and it's random and it's not cause of any leak and all the components of the system:hoses,, pump, belt, thermostat, gaskets, coolant tower, valley hoses, etc....
are good, what is happening? sensors either work or they don't.

I replaced the coolant expansion tank, bad sensor, leak from underneath...then needed help with a metal keeper for the firewall plug which is impossible to find new and you need to get a fuel injector plug that may work,etc......thanks to a forum member I was able to get a clip....so car fixed...no more issue with low coolant....

NOT

after about 20 min: temp gauge which nobody but me trusts, goes into red, light comes on...but no message on screen...

you all know by now that the computers tell you of every little issue on the screen, except why it doesn't pass smog....drive it enough and it will pass smog.

so it over heated and did not over heat...

THE SYSTEM needs to be burped of air...that's all, I hope....

so if you replace any part of the cooling system, loose coolant, you will need to burp the system, it's a must, otherwise you can get an intermittent over heating that is not overheating as we know it. the gauge works, although many don't trust it, i have had over heating on this car and the gauge works...that's another thread.

oh... no head gasket issues no foam in the oil ...no melting of the aluminum engine ....

oh, i carry tools everywhere i go, it's that trustworthy a car, and i Love IT....and i thank this forum for all the good experience shared with me...

 

ok,, here i thought i had it licked....no
went for a test run of 20 min, no issues, then today a city run of 2 miles, park it, then another 3 miles, then it goes berserk...the car is not hot, there is no message, but the guage all of a sudden climbs from 1/2 way(normal) to red in 20 seconds and the red light on the top of the guage goes on....

what it happening???? does it need more burping, can't imagine it does. WTF???

 

weird as this is a very easy car to bleed. with the cap off the plastic header tank fill through the tower until both are just at overflow. install both caps fill the overflow tank in the right fender to 3/4. start the engine and after it warms to about 185 turn on the cabin heater. turn off the heater after about ten minutes and let the engine run until the cooling fans come on. shutdown and let the engine cool to ambient temp or overnight. check the header tank to make sure that it is full to the top. if not, top off and make sure that the overflow is at least half full. it will form a siphon and rise and fall with the expansion of the fluid and keep the header tank air free. use the car or run to hot and after cool down check the header tank again.

the only thing that might help you troubleshoot your situation is removing the thermostat and doing the above procedure and using the car. it might simply be a sticking thermostat. the cooling system will fill with the thermostat closed no problem. just look at the position of the upper radiator hose to verify this.

another possibility is that different types of coolant were mixed and caused a super clog in the system, most probably the radiator.

 

Some tricks I use in my shop:

Air always works its way "up" in a cooling system. I have jacked up the front of cars to help move air from the engine to the radiator where it can be expelled.

As the car comes up to temperature, with the cap off, you can burp a cooling system by squeezing the upper and/or lower radiator hoses (carefully).

Increasing the engine rpm will help push air out of a system -- basically rev on it a bit.

As much as you trust a temperature gauge, invest in a laser temperature gun and use it to check temps -- the thermostat housing, hoses, radiator, etc...

 

 

Is the thermostat in backwards? It's possible to do.

 

No one has advised doing a pressure test on the cooling system?? You should NEVER trust the temp gauge in these cars. The car is over heated before that gauge tells you. Most everyone in this forum will agree.

 

thank you all for your advise. i have burped the system for sure, it's so random. all i did was change the expansion tank with sensor, drain coolant required to do so,, replaced coolant and after about 20 min it goes berserk in a matter of seconds. turn it off and it goes down, start out again it goes up in a matter of seconds or minutes. no signs of coolant leak anyplace, heater works well....its random that's what gets to me.

now i think i may have to turn to some shop in my area, last time i did that was a mistake. someone has a recommendation, i am in redwood city, ca.

 

Do a pressure test. May not leak while running where you can see it. Cold, pressure test will reveal a leak. Worst case is a head gasket???

 

The sudden spiking temp suggest a defective thermostat. If the fans were not engaging it would be more of a slow temperature rise up into the danger zone. Also, if the car is being driven at anything over 20 mph the airflow through the radiator, even without the fans running, would likely keep the coolant temp within range. Easy to check fan operation though and a laser temperature gun is ideal for this to check for proper engagement. Also, activating the AC should engage the fans and this can be the back up test to determine if that then brings the coolant temp down.

Adding to the list of tricks - most modern thermostats have a small air bleed built into them. Basically a hole with a little stopper that allows air to escape from the engine side of the thermostat. As posted, if the thermostat is installed backwards the air bleed may not work. If the thermostat does not have an air bleed, a strategically placed 1/8" hole in the side of the flat plate portion will also work to bleed air. If the thermostat is mounted vertical, rotate it so that the air bleed is at the top. If horizontal, rotate it so that it is at the higher side of the mounting base (if there is any appreciable slope).

 

Thank you all for your input, I do appreciate the thoughts....WHAT I NEED IS FOR someone with the exact same symptoms to chime in what their fix was???

the thermostat was installed 2016 or so, and has never been an issue....I know it seems like it is the thermostat, I just want to believe it did not coincidentally go out at the same time as the expansion tank began to leak, and there car never lost more than a 1/2 glass of coolant at most....i am going to do another bleed of the system, with a kit I just got with a large funnel and related fittings for just this thing.

 

Is there a special reason for having two threads covering the same problem?

 

the same symptoms could be caused by different problems. this is why we are suggesting various troubleshooting procedures. in this spirit it is suggested that you try a run without the thermostat in place. after that, it is possible that the water pump has deteriorated. is it the original. after this, then your problem might be a clog somewhere.

 

A blockage, or even a hose that is collapsing once the thermostat opens, would certainly explain the symptoms described by the OP. I agree that removing the thermostat would rule it out in a hurry, although that will usually set a check engine light when the engine does not come up to normal operating temperature within the expected time frame. If the thermostat is removed it can be tested by suspending it in a pan of water (usually with a piece of wire coat hanger or even a large paper clip) on the stove using a kitchen thermometer. As the water comes up to the thermostat's rated temperature it should begin to open and then be fully open within a degree or three of the rated temp.

 

yes, however there was a dual purpose to my recommendation. it would have eliminated any bleeding issues and completely purged the system at startup.

not that this is a difficult system to fill based on experience. he has a flow issue, no doubt, either pump or blockage(s).

 

ok, today i got my large funnel burping kit, burped allot of of air.
took car on 45 min trip, all good till...30 min in.....i went on an on ramp with lots of elevation, punched it to merg, heating came back and went away...
came back again and went away....by the time i got home it was pegged....turned it off, it was immediately fine.


more burping, lots of it...coolant tank sounds like a peculator making coffee.


no more over heating, but coolant level is low in message center...so i just parked it for now....
i have been putting in fresh coolant when it burps some of it out.
but there is more ramdom behavior....not what would happen with a bad thermostat, pump, etc....somehow massive amounts of air trapped way in system come out when car drives uphill for a length of time or fast around an on ramp....

still runs like a champ smooth, after 1/2 hour of steady idle too....coolant fans work fine. a/c works, heater is great.

 

If you do decide to take it to a local shop, try Hills Motors in San Mateo. They are open Mondays, Tuesdays and Wednesdays. They have a couple of decades under their belts working on English cars, mostly Jaguars these days. I've been using them for the past 5 months since I purchased my 99 XK8.

 

Some engines are notoriously difficult to purge air out of the cooling system after it has been serviced, however, by Cor's post above that does not seem to be the case here.

To my knowledge, the only way air can be induced into a pressurized cooling system after it has been bled and filled is by an air source with higher pressure. This would unfortunately mean a blown head gasket. Sincerely hope this is not the underlying issue. Although a minor head gasket leak can be difficult to detect, your two most common methods of detection are the presence of white smoke in the exhaust - usually accompanied by the sweet odor of coolant, or the presence of a clean spark plug - one that essentially looks like you just removed it new from the box without any tan or black carbon buildup on the electrode or ceramic insulator. Obviously, this entails removal and inspection of all of the spark plugs.

 

this might be an easier way, see video below:

 

Absolutely agree... but most guys don't have that tool in their garage. This being said, they can be rented from the major parts chains.