My STR has been overheating, coolant level is okay, everything is fine. I replaced the thermostat but still overheating. burped the system and all. the car sometimes will run fine (around 203F) but sometimes it'll go up to 230 and ill cut it off with the fans on high. I check the temp on my phone. I'm running out of ideas. Bad thermostat? Bad Water Pump? the oil is fine and so is the coolant so i doubt headgasket.

 

Pretty rare so you may struggle for help, sadly. Be afraid though as the heads won't tolerate it

Maybe one of the 2 coolant pumps? I'd be thorough about checking both.

 

1) First thing, please define "overheating". Are you getting steam from under the hood somewhere, loss of power, or any unusual sounds such as knocking, etc.? Or are you only seeing the temperature gauge reading high?

2) Re: The temp on your phone? Are you talking about a scanner display on your phone? That's what I use on my car, but am not quite sure if that is what you mean.


The big question is if your engine is really overheating, or just indicating so. If the temperature sensor was reading high, but the actual coolant temperature was still good, the gauge would show high and the cooling fans would run on high, thinking there was an actual overheat. I'd suggest to beg, borrow, or steal an infrared thermometer and record the temperature at the thermostat housing and at the radiator inlet (upper hose). No whining, you can pick up an el cheapo thermometer for only about $20. They are indispensable for troubleshooting.

Also, please be aware the dashboard temperature gauge is deliberately misleading, as detailed at the following link, so don't rely on it. This is from the XK forum, but the general principle is the same on the S-Type:

https://www.jaguarforums.com/forum/x...e-gauge-62813/


Use a scanner to read the coolant temperature, but compare this value to what you recorded with your infrared thermometer in case the sensor is reading high.

If you find the engine is actually running warm, the first thing I'd suspect is your thermostat. Even though you've just installed a new one, don't assume (Danger! Danger!) it is accurate. I have had several bad right out of the box, both on my S-Type and other vehicles. It's got to the point that I won't install a thermostat without first testing it in a pot of water on the stove. Hopefully you still have the one you replaced. Check that one for accuracy to give you an idea how best to proceed. If you find that thermostat was opening too high, that was probably the original fault and you had the misfortune to replace it with another bad one.

Please let us know what you find and we can walk you through some additional troubleshooting steps.

 

There is no sign of overheating, i’m checking the temperature on my phone as i know the gauge on the dash is next to useless. But no steam, loss of power or nothing. Just the temp goes up and the fans kick on high. I don’t actually think it’s overheating

 

Er... I'd trust the phone (I think you mean OBD II) reading unless I was ABSOLUTELY CERTAIN it wasn't right - because a written off engine isn't nice.

If you get any of the things you describe (steam etc) it's probably too late.

I think if you get a loss of power then it's definitely too late. Don't risk it!

 

Yes, yes, I should have included a warning. When using an infrared thermometer to check the actual temperature, be very careful and keep an eye on what the scanner is reporting. Be prepared to shut the engine off immediately if the actual temperature rises too high.

 

+1 on using an infrared thermometer aimed at the thermostat housing and upper radiator hose.

Just because you replaced the thermostat doesn't mean it isn't faulty. Use the OEM thermostat as the aftermarket ones can often be faulty out of the box.

 

I'm going to grab a infrared thermometer soon (most stores are closed because of the corona scare). And i'm more towards sticking thermostat, because sometimes it'll be good sometimes not. I got a duralast thermostat and i know that it was cheap but i don't live near no dealership. If it is thermostat my two options would be a dealer replacement or eurotoys low temp thermostat. What do y'all think?

 

I tend to like Rock Auto. Used them a few times now and they've been good. Website works really well too. Recently lost my radiator and I've chosen to do nearly the entire system. Radiator, hoses, Tstat, water pump, and belt. Rock Auto had the best prices on everything and I only had to hunt for a couple of hoses on Ebay.

 

I'm staying home myself. I picked up an

IR Thermometer" target="_blank">IR Thermometer

IR Thermometer">IR Thermometer" /> IR Thermometer">IR Thermometer

from Amazon back in '15 mostly for tire temperature checks on my Arctic Fox but have used this on many other things including engine related items. This replaced another one that went on permanent loan somewhere. I think the first one I bought was probably near 14-15 years ago. Great tool for < $20.

Back to morning brew . . .

 

hi
every time Ive seen one of these overheat for no reason, its usually head gasket
get a sniff test to confirm
cheers
joe

 

I doubt it’s a head gasket. i drove around today and it rode perfectly fine. i’m towards a sticking thermostat which will go every now and then. But head gasket? how ? explain more...

 

Replace the thermostat, refill and bleed the cooling system. If there are signs of coolant loss once the system is bled, further diagnosis is needed.

 

Got you i’ll come back with more info after

 

should it matter what position the thermostat jiggle valve should be? i’ve heard that it should be at the 12 o’ clock position i think i didn’t do that? either way the new thermostat comes in tomorrow morning so just install in the 12 i clock position or it shouldn’t matter?

 

Yes, position the valve on the top so trapped air can escape from the hoses.

 

Put in a new thermostat today. Put coolant in and drove it and it immediately overheated. came back home and burped the system and then i drove again and it was around the 204-210 range and it would creep up until i gave it gas and would come back down. I was wondering to drive the car without the thermostat and see how it runs. is the possible?

 

drove it and bled it twice more and it goes from 204 to up to 215-217. i’m not driving far. maybe a block. starting to think my water pump as i hear a pulley going idk. starting to also hate the smell of coolant. any thoughts of not using the thermostat?

 

took thermostat off and all it did was heat up even quicker!!!

 

Careful, you'll kill it.