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Hi, I'm new to the forums and need help. I am borrowing my dad's 86 mr2 and it has an overheating problem. Here are the symptoms: When I drive on the freeway, it starts to overheat when I hit the accelerater. Like when I'm going 65 and decide to pass someone up, the temp gauge reaches towards the red area (but doesnt hit red). But as soon as I let off the accerater and the car slows back down to 60ish, the temp would be fine. The next problem is when i'm at a stop light, the gauge will gradually get towards the red. As soon as I start moving, the temp would go back down to normal. This stopping at the light business happens every single time. So when I park, I pop the hood to look at the engine and see that the small fan on the passenger side is not moving..? So I turn off the car and inspect the radiator resevoir thing to check the fluid. The fluid is up to the top! I know this cant be good but I know this isnt the main problem. I didnt check the front radiator fans, but I dont think those are on either (I will check later tonight to see if those are running or not). The last symptom I notice is that, when I turn on the heater to let out the hot air, it doesnt blow ANY hot air whatsoever (maybe this is the key to the problem?). Does anyone know what the problem is, and can anyone guide me to fix this?
 

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I love Cin
91 Turbo MR2
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Not sure where it is on the '86.
But basically there will be some sort of junture in the coolant lines coming from the front of the car to the engine.
It will most likely be very close to the engine area.

You will just have to open up that housing/juncture and pull out the old one and drop in the new one.

... all while watching the coolant go everywhere lol
 

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Dragging up an old thread...

My 86 does the EXACT same thing, but I had a new thermostat put in and it didn't fix it.:sosad: Mine goes one step further to where when it is running hot it will actually cool down to half way if I make a sharp right turn (no, I'm not kidding). I figured that the shop who installed the thermostat knew what they were doing, but after reading about the special coolant refill crap, I'm wondering if they filled it incorrectly (didn't bleed it right). Is there a way to tell if it was bled properly or do I need to go through the whole procedure myself?
 

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1991 Toyota MR2
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My 87 did this, we tried everything and nothing worked. I don't know how to fix it. My motor went anyway so when we put a new one in we had no problems. :\


And wow, its Jeff. :p
 

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Yeah, when they overheat, they overheat the whole 9 yards. Air in the system is a total no-no, so you gotta check thermostat (it's on the engine, next to the dipstick) and you gotta bleed bleed bleed til you're bled dry. Then bleed some more. Worst case scenario is cracked cylinder head, but these mothers need some special bleed process and it needs to be done right.
 

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before you get into thinking its the head check these following things. and the problem could be either or both. you were on to something when you talked about the heat not working in the car. this usually means that the lines going to or from the heater core is clogged. this will happen when people do not flush their entire cooling system. (most people just do the radiator) so if you want to do this its on you but it is a slightly time consuming process. check the heater core lines, heater core, and now the other sloution could very well be you need a new water pump. sounds like the blades inside are worn think about it. at idle you will sit there pump is not moving very fast. you start to overheat. when you are driving you are in mid-rpm range spinning the pump faster and with the combined air flow going to the radiator your temp is fine. you go to pass a car at 60mph + well i have an 85 and i know that at 60mph your sitting at about 3krpms in 5th gear. so you go to pass said car and now you find yourself at lets say 5krpms. the blades inside the water pump just may not be able to handle that demand for the increased flow and pressure. it definatly is not the radiator fans up front. if it were then you would always overheat. ok well i hope i helped good luck
 

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A bit more info on it...

I tried bleeding the system and thought I had it fixed but it didn't help. I filled the line with coolant with the radiator petcock open. When I did this I also had it running and the heat turned on. I didn't have a hose hooked up to the outlet from the petcock...mainly because I didn't have on handy. When I filled the line, coolant pourd out from the radiator petcock outlet. To me that means it has an unobstructed run from the back where the engine is all the way up to the raditor, right? When I undid the petcock I DID get some air hiss before the coolant started coming out...so there probly WAS air in the line. What I'm trying to figure out now is why didn't it fix it.

I'm really bummed out that it might be the water pump cause it's no easy fix..not for me anyway. And very $$$....something I don't have much of. Any way if it was the water oump, would'nt I be able to hear a squeaking noise or something coming from the pulley if it was starting to shit the bed?

Gawd I wish there was an easy solution to this...:disappoin

BTW...my heater IS working
 

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for brian . sorry but it looks like to are going to have to replace lines. that gunk that is clogging it up has turned acidic now. very bad for engine. if you want to try compressed air or find the line that is clogged and well unclogg it. coat hanger with a rag on it would work if you dont have the money right now
 

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Hey guys, I'm a kinda expert on this thang now! Had overheating for about a month and changed thermsotat etc. Wanna say some important things here, cos I've been there, okay? Hopefully all sorted now, but some of this is CRITICAL if you get overheating!

1. Change the therm. Can't do any harm
2. BLEED PROPERLY. I take up to an hour bleeding, and it's a critical process. Don't rush it and don't think it's done until you've done it again! I'll go into detail below!
3. If your heater isn't working well, it's a sure sign on the MR2 that it hasn't been bled properly, or there's air in the system.

Now, bleeding goes something like this:

Car on level ground. Put the heater control on the HOT position. Fill the coolant to the top of the filler. Attach clear bleed hoses to the front heater bleed point and the radiator bleed point. Attach the other end of hoses to the hood, so they're wayyyyyy above the height of the engine. Open each bleed valve (two remember) at LEAST 3 TURNS. You'll see the coolant creep up the hoses, but don't take any notice of this at present. What you're looking for is coolant creeping up BOTH hoses, equally, ALMOST TO THE TOP and STAYING THERE, without falling back, and without air bubbles rising...

Put the cap back on the filler and half turn it to it's first position. Start the engine and run at fast idle (3000 rpm) for tow minutes. You can see the hoses from the driver seat and will see the coolant rise and fall as you work the accelerator pedal. After two minutes, switch off and refill the filler to the top. Replace the cap again and run at fast idle for another two minutes. Repeat this for about an hour (which is what I did) until the coolant gets to almost the top of the hoses and stays there without falling back. It takes some work, and you'll see air bubbles in the tubes. You don't want air bubbles, so this is an important process. Once the coolant rises in the tubes, stays there without receding, and no further air bubbles are rising, you SHOULD be okay. Also, while sitting in the car, you should be able to hear the system burbling and bubbling, as air is forced through the system and out.

It also helps at some stage during this, if you raise the back of the car, so the hood points slightly downwards. This helps the liquid get from the back to the front.

Once all is okay, you can tighten the filler cap fully and the bleed valves, remove the tubes and run the car for 10 minutes or so, to check the level in the filler doesn't fall.

One noticeable sign that the car is bled properly is the fact the radiator gets VERY hot throughout its mass. The radiator fan should cut in somewhere along the way, and the fan will ONLY work when the radiator gets hot. So if your fan doesn't cut in (and it should) the radiator isn't bled properly or is blocked otherwise. The Stainless pipes (two) that run into and out of the radiator should also be VERY hot - another sign it's bled properly. Your heater should be throwing out hot air too when the engine is running - yet another sign.

The main point here is the bleed tubes and the height of the coolant in the tubes. It needs to stabilize right up towards the top of the tubes and no air bubbles. This is the best pointer I can give - and I spend an hour doing this process, as I say. Don't cut corners, but some people will bleed it quicker - if they rev the car more, for example.

As I say, critical critical process, and most MR2's will overheat if not bled properly. Hope this helps, guys, but let me know if I can help further. Good luck
 

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thats alot to read... so imma just throw ideas out there and if you done them then ignore it.
way i would do it... in this order.

thermostat

fan motor operation... does it work... check for an obstruction in front of the radiator.... bags, dead animals... anything

coolant change / flush... manual flush using the water pump and not a machine so you can tell the working order of the pump

quick head gasket test.... run car and check for bubbles in the coolant... or white smoke from the exhaust
 

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ahhhh crap....when I take the cap off my coolant line, I CAN see some..well...actually alot of foamy, but not discolored bubbles in the coolant itsself:argh:

shit...well thanks everyone for all your help and suggestions. I guess I'm in short order to either get a new engine or replacing the head gaskets.

CRAP!
 

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brianj said:
ahhhh crap....when I take the cap off my coolant line, I CAN see some..well...actually alot of foamy, but not discolored bubbles in the coolant itsself:argh:

shit...well thanks everyone for all your help and suggestions. I guess I'm in short order to either get a new engine or replacing the head gaskets.

CRAP!
Bleed it religiously first, until you're exhausted! Worth a try, as heads are not the easiest (cheapest) things to deal with, and I'd check the FREE stuff first, like bleeding!
 

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tHa kNiGHt FaLL said:
well to replace the head gasket would cost you 100.00 if you do the work compared to a rebuild that would cost a thousand or more. couldn't hurt to try it
I wouldn't touch the head until I was happy with the bleeding process.
 

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Man it is nice actually to tell what u need to do in full description as to where alot of people need that much information...... unfortunately it would appear that our boy here is in deeper trouble than the story led to :0(
Sorry man, but it may be early enough to not need engine work.... if my assumption is correct.
 

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Zz_005_zZ said:
Man it is nice actually to tell what u need to do in full description as to where alot of people need that much information...... unfortunately it would appear that our boy here is in deeper trouble than the story led to :0(
Sorry man, but it may be early enough to not need engine work.... if my assumption is correct.
Sorry for too much info, but bleeding is critical, I can't stress that enough. If one air bubble gets in, you're in trouble and the car will overheat, sometimes after 100km or so of normal running. Toyota dealers have told me that many cases of suspected engine trouble have not been engine at all, but been down to the bleeding not having been done properly. It's worth doing, because it's free!
 
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