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Well, it's been over a decade since I owned an IS300 but I'm back....this time, not for me, but for a friend.

My friend has an auto first gen that's overheating. He bought it used and it's fairly junky (180k on the clock) but it's a beater car while he saves some money so that's par for the course. Unfortunately, the car has some cooling issues. After tearing into the car we noticed it did NOT have a thermostat installed. This would lead me to believe the car should run too COLD, not too hot....correct? We installed a thermostat and drained/refilled with coolant. The drained coolant was extremely brown and discolored. Burped the system by having the nose of the car in the air and using a Lisle Funnel as a reservoir and squeezing the lower radiator hose repeatedly to push bubbles out of the system. Ran the car up to operating temp with the funnel still connected to the radiator neck expecting a lot of bubbles to come out of the system...never really happened. The coolant in the funnel didn't really get that turbulent even when he revved the engine a bit. We capped it and took it for a spin. Car still overheats.

Some observations....even when the temp gauge is getting into the hot territory, the radiator still feels cool. I touched the top rad hose (from the engine) and it was very hot which I believe to be normal. The bottom hose (outflow) was room temperature. Now, I know the bottom hose should be coolER than the top hose, but it should still be pretty hot; especially on a car that's currently overheating. Another observation is that the heater in the car NEVER gets even remotely warm.

I suspect one of two things is going on. 1) The radiator is clogged or there's an obstruction somewhere or 2) The water pump just isn't moving coolant around well.

Does any of this sound familiar to some of you? Any ideas? Thanks in advance.
 

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I suspect one of two things is going on. 1) The radiator is clogged or there's an obstruction somewhere or 2) The water pump just isn't moving coolant around well.
Thats where i would be starting as well, back flushing the radiator or maybe getting another.

Then i would be looking at the water pump. I have seen a photo of a Toyota from the local dealership here of a 1J/2J Celcior or something like that where the overheating was caused by the water pump having the fins worn/corroded off, apparently it had never been changed despite the cam belt having been changed and it looked like the coolant was the OEM 25 years on so had gone off and not stopped it all rusting. Not saying that is the cause here but it wouldn't surprise me if the pump is worn and cant do its job. But i would start with the radiator first.
 

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Well, it's been over a decade since I owned an IS300 but I'm back....this time, not for me, but for a friend.

My friend has an auto first gen that's overheating. He bought it used and it's fairly junky (180k on the clock) but it's a beater car while he saves some money so that's par for the course. Unfortunately, the car has some cooling issues. After tearing into the car we noticed it did NOT have a thermostat installed. This would lead me to believe the car should run too COLD, not too hot....correct? We installed a thermostat and drained/refilled with coolant. The drained coolant was extremely brown and discolored. Burped the system by having the nose of the car in the air and using a Lisle Funnel as a reservoir and squeezing the lower radiator hose repeatedly to push bubbles out of the system. Ran the car up to operating temp with the funnel still connected to the radiator neck expecting a lot of bubbles to come out of the system...never really happened. The coolant in the funnel didn't really get that turbulent even when he revved the engine a bit. We capped it and took it for a spin. Car still overheats.

Some observations....even when the temp gauge is getting into the hot territory, the radiator still feels cool. I touched the top rad hose (from the engine) and it was very hot which I believe to be normal. The bottom hose (outflow) was room temperature. Now, I know the bottom hose should be coolER than the top hose, but it should still be pretty hot; especially on a car that's currently overheating. Another observation is that the heater in the car NEVER gets even remotely warm.

I suspect one of two things is going on. 1) The radiator is clogged or there's an obstruction somewhere or 2) The water pump just isn't moving coolant around well.

Does any of this sound familiar to some of you? Any ideas? Thanks in advance.
Sounds like the water pump. Also do not run no thermostat. If you want it ice cold. Take a thermostat and take the spring and plunger out. Then put the flat ring in. But I would just run a good thermostat.
 

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Discussion Starter #5
Sounds like the water pump. Also do not run no thermostat. If you want it ice cold. Take a thermostat and take the spring and plunger out. Then put the flat ring in. But I would just run a good thermostat.
Like I said in the original post, we installed a thermostat so we are good there.
well at 180k, it's time to do the water pump anyway. I'd do that and the radiator. Also, welcome back.
I've been hitting up youtube and it appears that to do the waterpump the MFing crank pulley has to come off...is that correct? Looks extremely involved... The radiator, on the other hand, looks stupid easy.
 

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A friend had a similar issue & turned out to be the fans wouldn't come on due to a wiring issue. Have you checked if the fans are working fine ?
 

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Do not make the mistake of buying a chinese cheap pump. Since so much have to be involved just to get to it, I would just buy a well branded one or atleast japan made. I bought a NPW pump for mines
133928
 

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A friend had a similar issue & turned out to be the fans wouldn't come on due to a wiring issue. Have you checked if the fans are working fine ?
Good question. I should have cleared that up in the OP...interestingly enough, his fans are ALWAYS on. Even when you cold start the car. Person who had it before him really did some shady stuff I think.

Are the water pumps on these cars common failure points? What are the fins of the impeller made out of? Are the metal or plastic?
 

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Are the water pumps on these cars common failure points? What are the fins of the impeller made out of? Are the metal or plastic?
Not common failure that i have heard, but then most people swap them out when the timing belt is changed. Pretty sure its a steel impeller with aluminium housing, might pull apart to check out the one i just removed from the car when i get some time spare.
 

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Good question. I should have cleared that up in the OP...interestingly enough, his fans are ALWAYS on. Even when you cold start the car. Person who had it before him really did some shady stuff I think.

Are the water pumps on these cars common failure points? What are the fins of the impeller made out of? Are the metal or plastic?
The factory water pump impeller is metal. Mines was still working perfectly fine when I did the belt job at 170k miles.
133938
133939
 

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So from what I gather, as long as the damn thing isn't totally locked up or leaking...it should work fine. My money is on the rad being really clogged up or something.
 

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So from what I gather, as long as the damn thing isn't totally locked up or leaking...it should work fine. My money is on the rad being really clogged up or something.
Quick way to tell is to run some water from the top of the radiator with the top and bottom hoses out.
 
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