still overheating after radiator replacement, radiator overheating engine temperature Options

[Terzin1]

Hi all

Last week my radiator cracked at the fill neck. I replaced it with another and that seems to have gone in just fine. It holds fluid without leaks. I also picked up a new thermostat but didn't install it yet.

So... today I filled up the radiator with coolant and went for a test drive. It started to overheat again so I stopped, let it cool a bit and opened the cap to fill it and let the bubbles come out as it ran, heat was on. The reservoir was bubbling up too. I also unplugged the fan sensor so that they could run continuously just to be sure that they weren't part of the problem. Well, the fans work and seemed to slow the pace of the temp gauge rising, but I'm still overheating. Tomorrow I'll swap in a new thermostat. What else should I look for if that doesn't solve the problem?

[Box]

Make sure all of the air is out of the system and that the cap is good. Let it sit and run up to temp with the cap off, preferably at an angle where the front of the car is higher than the rear to help with burping.

This post has been edited by Box: May 21, 2015 - 8:52 PM

[VavAlephVav]

If you let it run like that for a little while, it might take 30 min, every time the fans kick on the coolant level will go down a bit and you can add some more antifreeze to it.
Also make sure the temp control inside is turned all the way to Hot so that the valve to the heater core is open.

My friend said he used to have a system that would pull a vacuum on the radiator and suck the antifreeze into it. Said he bought it just for Toyotas.
If you don't have one then you just have to add a little more at a time and wait for it.

[Bitter]

get one of those radiator burping funnels and use it to keep coolant above the radiator, put the nose of the car up higher than the dash with some jack stands to help get the air out of the engine and heater core.

[Noahwhite2014]

If it doesn't over heat until you start revving the engine it's probably the thermostat

[Box]

Don't forget to massage your hoses.

[Lamont]

Don't forget to massage your hoses.

[Box]

I've always been able to get all the air out by letting it run with the heat on and front elevated, then squeezing the hoses with the cap off. No need for fancy contraptions or black magic.

[richee3]

I doubt if it's the thermostat coincidentally going bad while the radiator was being replaced. More than likely there's just some air stuck in the system, as stated above. The thermostat is easy to replace though and it's better to do it in advance than before it seizes closed and overheats your engine.

[Nial]

I would start with the thermostat, remember with the new one, boil the kettle and put the thermostat into the water, make sure it opens. Just because it's new isn't a guarantee it's working.

I would then look at the water pump, make sure you can see / feel the water circulating, best to do this in between removing the old thermostat and fitting the new one, you don't have to wait for the water to warm up then. Put the thermostat housing back empty and run the engine for a bit, you should be able to feel the water circulating by squeezing the top hose.

While changing the thermostat I would be tempted to give the engine a good flush out, when the thermostat housing is off and thermostat removed, put a garden hose on the pipe and run it until the water runs clear, then drain as much as you can out before replacing with whatever coolant you run.

[Terzin1]

Ok, so old thermostat was not opening. I replaced it with an oem one from toyota and tested it before installing. Thats all good now. I burped the system and even revved it up to heat up the engine. The fans never kicked on and i know they work. It didnt overheat but what makes those fans kick on?

[Nial]

It's hard to get the fans to come on just by letting the car tick over. Take it for a good blast then leave it sat running for a bit......or disconnect the radiator temp sensor or the air conditioning pressure sensor near the bulkhead and the fans will come on if you want to test them.

[Lamont]

Ok, so old thermostat was not opening. I replaced it with an oem one from toyota and tested it before installing. Thats all good now. I burped the system and even revved it up to heat up the engine. The fans never kicked on and i know they work. It didnt overheat but what makes those fans kick on?

There is a switch on the bottom left of the radiator (when you're facing the car) that kicks the fan on when your car gets to a certain temp it then shuts them off once the temp drops. An easy way to test if the switch is working is to unplug it with the engine running. If the fans turn on straight away the switch is working properly most of the time

[Terzin1]

Cool Cool. I just took the car out for a spirited 20 minute drive and revved the heck out of the engine. Upwards of 3k rpms sustained. No overheating. I popped the hood and found the fans did kick on and off.

Here's the story as I see it then: I'm thinking the radiator exploded since the thermostat was stuck shut. Now that both are replaced it looks like the system has re-righted itself (crossing fingers).

I have one more question. Because I was constantly replenishing fluids while troubleshooting, the system is probably 75% distilled water, 25% coolant. Will this be extremely bad?

[Nial]

That should be fine. I highly recommend using Toyota for life red, it's not only a coolant, but it contains rust inhibitors etc to keep your waterways in tip top condition.

[Box]

In warmer climates there's nothing wrong with doing a 70/30 water/coolant mix.