overheating

[madder]

Just idly wondering if there is a radiator core problem here.....does it get universally hot all over?
John

Last few times I drove it, it seemed genuinely hot as soon as I lifted the bonnet. It was bubbling and the coolant reservoir was overfull. But today it seemed normal enough.
Is there any other way(besides squeezing the hoses) to try to get the air out of it, if that's what is causing the waterpump to fail?

 

[Burnerman]

Seriously I would have expected the air to have been expelled by now - especially if the heater is working (normally the first thing to run cold).
So, I have to suspect either a circulation problem (pump) or the lack of ability for the engine to cool itself (radiator).
Pump impellers do fail - VW's especially seem to be prone to this as the pump impeller is plastic - but I've never seen a failed Toyota one.
However, these radiators are remarkably thin, and therefore prone to blocking with rusty deposits. Is it the original radiator?
I'm hoping the cylinder head gasket isn't letting go - but a garage 'sniff' test can identify this one.
John

 

[madder]

A sniff test? I can tell you now that the smell of the coolant that has leaked over the past 2 weeks or so still hasn't cleared up!
Really hope it's not the gasket? I'm not 100% sure if it's the same radiator as always as I only own the car about 4 years. But I'd say it is.
Remember this thread started off with a leak in the radiator, which radweld plus managed to repair. Then the hose got a pinhole and started to leak. I'm awaiting a new top hose from toyota, it could be weeks before I have it. But the rescue tape is doing a great job keeping it sealed. Now the problem has moved on to either the pump, or something preventing the radiator from cooling itself. If there are any tests I can do myself I'm open to giving them a try on someones instructions? Thanks guys, you've been great this far as usual!

 

[Burnerman]

Usually, the signs of head gasket failure are obvious - coolant belching out of the expansion bottle, oil in the coolant water etc. However, I've had vehicles in that would tick over perfectly in the drive for ever, but once out on the open road all hell breaks loose.
I'm just concerned that the Radweld has done too good a job and is restricting water flow around the radiator - I don't know!
That characteristic smell of coolant should have cleared by now, if the leak has stopped.
With the sniff test, the gases above the coolant in the expansion bottle are passed through a blue liquid. If products of combustion are present, the liquid turns yellow. I've never known this test to fail!
It can at least rule head gasket problems out.
John

 

[madder]

I know there are risks with radweld, but I really didn't use very much of it. Less than half of the bottle over a period 2 to 3 weeks. I still have some of it. But I guess with the second leak(the one in the hose) maybe the radweld remained in the cooling system while the water and coolant emptied and then perhaps it blocked up something? It's probably unlikely as Halfords would probably recommend using a full bottle of radweld to fix the leak that I had, and as far as I know it needs air and heat to seal over holes, but it allegedly only seals holes which have air coming through from the outside? I'm also wondering if radweld did block something, for example preventing the pump from working, would that not prevent anything passing between the reservoir and radiator and/or back again. Because fluid does seem to be passing between the two, albeit abnormally.

EDIT: as of now, I'm fairly confident that there is no oil in the coolant expansion tank/reservoir. However, there was coolant and water trying to overflow out of that tank yesterday when I first noticed the thermostat rising.

 

[Burnerman]

So, coolant trying to escape from the expansion bottle has a few causes.
1) Air locks trying to escape - as discussed previously. Often there are bleed points on the top hoses to help with this.
2) Air being constantly admitted to the system, due to porous hoses or castings or a suspect cylinder head gasket.
3) Local boiling of the coolant due to the radiator being unable to do its job or thermostat failure.
4) A malfunctioning water pump, which will give the same symptoms as (3).
Seriously I do suspect the radiator but I don't want you to dash out and buy a new one, but when the engine is hot, feel the entire rad surface if you can - it too should be hot all over.
John

 

[madder]

I'd say it's 3 or 4 also. Gun to my head and I'd probably lean towards 3 as it all seems to get very hot under there.
So if I start the car, let it run for 15 minutes or so, then I should open the bonnet and put my hand on the radiator. If it's working correctly, the full body of the radiator should be......hot? If it's not working correctly, then it's either boiling or cold? I'll maybe do that this evening. Thanks again John

 

[Burnerman]

Take the car for a run, so the thermostat will be fully open, and the heater will be working.
Then, feel the rad surface all over for any cool spots - there shouldn't be any.
The rad will only get hot, naturally, when the thermostat opens - it will be cold until then.
Watch that bloody cooling fan for starting up though!!
John

 

[madder]

I'll do that now John and report back in a while. I will try to test as much as the rad as I can for cold spots and I will be very careful with the fan. Hopefully if there are cold spots, they'll be found before inspecting the area behind the fan!

 

[madder]

Just back from my drive. It heated up very quickly, probably because I was only 2 or 3 hours later than the earlier drive. I couldn't really get my hands near the area of the radiator where the fan sits in front of it, but I'd have to say the bits that I could touch between the fan and the expansion tank, opposite the engine itself seemed hot all over. Certainly no cold spots.
The general feeling when I open the bonnet is one of heat. The Top hose is very hot, and even the slim hose that operates between the top of the rad and the expansion tank seemed very hot. This boiling theory seems like it might be right.

What I don't understand is why the heating on full blast in the car keeps the temperature down? At first I thought it was something to do with the fan at the radiator but this fan works properly with or without the heating in the car turned on.

So it seems to me that as long as I keep the heat blasting in the car, it'll run ok. But what is the fix?

 

[gblades]

The radiator fan will only come on when the water temperature reaches about 85C and with the already hot water entering the engine if the circulation is poor then by the time the water exits the engine it is too hot.
Turning on the heating cools the water a bit more as it exists the engine so by the time it goes round the radiator again it is much cooler. Forcing the radiator fan to be on all the time should accomplish the same thing and avoid you being roasted aswell

 

[madder]

Unfortunately, I don't know how to short out the fan and make it work permanently.
This is looking more and more like a new radiator at the very least and possibly a new pump to go with the new top hose.
I'll have to live with the roasting for a while I'm afraid.

 

[madder]

Just had a couple of thoughts.

1. Could the radiator cap be faulty and would this cause the symptoms I''ve been having?

2. I remember one of the many times I was topping up the radiator and expansion tank recently with the coolant, and as the radiator filled there was some radweld at the top of the coolant just where the cap goes? Could this have slipped into the hose between cap and expansion tank and caused a partial blockage and is there an easy way to find out or test it?

 

[Burnerman]

Just a couple of theories now, and unfortunately none of which will effect a definite cure.....
The radiator gets hot, so that indicates that the thermostat is working, and allowing water to circulate. We don't know if the 'stat is opening fully though.
The purpose of the radiator cap is to keep the coolant under pressure - in this way it raises the boiling point of the liquid to around 120 deg C. This too seems to be in order.
So - the engine is producing too much heat. It doesn't matter how the thing is cooled down, so long as it is - hence the heat dissipation when you turn the heater on.
So - either the coolant can't circulate enough (pump problem) or the rad. can't get rid of the heat (blockage somewhere).
When you lift the bonnet, expect things to be bloody hot (it is summer after all - or supposed to be). All the radiator hoses will be stiff due to the pressure within. Now, at this point - is the engine losing coolant?
John

 

[madder]

The Engine? It could be. Where do I check for that? If it is, it isn't losing very much because it's been consistently at the same level in the expansion tank for a couple of days now?
If the engine is losing coolant where does that leave me? Also, wouldn't radweld deal with that too? Still worried that radweld may have blocked something in the system myself, but it's worth checking the cap too I guess.
I think the thermostat is working properly because the top hose is getting very hot also.