Had my car for several thousand miles now. Never had any overheat issues. From 90-degree weather. Highway speeds or idle in traffic. Never an issue. Took a ride yesterday. No trouble on the ride. Pulled in the garage and shut it off. Could hear fluid leaking. Then the bubbling/boiling/gurgling really started. When finally cooled had a pond of coolant on the floor. About the size of the car. It really dumped the system. Going to start with the thermostat. From what I see the car has a newer aluminum core cross flow replacement radiator. Fan clutch appears newer too. Water pump is unpainted. Yet has plenty of patina. So changed at some point. Just wondering what might cause such a sudden issue. It's been great until yesterday. Alos wonder about overheat dash light. It did not signal overheating. I checked the light today. Grounded the wire. Dash light lit as it should. Question there should overheat light come on when first starting vehicle? Like oil pressure and charge light do? Overheat dash light has never lit at start up. Only lit when I grounded the wire. Have a new stat and temp sensor on the way. What a mess on the garage floor to clean. Did it just have a stat failure?
I don’t see what would indicate you have a tstat issue? If it wasn’t opening I would expect issues before you shut it off… not after. I would start with a fresh radiator cap if yours is older.
Check or replace your radiator cap. Upon shut down the cooling system temp goes up so does pressure, if the cap can’t hold system pressure (15/16 pounds) the cooling system will push past the spring loaded rubber gasket, fill your overflow then when that’s full spill onto the ground.
I'll give a new cap a try. It looks really new. Like it may have been replaced when the radiator was. Still going to replace the temp sender and stat while the system is near empty.
You should invest in a real set of gauges so you know how hot the engine is running. Water boils at 212* F at sea level, less at altitude. Ethylene Glycol Anti Freeze mixed 50/50 with water raises that to just 223*. The majority of boiling point elevation is accomplished with pressure. For every pound of pressure, the boiling point is elevated 3*. That means a 15 psi cap elevates the boiling point 45*. I would install a temperature gauge and replace the radiator cap. Replacing the thermostat might be a good idea as well.
Here is an update on the overheating. First thing I did was remove the rad cap to observe a full radiator. Despite what was belched out of the system the first time. So I went for a couple more long rides. Had no issues at all. On the third time out it was boiling over at a stop light. Made it home where it erupted again. I changed the stat. Refilled the system. It took several tries to get the system full. Been using the car for several days now. It seems all is well again. I never did change the radiator cap. I will install the new cap later when I drain system. I just filled with water in case it boiled over again. I'll drain and add antifreeze once it keeps it cool for a bit longer. I missed my big buddy when he was out of service. Had a fabulous drive around the lake this morning with the top down!! Glad he's rolling again.
It sounds like you might be over filling it? You realize the "full" isn't all the way up to the cap? Maybe set up an overflow bottle.
Even without a coolant overflow, the cap (in proper working order) will relieve excess coolant due to expansion and "self correct" if overfilled. This also requires a system with no loss of pressure due to leaking hoses, heater core, radiator or "gasketed" surfaces. A leaking system can be realized by the overflow tank becoming empty over short time, due to the tank contents being pulled into the cooling system when the car cools off, and the "lost coolant" keeps that cycle ongoing until the overflow tank is emptied. Many times such coolant leaks are so small they do not leave evidence, so the coolant tank is a good indicator of something needing attention. If system pressure is not existing over atmospheric, you will see "overflow/boilover" on most any high temp days, and the first "warning" may well be the "boil over" on shutdown, as the OP observed. Temp light can be tested by touching the sender wire to ground with key on. The sender is a "normally open" switch, that "closes" (grounds) the temp light circuit when hot. The "test" circuit energizes the temp lite using a set of contacts in the ignition switch that grounds during start, then returns open when engine is running.
Your autoparts store can loan you a sort of bicycle pump with a gauge on it. You fasten it in place of the radiator cap, and pump the system up to pressure and then wait to see if leaks away. This will help you find your leak with a cold system.
No Jason . The TEST to see if the bulb illuminates is to have the key in the CRANK POSITION no matter the temperature . lol
Mine has been useful. Driving down the road, light comes on. Stop immediately. See that upper radiator hose has split and is leaking. Cut the hose back to good material, reattached. Added some warm tap water. Back on the road. Sure, I added a gauge after that experience. But the light did in fact work. Now the oil pressure idiot light on the other hand, is truly useless. It should say "too late!"
I was answering the original posters question as to when the light would illuminate so as to test it .
I followed the old adage. When all else fails. Read the directions. Dug out the owner's manual and shop manual. Here is what I found out. Factory info confirmed that when filling cooling system, the radiator is filled to the top of the neck. Once full the cap is installed. All other checks or fluid adds are to be done at the built in recovery tank in the fan shroud. My tank is intact, not leaking and functional. Manuals said to idle engine when filling till upper rad hose gets hot. I did not do this because with the cap off, system kept pushing coolant out of the rad neck. So I replaced cap. Drove until warm. Let cool off. Radiator was now down considerable amount. Aprox 2 qts. Fill to top Repeat drive/cool cycle. Add 2 more qts. took 3 cycles to get system to where rad was full to top of neck before and after heat/cool cycle. I then filled recovery tank about halfway. What I found interesting was that the recovery tank level should be checked after vehicle is driven and fully warmed up. Once parked level in tank should be checked when warm. Level in tank should be aprox half way between full and add marks on tank. Adding fluid to the tank to bring to full mark on tank. With the system cold. Can indeed overfill system. Causing a spillover at engine shutdown should the system send overflow into tank. I think my vehicle had a stat starting to fail as it's problem. The last trip I took before changing the stat. The car boiled over at a stoplight. It had never done that before. All boil overs prior occurred at home right after being parked. Since replacing the stat I've got about 200 miles on the replacement. At various speeds and outside temps. With no issue yet with any boil overs. The shop manual specifies the temp sensor to trip at 253 degrees. I will install the new one I purchased when I drain system to install antifreeze before I put the car away for winter. In the meantime, I will watch coolant level in the tank when warm. Hopefully to drive more with no repeat boil over issues. I really dislike the look of aftermarket under dash gauges in a luxury type vehicle. However I may figure a way to do so. I want to fit small custom console to house a CD player, cup holders, and now possibly a temp and oil pressure gauge.
Sounds like you are on the right track . I always raise the idle speed when filling and let it " Burp " once or twice . The " HOT " light might come on at 253 degree but I believe the " STOP ENGINE " light doesn't come on until around 265 degrees . Check your shop manual on that one . Enjoy your ride .
Don't fill the radiator to the top. It will just belch half of your coolant on the ground. Fill it half way up and start the car. When the thermostat opens, you'll see coolant flowing through the tubes. Then top it off and install the cap with the engine running. Top off the reservoir. Done.
