... ), switch off the AC button to turn off the compressor. If the duct temperature rises above ambient, you've still got a problem. Heat is being expelled via the heater core, which shouldn't happen on a warm day.

 

hmm, post #17 is not about the 4.2 so the described logic may well not apply.

Also, they could readily have added some extra times it's put on without actually contradicting the page (it would be an omission, to be picky).

 

I'm curious if this has been resolved? I've been fighting a p0328 bank1 knock code. It'll only flash in the early morning and it's a quick flash w/ restricted performance. The light disappears immediately and only repeats this for maybe one mile. After the engine starts to warm up everything is good.

I did get an engine code for the knock sensor after enough pendings and went to clear it. While doing so I noticed my ECT was running a tad over 200F, but didn't go higher than 210F. I'm thinking my DCCV is ok (needs to be replaced due to just cool ac), as when I turn it on the temp drops down 5F to 10F degrees Just too ironic the same code showed up and the same overheat situation.

Humor me..
My thoughts are can the valley hose under the supercharger have a slight leak..? Possibly contaminating the bank 1 knock sensor. But I would think as the system builds pressure more coolant would escape and the smell of coolant would be present. I'll start with the thermostat after I test it in the pot of water. Next I'll go burp the system and replace some of the coolant with water (replaced the orange stuff when the radiator was off). I did replace the radiator a month ago as well as the supercharger radiator intercooler and oil cooler. Temps have been great since then until now. 200F to 210F just seems high to me...

 

For my knock sensor I just ran a bunch of fuel cleaner and new high octane fuel a few tanks. Then disconnected the battery overnight and it never came back. My coolant temps are still a little high. Average around 210F. Not sure why but I do still have a missfire so I think it has to do with that.

 

Is the misfire more noticeable at cold startup or at operating temp? I'll try some cleaner on the injectors. A misfire can cause a slight temperature increase, not sure if 15F over normal would be due to that. Also what fluid are you using for coolant? I flushed out the ford orange and went green..

Had temp issues in my truck, k3500 with a 454, and did the same with changing over gm orange to the 50 50 mix. Added wetter water and a 185 t-stat and runs 183. Even has the clutch fans which suck. It does get up to 200 when sitting still with the ac on. The 7.4l vortec 454s are notorious for running hot. I did go through 2 new thermostats that were faulty. As recommended above definitely test those before installing them. They should always start the open 5 to 10 degrees prior the temperature rating. It's worth the definite knowledge that your thermostat is working properly.

 

Interesting thread. Seems to be a case of slowly chipping away at multiple small faults. Have you tried replacing the coolant temperature sensor yet? If that was out of tolerance, that could explain the slightly elevated reading. Might be worth a gamble.


What are the misfire symptoms? Are you getting the check engine light and an actual OBD code for a misfire? Or just rough running? From my limited experience, the computer has a much more sensitive system than my SOP (Seat Of Pants) detector. On the other hand, my car often runs roughly for about 15 seconds after a cold start, yet that never gets flagged as a misfire. I think the computer may need to see the misfire for at least X amount of time to help eliminate false alarms, but I'm just guessing.

But I do know the computer can detect subtle misfires that I would not notice otherwise. So if your SOP detector is saying misfire, but the computer isnt... I had a '96 Lincoln that felt like it was misfiring, yet it set no codes. Turns out it was the transmission. A new filter and fresh fluid took care of what felt exactly like a misfire according to my SOP detector.

 

My S-Type was randomly overheating last week. I changed the thermostat and a day or two later the oil cooler blew up and the car won't start now as it has no compression. The roadside recovery mechanic (AA) said "the oil cooler exploded" and it lost all oil and water in about 50 metres at 70mph. Do I need a new engine or is there something obvious I can check? I posted this question in another thread but thought I'd add my comment here too. For anyone with an S Type that overheats randomly, calms down when radiator is topped up, and overheats again at a random later interval I suggest checking the hoses near to / connected to the oil cooler. I think I may need another engine in my poorly baby :-(

 

Never been reported before?
Can you post pictures of the blown up oil cooler?
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i have the same problem 2008 jag s type did the over heating ever get fixed i just changed my water pump and still overheating

 

I have 2008 jag s type I have same problem over heating in the weirdest way I just replaced my water pump and still over heats when I drive it