Live4brew

Fellas, thanks to some threads here, I learned how to bleed my coolant system after a thermostat replacement (should have learned long ago....I"ve had this 98 since 04 lol).

Anyhow... I'm still having weird issues. The reason I thought I needed a new thermostat was because my car was overheating in traffic, especially with the AC on. Otherwise, it ran at normal temp.

After replacing thermo and bleeding the system (or, attempting to, anyhow), I noticed a few weird things.. when test driving with the heat on full blast, I got plenty of very hot air coming out. When I'd come to a stop however (again, with heat on full blast), I would get luke warm to ambient temperature air coming out (and you'd think the air would be hotter at a stop!?).

When I ran the AC in park (keep in mind the temp outside wasn't all that warm at 75 degrees F), the temp gauge would rise more than normal, but far from the red zone as it did before I changed the thermostat.

Any thoughts??

LScowboyLS

the heated air will not be hotter at a stop (engine is at idle)

also, did you pay attention to the orientation of the thermostat when installing (bleed hole up)?

if you have over 200K miles, it is likely you need a new radiator - they eventually clog up!

Live4brew

I did NOT pay attention to this. I'll have to pull it back off. What is the function of that bleed hole?

RA40

iTrader: (6)

Check for debris between the A/C condenser and radiator. Leaves find their way in there and if you have a collection, it can be a significant disruption of air passing through the radiator.

Live4brew

I pulled the thermostat housing off to see where the bleeder hole was...but the thermo fell off before I could take notice. I oriented the hole upward and put everything back together.

I left the bleeder valve off as the car warmed up to temperature ... but never noticed (that I could tell) fluid moving. The operating temperature was holding steady at normal levels, however.

When I turned the AC on full blast, the temperature rose quite a bit above normal...but I never saw the auxiliary electric fan on the condenser unit kick on.... At what point should this fan come on?

Live4brew

Thanks, checked and looked very clean of debris. I'm wondering if there is a blockage in the radiator now. I do have over 225k miles on the radiator...

Live4brew

I'm thinking that the system just isn't getting bled ... no coolant is being pulled back in from the reservoir, even though I've changed the thermostat twice now (to orient the air hole) - there was coolant loss in the process, but didn't notice the level change in the reservoir.

Any thoughts?

Yamae

Replaced the thermostat because of overheating?
That is strange to me. You may have your reason that you did so but I have never experienced the overheat caused by the aged thermostat.

Aged thermostats tend to open the gate due to the reason that the wax inside is missing a little by little and it causes the bigger water flow even at low temperature conditions. This is surely the over cooling. In the past, I have replaced nearly 15 thermostats and all the reasons were longer time to warm up or over cooling.

Your overheat might be caused by some other reasons, I guess. Judging from your posts, the water flow is not very good. Something is blocking it or the water pump not functioning properly. Clogged radiator might be the another reason to consider.

LScowboyLS

I agree with Yamae - clogged radiator or water pump broken (like blades broken etc.) would be good suspects

the radiator is not that expensive and a great idea to change at 200K anyway, that would be the first thing I would do after replacing the thermostat - both are very easy repairs!

PS - I am not a fan of cleaning a radiator internally i.e. "having it boiled", this never does much, just replace it, much better for several reasons!

PS2 - if you replaced the thermostat, you did use the real Toyota part, right? - also, I would insist on the real Toyota radiator and avoid aftermarket unless I was in a real financial bind.

JEL

Koyo is probably the only aftermarket radiator I'd trust. But I believe partsgeek has Denso radiators pretty cheap compared to the dealers. I also think replacing it at 200k is a good idea.

Live4brew

Definitely looking like a blockage somewhere. The temperature, at times, fluctuates too quickly (according to the gauge), I don't think the water temperature could change that fast...I'm thinking steam to water to steam (air in the system).

KA8

iTrader: (1)

Does it overheat with AC OFF? If it doesn't overheat w/o ac but does with ac on, and aux fan doesn't come on there is your problem. I went through similar issues with my Z recently. It used to overheat in traffic/idle ONLY when AC was ON. I replaced whole bunch of other things and it came down to burnt aux fan(I blame previous owner for ghetto rigging with aux fan relays). Ever since then it's been good.

Lexinky

You could test the fan by unplugging or jumping the switch on the radiator. It is locate on the left( drivers side ) lower corner.

I can't remember if unplugging it or jumping the connector made the fan run, but I tested mine this way. It should runat high speed

The fan also runs at low speed when the A/C high side pressure reaches a certain level. If the system is low on freon it may not ever run.

I could easily see coolant flow in mine with the ( fill/ bleed ) plug near the radiator hose removed.