Dang it my GL is still overheating pretty bad, especially when I have the heater on. I replaced the thermostat and that didnt help. It all looks normal, theres coolant in there, not leaking. It doesnt smell like burning or anything. Seems like at night when I have my lights on it overheats more, not sure if theres some short or something. Should I try replacing the sending unit sensor?

And another thing, when I turn the heater on, theres no heat really, its actually somewhat cool rather than warm, even on full blast, its not warm at all let alone hot. Whats up with that? That makes me think that the engine isnt really overheating. Could it be the heater core gone bad and not putting out heat? Or maybe the coolant hoses that go into the dash are bad or something? Ughghg. Plese help, winter is coming soon. Thanks.

Heater core plugged up; might be a cause of these symtoms.

What have you done to the cooling system up to this point? Cleaned or replaced the radiator? Do the heater hoses in the engine bay, the ones that go to the heater core, feel hot with the heater turned off? One should be considerably warmer than the other. How about with the heater turned on, they should both be hot but one still hotter than the other. Sounds like your radiator and heater core are clogged.

 

You could disconnect the heater hoses at the firewall and see if you can blow air through the heater core. Should blow freely.

Well all I've done is replaced the coolant, did a flush and replaced the thermostat. So is it easy to get to the heater core? Probably not huh? Gotta take out the dash and stuff? I'll try blowing air thru. Thanks...

Is it easy to take the radiator out and clean it? Its so dumb that the drain valve is like half way up the radiator, that is the stupidest idea a car company could ever come up with...................

disconnect the heater hoses at the firewall and see if you can blow air through the heater core. Should blow freely.

 

Try this first - it's easy to do, and no cost. You can get to the hoses behind the engine under the spare tire, if your engine compartment is similar to mine. Take off the hoses and either blow through or run water through with a hose.

Try this first - it's easy to do, and no cost. You can get to the hoses behind the engine under the spare tire, if your engine compartment is similar to mine. Take off the hoses and either blow through or run water through with a hose.

 

If you're gonna flush out the heater core like this. Do it in the opsite direction the coolant flows. You'll knock more stuff loose this way.

I had the same condition on my '90 Ford van, I replaced everything but the water pump and the gauge still went up to hot. Looking back with what I know now I bet it was a bad wire or gauge.

 

If you have a Haynes manual, there's a chart in there that shows what the Ohm resistance of the sensor should be at different temperatures. If you have a multimeter just check it and watch as it warms up and compare to the chart. If it's bad then that's all you need is a new one. If it's good then I'd bet it's a wiring or gauge problem.

 

Another thing you can do is temporarily eliminate the heater core from the circuit, just remove both hoses and loop one so one end is on the outlet and the other end just loops back to the inlet side, then you can drive around and see if that makes a difference in the gauge reading. If it does you can leave it that way until you can change the core, I have had my chevy that way for years, just can't drive it in the winter.

So if I blow water thru the core with a hose, can I apply water pressure or just normal hose pressure? Will it damage anything? Thanks.

Ya thats the thing - I gotta drive it this winter. But it overheats in the cold too, or it says it does. I tried takin the sensor out but its really stuck on there, I'll try some more.

It's almost a given that your radiator and heater core are plugged. Do a search and you'll find that some of us have managed to clean the radiator out and reassemble it without leaks. If you can't find any info let me know and I'll walk you through it. Radiators are relatively fragile though, there's no guarantee that you won't crack a tube or something in the process, especially if it's got some corrosion. I think one could clean out the heater core too. Try a stiff wire with the end bent over. It's made of brass or aluminum, so you don't want a sharp tip that might damage it. Not something as big as a coat hanger. Something like .032" - .040" safetywire or mechanics wire. Twist two strands together if one isn't stiff enough. Good luck.

You can use a hose nozzle with pressure on it. Start with only a little pressure, or it may blow back all over you and the engine compartment. Then increase the pressure if you can.

 

If the heater is blocked, you can do the loop-back that 1985glwagon suggested, then go for a drive to determine if that's the only problem before continuing. If the heater's blocked, there's a good chance the radiator is clogged up, too.

So what does the core clog up with, just rust and stuff from the radiator? I'll try the hose pressure and the wire thru it. So do I stick the wire thru the holes where the hoses come out in the engine bay?

Ya I dont know if I wanna take out the rad. Maybe I'll disconnect the lower hose on it and do another flush, would that help? I didnt do that the first time around.

Thanks guys.

If they're clogged there are chemicals out there that are "supposed" to clean a lot of that gunk out, you just put it in then run it for so long, then flush the gunky water out and put in your regular 50/50 mix and see if it worked. I used it on my van but since the radiator turned out not to be clogged at all I can't say if it works or not.

Hey guys isn't it supposed to be an easy job to take out the rad. in these subies? Just a couple bolts and it's out I think, I'd just be REALLY certain it is clogged before bothering to replace it, I spent $200 for a new one for the van and it didn't make the slightest difference.

Removing the rad is quite easy. Takes longer to remove the fan shroud, if yours still has one.

 

The rad and heater core get clogged with by-products of corrosion, combustion gases, old broken down coolant, minerals in the water, etc. Most of it gets pretty well stuck to the inside surfaces and isn't much affected by flushing. I have used the "flush" chemicals with some degree of success. However, I would recommend those for before you have an overheating problem, not after.

If they're clogged there are chemicals out there that are "supposed" to clean a lot of that gunk out,

 

These chemicals can also erode your hoses while they're in there working on the rust. If you use this stuff, any older hoses on your car may start leaking after a month or two. Hope you don't need it. I don't think it will help if your system is clogged with corosion.

 

Radiator removal is pretty easy, but you can try flushing it from the bottom first.

 

If it is clogged, you can get a new one from radiator.com for $130.00. I just went through this with mine. After all new hoses and a new radiator, it finally cooled down again.

I ran some radiator stop leak to stop a bad coolant burning leak i had, and I think it may be coming back to bite me. The car runs about 1/2 or a bit higher on the gauge, and doesn't boil over when running, but if you shut it off and wait 30 seconds, you can hear the coolant boiling in the block and the overflow tank. it boils hard enough to blow coolant out of the overflow tank.

The heater core isn't plugged, and I use it to keep the temp under controll off-road. Every part of the cooling system seems to get hot, so I don't think anything is plugged. The only problem I can see is that the electric fan doesn't kick on untill its boiling.

So is there a specific chemical for cleaning out heater cores or just any slush cleaner will do?

Ok well I did all you guys said today, I disconnected the core hoses, put a hose with water pressure thru one hole at a time, then disconnected all the hoses to the rad and ran the hose with water pressure thru there. Then I ran some flush chemical thru it and let it run for 10 mins with the heater full blast and it worked!!!!!!!!!! I had HEAT in the car, the heater put out pretty good heat, way better than last night before I did all this. Tomorrow I'm gonna disconnect the core hoses again and run the garden hose thru there again to get all the flush chemical and water out. If I start the engine without the core hoses connected, will it get rid of all the water in there?

Anyways I'll let you guys know wats up tomorrow. Laterz...

By the way if you do need to replace the radiator, go down to Spalding Auto Wreckers. I've bought three NEW radiators from them for a variety of cars for under $100 including my Brat. Best price I've found anywhere.

I forgot to say that it didnt overheat last night either, but then again I only ran it for about 10 mins and I didnt drive it.

Sounds like you're getting there. Good luck.

Flush out all that solvant junk now. Fill up your system and be sure to get all the air out. Then drive it around for a half hour and really get it upto temp. Check your heat again, make sure its not over heating, and be sure to top off the coolant system AFTER it's cooled down

Best stuff I've found for flushing the cooling system out is Mac's Radiator Cleanser, found at a NAPA outlet. Stuff works great, but probally won't clean a fully plugged heater core. HC's have very small passages in them, way smaller than those in a radiator. Once fully plugged, it be plugged.

Replacing the HC is a PITA, even using McBrats method. Removing the dash to do it the way it's supposed to be done is even more of a PITA though.

Well its still overheating but not as bad. I dont think the rad is plugged cuz when I flushed it and put the garden hose on the top, water gushed out the bottom pretty well and freely. Same when I put the hose on the side petcock drain hole... so I dont know.

Can I make the 2nd fan come on all the time continually? How? I might just do that. Well I'll try to replace the temp guage sensor first...

Thanks.

When you get it up to temp. Feel around the face of the radiator for cool spots. That will tell you if any tubes are clogged up. I wouldnt go by what you saw gushing out from the garden hose as an indicator. If you have the money just replace the darn thing

 

I put my eleictric fan on a switch. Ran the switch upto the cabin. Now I run it whenever I'm off the highways and interstates.

The best thing to do to prevent radiator and heater core problems is to drain and refill your coolant at least every two years. When adding water to your antifreeze, use distilled water as it doesn't have any minerals in it to cause you grief later on with plugging things up.

Also, IF you replace your radiator, a turbo radiator has a thicker core in it and doesn't cost much more AND it's a bolt in w/o mods.