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Discussion Starter #1 (Edited)
For whatever reason my car overheats when i am at higher speeds. If i stay constant at 70 or 80 it wont overheat... even if i ride out a high rpm.

It tends to overheat when i am accelerating and changing lanes... Like accelerating from 70-80 multipe times.

The temp wont go back down until i slow down... and it doesnt drop immediatly... it is a more slow decent.

Temp gauge hasnt gone past 75%

Now here is what makes it wierd(IMHO)...

1. I changed the thermostat(bought from toyota... tested before replacing)
2. All the coolant lines are fine
3. I replaced the radiator... with a used one but it was clean
4. Im not losing any coolant
5. my car passed a block test... Numerous tests... ranging from dead cold engine to full operating temp.
6. headgasket was done not even 4000 miles ago

Any other suggestions as to what it could be? Seems like it's been overheating ever since i replaced the heater control valve about a month ago.

I REALLY dont want to bring this car to a mechanic but i am starting to run out of ideas... and money...

EDIT: Just to add in some additional info... I one of the things on my HCV snapped causing the hose to pop off and spray coolant everywhere... Maybe i cracked the head?

Also my current water to coolant mix is like 15% water and 85% coolant.
 

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hehe coupla things:
More water, less coolant
Check that rad cap - just replaced mine. The rubber gasket on the bottom caused the thing to overpressure and keep the thermostat closed. Wiggled it and air came rushing out followed by car running normal again.
 

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"Also my current water to coolant mix is like 15% water and 85% coolant."

Add more water... all 'coolant (i.e, ethylene/propylene glycol' does is increase the boiling point of water and decrease the freezing point. It doesn't have the heat retention properties that water does, so more is not better.

50/50 is the highest coolant to water percentage you should go...
 
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hmmm i think i'll do the same because i am having similar problems like cramerizking
 

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one thing u forgot to due after changing all those things
u need to burp the car.
jack up the front as high as u can get and let the car idle for 5 min.
then give it some gas hold to 2000rpm for few min.
u should see air bubble coming out.
remember to refill the rad. after this, coolant will be spilling out.
 

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Discussion Starter #8
Friend of mine suggested that it might be the thermostat senor... But if it was i wouldnt get such consistant readings right?

Prob gonna water down the coolant tomorrow and can clutch depending on whether or not anyone stocks it.

Just wanted to BUMP and see what you all thought about my friends idea...
 

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i had the same problem on my rx-7 I had put a supra front mount on and it would cause me to over heat around 70 80 mph but i could run 60 all day with out a problem
so check to make sure that you dont have something blocking the air flow
 

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When burping are you seeing air bubbles? If so you have air pockets which means a leak somewhere like the headgasket or maybe the valve you replaced.

Cap is a good place to start. I have seen some 7Ms overheat from chewed up/rusted out water pump inpellers from bad coolant.
 
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Re check your radiator my friend. YOumay have had a radiator replaced, but if you did not flush the negine with radiator flush ( only the cooling system) , that rust can go right back and clog the radiator tubes inside the radiator.

It happened to me on a brand new radaitor. I actually took a flash light and shown it into radiator..and saw the blockage fisrt hand....now my car runs like a champ. No overheating on long drives, or while boosting, or while going up hills....

THis is also one of the suggestions. I used Prestone radaitor flush a couple of times to make sure everything was drained.

I also drained coolant at the engine block and back flushed with high pressure hose...
 

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dude my car did same shit what it was on mine was the heater core I filled the rad but didnt try the heat is your heat working if not then you have to bleed the system of air and add fluid till heat begins coming out. ten bucks says thats what it is.
 

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Discussion Starter #14
Well i havent had the chance to test it out again as the weather has been shitty. But i ran a hose through my rad and the "new" rad a bought... Didnt noticed any difference in flow between the two. Plus i was pretty suprised at how clean mine looked. I'm going to do the fan clutch at my next available oppertunity... I already changed the coolant/water mix.

My fan clutch IS bad so even if that isnt the problem it's just preventative maintenence i guess.

So we shall see. Also yeah my heat works. I burp the system every time i screw with anything involing the removal of coolant hoses and so on.

Thanks for all the suggestions so far... I'll update again when i get a chance to beat on her some more.
 

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does your heat work when your beating on it tho. Try turning the heat on full well you are beating on it and check to see if the heat stays on. Because this sounds very like what my car did to me. Maybe im just out to lunch on this tho :dunno:
 
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Take compressed air and clean out the A/C condensor and intercooler of debris in the fins if you haven't already. Also if you think your rad. is plugged fill it with CLR and let it sit, will be like brand new when done. Also a little trick when it comes to burping is to take a piece of rubber hose, I use a 4X4 truck shock cover that fits over the radiator fill cap that seals up. It about 16in. tall and I keep it full of coolent when burping. This in effect raises the high point way above the heater core and speeds burping up about 10x that of just parking on an incline. After doing this I realized I never completely burped the car before, even on a hill its close to impossible.
 

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Was having similar problems. After changing the thermostat (I use a 160o), I still was having some odd fluctuations. I checked the two sensors on the thermostat housing and the lower one with the larger clip had a bad wire (it looked fine, it even held together on its own). It was ate away by oil and grime. I got some new wire and soldered it up and covered. Good as new. No more fluctuations. Running beautifully. Good luck. If you have a bad fan clutch tho, its probably that. If the new fan doesnt work, check those wires into the thermo housing.
 

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p.s. red line water weter is not a bad idea to put in.


bcastine good idea ill remember that one and blow out the radiator also.

i had a bunch of crap between the radiator and condenser including a empty pack of cigarets
 

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I put in Lucas Oil water wetter and it brought the temp down.. I go for runs out in the desert when its 110 degres out and the car runs at 1/2 on the gauge. No matter if I'm running 50mph or 90-100 mph (short bursts)
 

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Discussion Starter #20
ok i changed the fan clutch today and the car doesnt seem to be overheating anymore... but... now the car maintains a higher temperature than normal. ???

Where-as before this crap the gauge would stick at about 45% now i would say it sticks at about 55-60%

I also added more water to the coolant/water mix... i would say now that im just around 50%

You think the water wetter stuff would bring it down a little more?
 
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