Well, so far, this isn't one of those mystery overheating scenarios *knock on wood*, but I figured I'd ask fellow third gen owners for advice!

For the most of the time I've owned this car, operating temp has always been normal on the freeway (between 185-190 and 220), but while idling in traffic on warmer days during the summer, it had occasionally climbed up to about 235-240 at times, but never past that. I figured it was probably caused by the leak in my radiator (it's still in project stages, lol), but would add more coolant to keep things ok.

Last week, driving one night, I started overheating, so I pulled over and added plenty of water to the reservoir. The car still overheated anyway, and rather than risk it with the temp gauge maxing out, I decided to have it towed home.

Today I had a chance to tinker around with it. Replaced the thermostat, which judging by the completely shot gasket, probably hadn't been changed in quite awhile. Fired it up afterwards to let it run while feeling hoses to test for pressure/flow. The hoses remain cool, and soft, while the engine keeps heating, so it seems as though it's still not getting any coolant flow. The fan still comes on around 230 as normal, so I wouldn't suspect that.

With a new fail-safe thermostat, and more recently (within last 6 months) changed coolant temp sensor and timing done, I suspect it's one of these?

- Bad radiator cap?
- Clogged/blown radiator?
- Bad water pump?

Also, these are other things worth noting
- Hoses appear to be ok (no visible cracks or any of that)
- No bubbles forming in coolant reservoir
- Visible leaking out the front nose? (I find it a bit odd since it's a little bit away from the radiator)
- No milky stuff in the oil or on the oil cap
- While the car is sitting for a bit after I turn it off, I can hear what sounds like the radiator trying to suck in coolant, but having trouble.

Is this more likely a bad cap or a clog? Just wondering what I should try first, thanks!

 

When your engine warms to the thermostat temp, it should open and your upper radiator hose should get hot from the coolant coming out of the engine. If that's not happening your thermostat is not opening and allowing coolant flow. Either bad thermostat or faulty installation. Fix Check water pump by leaving radiator cap off and starting the car. You should see water going out and coming back in the return hose from the heater or bypass line.

 

as said above is your coolant flowing?

does your upper hose get Warm at all?

I had to get a digital thermometer from Harbor freight, which was 25 bucks but gets the job done

my problem was my fan would never turn on until the gauge would read full hot, turned out the gauge was bad, not to say that's your problem, but i learned alot about our cooling systems hunting down that problem

 

Nope, that's just it. I let it run and warm up while feeling the upper radiator hose for coolant flow, but nothing. It stays cool and you can tell nothing is flowing through it. I just put it a thermostat yesterday, so I wouldn't suspect that, but I suppose I can pull it out and check it out tomorrow just to double check. And I wouldn't suspect a bad temp gauge either, since the fan comes on at 230, and when I did overheat with it the night I had it towed, I popped the hood, and there was definitely a bit of steam coming out from the engine (not badly, but was definitely overheated).

So since I'm still a n00b with cooling systems, is coolant supposed to flow through the radiator/use extra from the reservoir to the water pump/engine, and it's supposed to flow out when the thermostat opens, back into the radiator? The thing is, it's not just the upper hose that isn't getting any flow. None of hoses are. They all stay cold while the engine keeps getting hotter.

 

It almost sounds like your water pump is doing nothing. Can't imagine how it could suddenly fail to move any water though. When you start the car with the radiator cap off, what do you see when you look into the radiator while it's running? And I assume that when you put in the thermostat you installed it with the side with the spring down

 

The upper hose shouldnt warm up gradually it should get hot right away when the thermostat opens. The easiest way to check water pump flow is to see if your geting flow from the heater hose that goes into the passenger side radiator tank. if that is good. verify if it gets hot all the time or just while driving, you may have poor flow through radiator I have also seen an excessive amount of leaves and debris plug the front of the radiator up causing no air to flow through.

 

One very easy way of knowing if your water pump is good, is to unclamp the top raiator hose from your radiator and turn the car on for a few seconds, if no water comes out of the hose then your pump is no good. Even when the thermostat is closed a bit of water still gets by if your pump is doing it's job.

 

Well, I still haven't actually had much time to fire this thing up and play around with, but I did take off the radiator cap to get a look inside to see what it looked like, and oh boy! the PO definitely did not take proper care of the cooling system. Plenty of corrosive goodness was found, and the leak has only gotten worse. It's safe to say the radiator is pretty much toast, between likely clogs, and leaks.

Just to be on the safe side, I'm going to just replace both the radiator and the water pump. Water pumps are cheap enough anyway.

Since it's been running on a crappy radiator for awhile, should I go get an engine flush after I install the radiator and pump and have it drivable again?

 

I don't think you need an engine flush, you need a cooling system flush (yes there is a difference so don't say "its the same thing") I would flush it all out really good. The dealer has a good chemical you add to the radiator then run the car for a few days. Do it before replacing any parts, maybe it'll clean out the radiator and save you some dough. Then you won't go replacing a water pump only to have gunk ran through it again. Make sure if you use the flush solution you drain it and fill it with water until water comes out clear. Then top it off with 50/50 mix of distilled water and green antifreeze.

 

Also, check for swollen heater hoses and radiator hoses. You could have a pressure loss because of a bad radiator cap. Man,i got a 12k TA and it over heats without being used much. But i'll tell you in the winter it's like a desert with the heat on. For obvious reasons almost all 3rd gens heat up. Damn,metal and cast iron parts. Durable as hell but hold heat way too much.

 

If you aren't getting any coolant in the top hose or the lower hose then you have two possible issues. Either the water pump has gone bad. Or the thermostat isn't opening. I just replaced both and it seems to be working quite well.
Best of luck.

 

10 years later !

 

I'm 21. So I wasn't aware of this at the time. Just thought I should add my two cents. For people who come across this forum. 🤣

 

Good afternoon,

I am a newbie in this forum, I send a solution to everyone and I tell you where I am from and my problem with my car pontiac transam fiebird 1987 V8 5.0L, well first of all I am from Hermosillo sonora Mexico.

I have a transam since I bought it, the car overheats me running, I have been watching your comments and I observed about the air dam, which I ordered to make an iron one, and the overheating problem was not removed, I put a 3-line radiator , thermostat, water pump, direct fans, and even the temperature rises.

If you observe the temperatures in the state of Sonora, there are times when we reach 50 degrees Celsius, which in degrees Fahrenheit of you is 122, I would like to see if you could give me options of thermostats, where to ask for a pump, or tips to solve this and be able to show my car on road

Greetings thank you very much ...

 

If you replaced all of those things and don't have major leaks the only thing possible that you could have a problem with, would be air in your system. Did you properly bleed your cooling system of all the air? Did you run the car until the thermostat opens up and put more coolant in until it won't take anymore. Then once the air bubbles stop coming out of the radiator, make sure the reservoir is full as well. The only other thing about these third gens that matters. They have a little plastic ramp that guides air into the radiator. If that isn't there then you will overheat anyways. Also make sure that your radiator fans are turning on.
Also, when you are bleeding the air out of the cooling system, while the engine is in you need to grab your upper radiator hose and squeeze it. Do this a few times to force the air out of the system. You should do this with the rad cap off so the air can come out.

 

thank you,

I will carry out those tips, another thing could help me with the measurements of the air dam and how it is placed correctly

thanks greetings...