RowenaF

I am a noob, but I did an advanced search, and didn't see much help on this issue. So here goes:
I had previously had overheating issues with the car, but through a series of events ended up replacing the fan shroud/relay? on the radiator. Since then there has been no issues. Just this week the water pump goes bad and as a result overheats and the radiator cracks. We replaced/new: water pump, timing belt, temp sensor, radiator. Cap is fairly new. I get the car back today...mechanic ran it on idle for 30 minutes no prob, but as soon as I got in on the road it started to overheat and puke overflow. After cooling I refilled and let run for 20 minutes for air pockets...no prob. No white smoke or smells, lower hose/top hose are warm/hot, but I noticed that heater is not hot. Could a stuck thermostat cause overheating?

StuckInVA

If your thermostat is stuck closed then yes, it will cause your vehicle to overheat. If your mechanic let the car idle for 30 minutes from cold it might not have had enough time get to the point where the stat should open. Engines heat up much slower when they idle as opposed to having a load. you might notice this if you warm your car in the winter before driving. If it has been a while i would replace the thermostat anyway as it is not an expensive part, however I would be skeptical this is the problem if you are certain that the car will not over heat on idle. Perhaps the thermostat will only open partially? perhaps the cooling fan has enough of a cooling effect on it's own to prevent an overheat under such small load?

(Bottom line, I'd replace it, cheap and will give you peace of mind.) if you really don't have the money, then there is a way to test them by heating them in a pot of boiling water. although I'm not certain exactly how far it should open.

You'll have to drain the coolant out to take the Tstat out, it gives a perfect opportunity to flush the cooling system.

PFB

[QUOTE=................, but I noticed that heater is not hot. Could a stuck thermostat cause overheating?[/QUOTE]



You probably still have an air pocket in the cooling system. Run it in Park, at around 2,500RPM for about 10-15 Min. with the Radiator cap off, and the heater set to full heat.

Make sure that you don't let it overheat while your doing that.

Phil

RowenaF

so I removed the rad. cap and ran for a while with heat on. I noticed the heater got hot. Took it on the road for the real test and so far so good. Now can this happen again? Will more air pockets occur, and how do they cause the overheat and puke? Thanks for the quick replies!

PFB

Drive the car normally for the next week or so, and turn your heat on several times for 10 Min at a time during that period. See if everything is ok. If a bit more air comes out you will need to top up with more coolant as necessary. Check your coolant level when the engine is stone cold.

Youll probably be ok, but if it starts overheating again let us know.

Phillip

JonnysES

Don't forget you have to run the heat in the es in order for it to kick in. If you look by the brake booster there is a little valve that switches coolant flow on or off for the heater core. So that could be weird with your heat. Air pockets could cause this, as well as a stuck or weak thermostat. Make sure your fan is running when the car gets hot, might have an issues with the P/S selenoid that controls the fan or the fan ecu it self or one of the 3 colant sensors, the one closest to the thermastat controls the fan. The two by the radiator cap are for temp sensing alone ecu and gauge reporting.

RowenaF

so it o/h again and i checked coolant (which was low). will let cool and top off and repeat. I may have to do this several times it seems. Weird, I ran around town with a/c on and no prob, then all of a sudden it starts to rise temp and puke coolant.

JonnysES

Have you put a thermostat in the car yet?

PFB

You may have to do that for a few days to get rid of any remaining trapped air.

You also mentioned that you changed your radiator cap not long ago. Did you get an original Lexus/ Toyota radiator cap, or an aftermarket one? If an aftermarket radiator cap, than get an original cap.

Just make sure that you don't let the car overheat.


Phil

moonphase

All other details aside, when it first overheated and cracked the radiator, I wonder if it also blew the head gasket or cracked the head?

RowenaF

We checked the tstat and found it to be good right at 180 degrees...checked the heater core valve and mechanic said it looked suspect with possible leaking. So we are replacing that and will run for a day or so. No cracked heads that we know of. Aftermkt rad cap, but it seems to be holding pressure that way it lets steam out when it o/h.

PFB

Don't take a chance with your aftermarket radiator cap. Get an OEM one right away. It may not be holding the specified pressure, which will lead to overheating. They are notorious for doing that.

Also, how did your mechanic determine that your heater core valve is possibly leaking? If after a few days you still notice that you are losing coolant, than get a coolant leak dye or have your mechanic add it to yur coolant. You'll than be able to find the source of any external coolant leaks with ease.

Don't change any other components (except for the radiator cap) until you do that.


Phil

RowenaF

So, I am assuming that a properly maintained cooling system will not have any (steam etc) leaks? How much is too much leaking? Mechanic saw possible "stains" that may indicate leaking from heater core valve.

PFB

You probably still have some air in the system, which should come out over the next few days. A properly maintained engine should not have ANY leaks. For now don't do anything except change the Radiator cap back to an OEM cap, and monitor your coolant level and temperature readings for the next few days.

So at this point, don't spend any money on changing a Heater core valve that may, or may not be leaking.

Phil

JonnysES

The reason I said that is because I've seen them get stuck closed even after opening and closing several times and on occasion they won't open far enough when the glow needs to go up and it's a really cheap part to replace even for an OEM T-stat since all else is new I would change it anyway just saying. Had a 93 5sfe camry that I worked on for a friend that overheated like crazy everything new except a t-stat I pulled it boiled it in in some water with a thermometer and it opened up around 175 but wouldn't open all the way even after putting a bunch of salt in the water to get it even hotter.

At this point, it's either air, radiator cap(most likely), or a T-stat 3 small things that valve should be cheap but don't usually go bad.