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Discussion Starter · #1 ·
I have a 91 Supra turbo that only has 60K on it. I bought the car in 2012 with only 48K on it. It had been sitting in a barn down by San Diego for 10 years. The guy bought it in Florida and drove it back to California and then pretty much parked it. Apparently he traveled a lot and just never got back to it.
When I got it I was concerned about things like seals, fluids etc. so, I went over the car and replaced anything that was cracked and or brittle which wasn’t much. I did change all the fluids and started driving it. It ran good for a long time and even when I discovered the bad head gasket it was still running strong. I replaced the head gasket and new ARP head bolts and torqued it to the correct setting. The car has been running great except for when I drive it down off the mountain where I live. I live up at 6000 feet and the car runs fine up here and usually runs fine when I have gone up and down the mountain. The problem which has happened at least three times, is when I drive it down to the city on hot days. I mean like 85-90 degrees plus. It really occurs when I start coming back up the mountain and I get up to around 4500-5000 feet. It starts bucking and missing and is running so rough that it wants to stall or shut off. On one occasion I was able to keep it going by pumping the throttle. It kept running rough but did smooth out. On another occasion it just shut off while climbing but, I was able to throw it in neutral and start it again and then get to a turn out. The temperature gauge was showing hotter than it ever gets but I was able to start it and it ran smooth and got home with no problem.
At this point I don’t really trust the car to get me up and down the mountain on really hot days. I don’t have the A/C when this happened either. At this point I don’t know what I should be looking for.
My first thought is cooling system, radiator flow restrictions? Electric fan relays, or something in the ignition that is getting too hot in these high temperatures.
Other than that the car is the most dependable car I own.
Any suggestions or help would be appreciated, thanks
 

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Look for evidence of someone that previously may have poured some coolant stop leak into the radiator. (Does not do what it advertises, though it cloggs the coolant system real nice)
Could possibly something simple as a clogged radiator.
Though you should have noticed some shitty looking coolant when you replaced fluids, as well as the coolant passages in the head and block when you did the HG.

Make sure your fan/shroud/ fan clutch are all working properly and not broken.

You say you have electric fans?
If that's the case, it's probably due to lack of proper airflow across the radiator.
They are pretty notorious for not meeting coolant requirements when pushing the vehicle hard.

Swap back to the stock fan driven from the belt, it moves way more air.

Also do you still have the full engine under tray? (Huge plastic tray underneath)
 

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Driving up a mountain in hot weather is about as much stress as you can put on the car and lack of air flow at low speeds is probably killing you. I would verify all the fans are working. Then as said above 30 year old radiators can be clogged or junked up. I would lean towards that especially since the car sat for 10 years and you have no idea how it was taken care of previously.
 

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Discussion Starter · #4 ·
Yeah, I tend to agree about the stress created going from 85-100 ambient temperature at sea level to around 80 degrees when going up in elevation to 6000 feet from sea level. The other thing is the air gets much thinner at elevation which might affect the air flow.
The electric radiator fans I was referring to are the ones that come on when the car goes from running hard and will continue to run until the engine cools down some. I bought a Greddy turbo timer that will keep the car and fans running to continue to cool down the turbo after the car is turned off. I have been letting the car run for at least a minute or two before turning it off to continue to let the turbo cool off some before turning the car off completely. I think that I have the wiring figured out that I need to tap into on the ECU but, not completely sure. I have also seen where some guys just connect to the 12V wire on the back of ignition key switch. So, if anyone has an answer for what works best, I would appreciate that also.
Ok, back to the radiator. When I changed the fluids in the car back in 2012, I don’t think that I completely drained the cooling system because it looked like it had fairly fresh coolant in it. So, that didn’t get done at the time but, a few months later we did the head gasket. I’m pretty sure that nothing was done to the radiator at that time. So even though it might have been emptied it was definitely not flushed. I have been thinking about getting a new aluminum radiator to replace the stock one but, I have an automatic and all the new radiators don’t have any bungs for trans cooler lines. Now that I think about it, I’m not even sure that there are any cooler lines running to the radiator. I’m going to have to look this morning and see if they run to a factory trans cooler or to the radiator. Having said all that, does anyone have any recommendations on which aftermarket radiator is a good replacement?
I’m going to have to go take a better look at the radiator this morning but, I think a lot of my problem is in cooling system and I’m getting a sense from you guys that you’re in agreement. Given that the car is 30 years old and has had no cooling system work done on it in the nine years that I have owned it, I think that it’s a good place to start. I’m going to have to get out the service manual and test the fan relays while I’m at it. In the event that the trans cooler lines connect to the radiator should I take the time to have the bungs soldered on the radiator or get a separate trans cooler instead. I know what I’m thinking but, I’m interested in what you guys think. Thanks
 

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The mechanical fan moves thousands of cubic feet per minute. The electric only a couple hundred.

The reality is that an inline engine like this the back cylinders will always run hotter. So while the electric fan might be cooling the coolant it might not be enough to get some airflow to the back of the engine. It doesnt mean you have to go back to the mechanical fan but you may end up needing a pusher and puller set up. Maybe even one running 24/7.

I agree with everyone else up hill in really hot weather is about as hard as it gets on an engine. Only thing that would make it worse would be towing. Not knowing the cars history you need to go over the whole cooling system in depth.

The radiator and coolant condition is a good place to start. Also look around at the cooling fan set up. Ive installed these on other cars before and the ones I used had an adjustable thermostat. Might be able to crank it down say come on at 180 or 190 instead 210 (example of course).
 

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You should drain your coolant immediately and inspect it for any presence of stop-leak. If it checks out, you can easily pour it back into the radiator and re-burp the cooling system.

Koyo, Megan Racing, and Mishimoto all offer aluminum radiators that are good upgrades over an old school plastic-end-tank radiator. That plus a simple trans cooler is very easy to install and it should make a fantastic difference in cooling.
Adding a trans cooler circuit to an aluminum radiator is a pain in the ass and not worth it. Just set up a dedicated trans cooler, it's very easy.

If you really need the cheapest/easy button fix, a few aftermarket companies have made AT compatible OEM style plastic tank radiators and those have been sold through RockAuto, Ebay, Autozone, etc, and while they work they're an OE replacement and not an upgrade of any kind. I've also been unimpressed by the thread-on hose fittings for the AT cooler loop on more than one of these kinds of radiators, in that they're very easy to strip and finicky about sealing well. If you choose to go this route, I'd strongly recommend buying from a local shop like Autozone that can take a warranty return if something like that happens.

While you have your radiator out, use compressed air from the radiator side to blow out all the small twigs/dirt/etc that get embedded in the front of the A/C condenser. Depending on where and how it was driven, you might have a lot of blocked airflow there as well.
 
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Discussion Starter · #7 ·
Ok, I have three electric fans on the radiator and the regular water pump fan with fan clutch. There’s two small box fans like on your computer running vertically along the left side of the radiator inside the engine compartment and one fairly large round fan about 10”-12” in diameter on the right side of the radiator on the intercooler side.
It also looks like there’s an external trans cooler and possibly a small power steering cooler that are out there also. I think that probably solves the new radiator connection issue.
To the question of the front under tray under the engine pulley area, it looks like mine is missing. Additionally, the fan shroud was damaged and the bottom half is missing. The upper side is held on by a small piece of plumbers tape. I never really paid much attention to it thinking that it was in place of a missing screw on the fan shroud.
It appears that, at the very least I’m going to need a new fan shroud, if I can find one.
I took some pictures of the fans and if I can figure out how to upload pictures I will post them. At this point I’m going to need to clear up some space in the garage and take a few things off and Jack up the front end and get a better look from the bottom and drain the coolant.
 

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Discussion Starter · #8 ·
I just spent some time going through the factory service manual and the three electric fans are all for cooling down the A/C condenser. The radiator is able to be disassembled and with new upper and lower tank gaskets reassembled after cleaning. Good luck getting the parts. The ATM oil cooler is inside the lower radiator tank and is removable to be cleaned but, again you would need the tank gaskets, actually o-ring type gaskets.
So, a new aluminum radiator would also require a separate oil cooler for the transmission. I need to see if I can find a fan shroud for starters which I’m not too hopeful of finding. Probably going to flush the radiator and replace the t-stat in the next couple of days and see what comes out.
 

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Fan shrouds are still availab;e from Toyota last time I checked.
You should confirm your fan clutch is working properly. At a bare minimum from a cold start the fan should be fully engaged and roar then after about 15-30 seconds you should hear the fan noise go away.
 

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Fan shrouds are still availab;e from Toyota last time I checked.
I can confirm this. Got a new one a couple months ago from the dealer. Toyotapartsdeal has them online but with shipping came out the same as my local dealer.

Top one is the main shroud (16701), bottom one is the lower piece (16712). You'll need 2 of the clips to hold them together (16701A).

261047


261048
 

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Discussion Starter · #11 ·
Thanks for the heads up about Toyotapartsdeal. They have the best price of any of the other websites that I have checked. I’m going to order the upper and lower shrouds. My upper is broken and the lower is missing. I’m probably going to need the clips too. Going to flush the radiator today or tomorrow and I will probably make a decision on what to do about that depending on what comes out. I checked all of the companies that sell aluminum radiators and given how much I drive the car, I’m not sure that I want to pay between $300-$450 for a radiator plus $200-$300 for a transmission cooler. I think that a new stock radiator would probably be a option for the money. I guess that my question is, does a new aluminum radiator have more rows and or increased cooling capacity vs the stock radiator? If they do then that might give me something to think about.
I live in California and if I’m not mistaken, I won’t have to get a smog check from now on to register the car. This is year is my off year for the check and 2022 in the normal cycle I would be due for the smog check to register it.
I have been waiting for a while in order to upgrade the turbo, exhaust and possibly the intercooler if the turbo requires an upgrade and any other peripheral parts. I just want to upgrade the HP to 300-350. Nothing too crazy just enough to make it more fun to drive.
So, sorting out the hot weather driving issues and the associated costs along with smogging the car will affect what happens here. I want a street legal car with 75-100 horsepower more. Thoughts?
 

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Stock radiator is fine for that. I have 12 psi and car is fine with A/C on on a hot day stopped in traffic or having fun in the mountains.
 

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If you're missing everything you will probably need to look at part 16701B as well if it's available. It's a little rubber piece that helps seat the shroud to the radiator on the bottom. You'll need the bolts too. Two on top for the main shroud and three for the A/C fans.
 

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Take a peek at the front of your old radiator to make sure it's not plugged up with road dirt, leaves, fuzzy stuff, etc, that can reduce the efficiency of your radiator. Make sure you have the plastic shroud including that little strip (16712) that took me years to find. You could also check your thermostat by removing and putting it in a pan of hot water and raising the temperature gradually. It should be open at 180 °F. The temperature rating usually stamped on it. Removing the radiator, back flushing it, carefully and spraying out the fins could be helpful. Always use distilled water with pure anti-freeze or get a pre-mix 50-50. I use the old school green silica phosphate containing antifreeze since I have a brass and copper radiator. Check for stored diagnostic codes. Your map sensor is getting a workout.



261143
 

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Discussion Starter · #15 ·
Very nice clean engine compartment. I ordered both shrouds, clips and cushions from toyotapartsdeal but, I didn’t think about the bolts. I think that they are probably still on the shroud on the car. It’s just broken on the top right and all the fans are mounted. At this point I’m just ordering and gathering parts and supplies to do the job. I don’t want to get the car out of the garage and start working on it until I have everything. I don’t like to start and stop on a job. I’m probably going to remove the radiator and clean it out off the car. This way I can clean the fins with a fin come on front side of the radiator that is up against the A/C condenser and the back side of the condenser. Does no good to clean the inside of the radiator without addressing the air flow.
On another note, I took one of my other cars in for a smog yesterday and and I asked about the car not needing a smog after 30 years and he said that it doesn’t matter and it’s going to need a smog check. Now I’m wondering if I can get an upgraded CT26 with a 57 trim and still pass smog. The shrouds should probably be here next week so, I will pick this up then. I also need to charge the A/C and trouble shoot a couple other small problems.
 

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The upgraded turbo won't impact passing smog. You will need a functioning catalytic converter, working EGR, and good fuel control. And they will pressure test the tank so make sure the evap lines aren't rotted out. The cutoff is 1975. Anything made after that needs to pass smog in perpetuity. They are supposed to do a visual of the engine, but most of the techs wouldn't know original from modified unless its blatantly advertised.
 

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I have a 91 Supra turbo that only has 60K on it. I bought the car in 2012 with only 48K on it. It had been sitting in a barn down by San Diego for 10 years. The guy bought it in Florida and drove it back to California and then pretty much parked it. Apparently he traveled a lot and just never got back to it.
When I got it I was concerned about things like seals, fluids etc. so, I went over the car and replaced anything that was cracked and or brittle which wasn’t much. I did change all the fluids and started driving it. It ran good for a long time and even when I discovered the bad head gasket it was still running strong. I replaced the head gasket and new ARP head bolts and torqued it to the correct setting. The car has been running great except for when I drive it down off the mountain where I live. I live up at 6000 feet and the car runs fine up here and usually runs fine when I have gone up and down the mountain. The problem which has happened at least three times, is when I drive it down to the city on hot days. I mean like 85-90 degrees plus. It really occurs when I start coming back up the mountain and I get up to around 4500-5000 feet. It starts bucking and missing and is running so rough that it wants to stall or shut off. On one occasion I was able to keep it going by pumping the throttle. It kept running rough but did smooth out. On another occasion it just shut off while climbing but, I was able to throw it in neutral and start it again and then get to a turn out. The temperature gauge was showing hotter than it ever gets but I was able to start it and it ran smooth and got home with no problem.
At this point I don’t really trust the car to get me up and down the mountain on really hot days. I don’t have the A/C when this happened either. At this point I don’t know what I should be looking for.
My first thought is cooling system, radiator flow restrictions? Electric fan relays, or something in the ignition that is getting too hot in these high temperatures.
Other than that the car is the most dependable car I own.
Any suggestions or help would be appreciated, thanks
Clean intercooler and go with a bigger all aluminum radiator
 

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If you're unable to find the weather stripping for the shroud from Toyota, you might check out home improvement stores. I know Home Depot sells all sorts of seals for things like garage doors, as well as for A/C ducting. Could possibly also use some sort of edge trim molding, or thin window seal from a body or glass shop.

Sometimes you have to get creative. :)
 

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Discussion Starter · #19 ·
Thanks for the info on the turbo and smog. That has been more of a want than a need but, at least I know what I can do when and if the opportunity arises. I know that when you start upgrading it becomes kinda like Pandora’s box; one thing leads to another!
I just got a notice that the shrouds have shipped so, I’m just waiting on them for now. I also got the service kit for the K&N air filter and some degreaser to clean up when I get the radiator and shroud off. Might as well clean it up while it’s off. I also ordered some R134 to recharge the A/C. I’m going to just turn this into my summer service on the car. W
When I get it out of the garage and start working on it I’ll take a couple of pictures to show you what I’m working with.
 
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