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Hello all!

 

I have a problem that I am hoping some of you can give me some insight on. Also I hope this is in the correct forum, I wasn't sure if it was supposed to be the powertrain or the general.. Anywho...

 

I have a 1993 Grand Prix 3.1, and today it decided to increase pressure in the coolant system, and caused a small leak in the upper radiator hose, and the metal coolant rail from the water pump to (not sure where). We pulled up, I opened the hood and found them spraying bad and causing smoke. I understand that I will have to replace both, but my question is this, why did they BOTH go at the same time? I think I have it narrowed down to a plugged radiator or a bad water pump (though I could be completely wrong.

 

Anywho, let the engine cool after finding the leak, I replaced the thermostat really quick and topped off the coolant, and turned it over. I opened the upper radiator hose air valve and nothing came out. Waited, revved the engine, nothing came out. So I squeezed the hose, held it, and closed the air release in hopes to help. Re-opened, again nothing happened. Opened the radiator cap while running (yes I know I am incredibly stupid for doing this), and it looked low, so I added coolant, took a few drops (almost literally) and closed it up. Waited, still nothing from the air release in the upper hose. Tried squeezing upper and lower hoses, and nothing happened, didn't look like the water even moved, can normally see it in the coolant reservoir and hose, but nothing this time. I ended up turning the car off and calling it some colorful names before I gave up and went inside.

 

Before this I had the issue of it randomly overheating, one day it would be fine idling, or sitting in a drive-thru, the next day it would begin to overheat in a drive-thru. I replaced both relays for the dual cooling fans thinking that was a good place to start. Didn't help, I picked up the thermostat to try, and then all of this happened. It is worth noting the temperature never got over 240 degrees (according to the gauge cluster anyway), and usually runs about 200 or less even under high load.

 

I am so lost at this point, the only thing I could think of was a clogged radiator which would stop coolant from moving, or a bad water pump which didn't move the water. I'm fairly desperate too since my Wife starts a new job Tuesday and this is our only vehicle. Tomorrow I think the plan is a new water pump ($20) to see if that works, and the new upper radiator hose (unless you guys say differently) I cannot find a parts store that has the metal line, and no one knows what it is called either. If you know the part I would appreciate the name, but would rather have figuring out the pressure issue first..

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1.  The metal tube almost certainly rusted through due to lack of cooling system maintenance.  Best guess is that the metal tube is part of the heater hose assembly, but I haven't spent enough time looking at a 3.1 to know for sure.

 

2.  The rad hose almost certainly began to leak because it's old as the hills, perhaps even original.  Again, another sign of cooling system neglect.

 

3.  It is possible that you've over-pressurized the cooling system due to overheating or a combustion-gas leakage into the cooling system.  The radiator cap SHOULD have relieved the excess pressure--but sometimes they get plugged and cannot release pressure.

 

4.  If this were in MY driveway, I'd be looking at:

a.  Signs that the coolant is degraded.  This is most-easily done with coolant test-strips that check both the freeze protection and the acid level of the coolant.  The test strips don't work with some long-life coolants, but if you "had" the plain ol' green stuff, they should work just fine.  I've seen "green" coolant so degraded it looked like black coffee.

b.  All the coolant hoses including the two for the heater system.  If they're ancient, you'd do well to replace them all at once. 

c.  Signs that the radiator cap is defective.  Once the hoses and cap are verified good, you can pressurize the cooling system looking for other leaks.

d.  Signs of combustion gasses in the cooling system.  If there's combustion gas in the cooling system, you're looking for a head gasket or a cracked casting.

e.  Signs of coolant in the oil.  If the vehicle is allowed to sit for a few hours, the oil will float on top of the coolant.  Pulling the oil pan drain plug will result in coolant coming out the drain, followed by contaminated oil.  If the engine has recently run, the oil may look like a "milkshake".

f.  Signs that the radiator overflow tank is contaminated with oil or degraded anti-freeze.  They can often be cleaned by removing them from the vehicle, filling them 1/3 full of hot, soapy water and a couple of cups of sand.  Then shake vigorously so the sand and soapy water can scour the inside of the tank.

g.  Buy a "flush and fill" kit so that the cooling system can be flushed with a garden hose.  DO NOT FORGET to drain the flush water by removing the radiator draincock and the engine block drain plug(s).

h.  Buy FULL STRENGTH anti freeze and a gallon of distilled water.  Buying "50/50 premixed" antifreeze is a consumer rip-off, as the half-strength stuff costs nearly the same as the full strength stuff, and a gallon of distilled water is about a dollar.

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I checked all the hoses, looks like the one rubber seems to be the only one in bad shape. I replaced the thermostat, radiator cap, and hose and now seems fine. The only thing is when it is revved up the temperature drops which I never noticed before. Idling maybe 10 - 20 degrees but driving 30-40 degrees drop. Is this normal?

 

Edit: sitting in the car while running, I had the heat in and it stayed at 200, the heat completely off it is now at 220...

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I checked all the hoses, looks like the one rubber seems to be the only one in bad shape. I replaced the thermostat, radiator cap, and hose and now seems fine. The only thing is when it is revved up the temperature drops which I never noticed before. Idling maybe 10 - 20 degrees but driving 30-40 degrees drop. Is this normal?

 

Edit: sitting in the car while running, I had the heat in and it stayed at 200, the heat completely off it is now at 220...

Just sitting those numbers look fine. One of the fans will come on at 226ish? Cruising while ambient temp is below 70 you should not see 220. The drops are just a slightly sluggish thermostat. Probably just a characteristic of your new one. It will be more and more obvious as it gets colder. If it is not affecting your cabin heat then I wouldn't worry about it.

 

What did you do about the metal line leak? Were you able to bleed the air from the system?

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I was unable to find a new metal line, and for it doesn't appear to be leaking now... But will still look to get it replaced.

 

I checked the fans when it got to about 230 after turning the heat off and neither was running. I've got new relays I have been putting in and trying but with both new relays it doesn't come on. Took fan relay two out, and AC relay out and one kicked in, cooling it down to 200. I put them back in and did the same thing, got hot and no fans running. Only got the left side fan to work too.

 

The one fan is now working, but not the right sides one. Only runs with fan relay two unplugged. And lastly yes I was able to bleed the air out.

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There's a way you can test the fans and relays with less parts swapping.  Short the A&B pins of the ALDL and the fans should come on when you turn on the ignition.

http://www.pontiacperformance.net/TechArticles/images/Fiero_Schematics/Fiero_ALDL.png

They should both spin up briefly.

If they do, the problem is not the fans, relays, or ECM, but possibly the engine coolant temperature sensor (a different sensor than the one that controls the temperature gauge in the dash).

It's also possible if all indications are it's the sensor, that the sensor itself might not be bad and there's actually an air pocket around the sensor.  Either from incomplete bleeding or combustion gasses.

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The two fan circuits are separate past the ECU, so I have a feeling that the act of removing one of the relays might be a coincidence. So, at this point, is the idling temp the only issue? No more leaks?

 

Long term idling temps are obviously fan dependent:

-I would start by testing those fans directly by jumping pins 30 and 87 on their relays. Paperclips work well for this. Simply make sure each one turns on. You do not need to test for longer than a couple of seconds. If they both run, then you know their control circuit(s) are the culprit(s).

-You said the one fan does not run while the other's relay is in place. Let's test that theory: Make one come on however you did before, then place the other's relay back in before reaching 200. If this does not turn it off, then they are indeed independent (which is the likely result, unless someone really mangled the wiring before).

-Assuming these tests pass, then you can start worrying about the coolant temp sensor(CTS)/wiring. There are many threads here that talk about that, so I would browse those.

 

To keep in mind: In normal operation, first fan kicks on at one temp, the other kicks on if the temp keeps climbing. Also, CTS's are separate for the ECU and for the gauge. Either sensor could be reporting a false value.

 

Edit: Looks like Shawn beat me to some of it. Nice work.

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Here shortly I will go jump and see if both fans work with that also connector..

 

However, now there's a new issue. It was doing fine after the hose, radiator cap, and thermostat replacement until today when it got hot, and showed a service engine light. The drivers fan turned on, cooled the engine off and I turned the car off. I turned the car back over and the light is no longer on. Unfortunately I don't have a original obd reader, and the local parts store doesn't either... Any thoughts/ideas?

 

 

Sent from my iPhone using Tapatalk

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Here shortly I will go jump and see if both fans work with that also connector..

 

However, now there's a new issue. It was doing fine after the hose, radiator cap, and thermostat replacement until today when it got hot, and showed a service engine light. The drivers fan turned on, cooled the engine off and I turned the car off. I turned the car back over and the light is no longer on. Unfortunately I don't have a original obd reader, and the local parts store doesn't either... Any thoughts/ideas?

 

 

Sent from my iPhone using Tapatalk

You have an obd1 so you can get codes by counting SES light blinks with A and B terminals shorted.

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You have an obd1 so you can get codes by counting SES light blinks with A and B terminals shorted.

 

The engine code was my own fault, and want to kick my own butt right now. I took out the air box when putting in the new upper radiator hose and left the sensor to the box disconnected... I'm an idiot.

 

I'm still having the issue of it getting to the point where that 227? degree fan kicks in and has to cool it down when idling. Something seems wrong to me with the cooling system itself besides the fan that isn't working, but for the life of me I can't find it/figure it out... I will be testing the fans today, since it was heavily snowing here yesterday...

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A number of GM vehicles have crazy - temperatures like that, 224 + 226 + pretty common. if you need to drive the car right now perhaps you should just bypass the primary cooling fan relay until you can figure out what it's doing.if you can get to the underside of the electrical center you can ground the green wire that goes to the relay and it should only come on when ignition power. the fan will run all the time that the key is on and you'll likely throw a code for the cooling fan relay but since you're down to one car you would be able to drive and get where you need to go until you can fix it properly

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Imp558,

Thank you for the heads up! I definitely might try that now, I got a grand am that's leaking fuel, and this Grand Prix that has cooling issues. With snow on the ground and no garage it's easier to work in the cooling issue...

 

A BIG thank you to everyone who has posted and has helped me with all this.

 

 

Sent from my iPhone using Tapatalk

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it's easy enough to find tables for the coolant temperature sensor telling what the resistance should be at different temperatures. With that in mind all one needs is an ohmmeter to tell if the coolant temp sensor is any good. The reality is if you're going to drain the cooling system down anyway the coolant temp sensor is cheap like $15 and can cost you a lot of fuel economy if it isn't reading correctly. same thing with the intake air temperature sensor

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I'm guessing you are referring to the metal tube that goes from the waterpump housing down the framerail and towards the firewall? 

 

Not sure what would get someone else to suggest it rusted out because of "poor cooling system maintenance" Its a low hanging metal coolant line and you live in Michigan. Its not rocket science as to why it rusted out. the usual fix is to just cut it back till you find good metal and clamp a piece of heater hose on it. 

 

The radiator hose, it is 23 years or so old now, not exactly surprising why it has worn out. 

 

I'd replace both hoses if you haven't done so already. Fair warning these cars can be a HUGE pain to bleed the cooling systems on. If youv'e been driving on it just go out in the morning before you go anywhere and check the coolant level and add to it. 

 

Are you getting proper cooling system pressure?

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I'm guessing you are referring to the metal tube that goes from the waterpump housing down the framerail and towards the firewall? 

 

Not sure what would get someone else to suggest it rusted out because of "poor cooling system maintenance" Its a low hanging metal coolant line and you live in Michigan. Its not rocket science as to why it rusted out. the usual fix is to just cut it back till you find good metal and clamp a piece of heater hose on it. 

 

The radiator hose, it is 23 years or so old now, not exactly surprising why it has worn out. 

 

I'd replace both hoses if you haven't done so already. Fair warning these cars can be a HUGE pain to bleed the cooling systems on. If youv'e been driving on it just go out in the morning before you go anywhere and check the coolant level and add to it. 

 

Are you getting proper cooling system pressure?

 

It does come off the housing but doesn't go to the firewall, I traced it finally and mine only goes to the engine under the throttle body, connects to a rubber hose and goes under the valve cover so i lose it.  There's very, very little rust on it, and looks like it found a weak spot and created a pinhole leak. It ended up being a faulty radiator cap, the copper had corroded enough and wouldn't allow the pressure to escape.

 

As for pressure I have no idea. I'm not sure how to pressure test it per say, and not sure I would have the tools to do it either. Mainly no compressor to put any pressure into the system. I have been keeping a close eye on the coolant and have been good ever since.

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