Overheating, rusty coolant, and I don't think its a bad HG

[aldend123]

I've got a 2001 Galant 4 cylinder and ~120k that had a sticky thermostat a while back. The thermostat was replaced, coolant was topped off, and the problem was solved. Until several months later when the car was overheating during acceleration, specifically it seemed to be during harder acceleration such as from a stop or slightly aggresive driving. We aren't talking about anything over 4500rpm though. The temp needle would climb past it's typical middle position into the upper range, but not touch the red. It would settle back down during calm driving or running the interior heat.

Discovered a majorily rusted radiator system which was a bit of a shock. The water was just pure rich iron brown, with caking under the radiator cap. No milkiness, no apparent oil mixing. We replaced the radiator cap, the thermostat, and ran water through the block and through the radiator. We filled it with Prestone's Cleaner flush mixture, topped off with water, ran it for 6hrs of drive time, and dumped it. Ran water through the system again, and everything seemed to be quite iron-brown still, but less intensely. Before dumping it, it still seemed to be exhibiting similar overheating symptoms. Filled again with another mix of the cleaner just to be sure we got most/all of the rust out and had planned to dump it again this week and fill with coolant.

While driving to work, it overheated badly at a stop light. Needle went for the red and no heat would come from the vents. While attempting to clean things out, did some rust jam the thermostat? Has something bad happened to the water pump? Besides this issue, the car idles and runs fine, gets expected gas mileage, doesn't loose coolant, doesn't smoke, and no signs of coolant mixing in the oil pan.

Game plan: run it without a thermostat during this cleaning period? I'm assuming by the looks of things that the thermostat is not neccesary to complete the seal on the housing? Where the hell is all this rust coming from, the heater core? Why would it heat up during acceleration? It's almost like the flow is being restricted somewhere.

Thanks for the the time!

[03chi-town0z]

if you can find someone with one of those laser-pointer style thermometers, get the car running at operating temp and check for inconsistencies in temperatures along the radiator and other cooling system components. you may have some clogs which will cause it to show anywhere from 5-25 or more degrees colder in some spots directly after the clog. another way to check the radiator flow is to remove the lower hose and pour water into the top and see how fast the flow comes out the bottom in relation to how fast you are pouring up top. a properly flowing radiator should always be able to match the speed you can pour from a gallon-style washer fluid or milk or whatever container (don't actually use washer fluid or milk, just water, haha)

also, if you werent getting heat through the vents, there may be a clog somewhere in the heater core or heater hoses to the core which would restrict the flow and limit the car's ability to shed heat more quickly, but shouldnt actually cause an overheat condition.

and if you take the radiator cap off BEFORE you start the car and then look inside where the cap was as its running at operating temperature, you should be able to see coolant flow/movement indicating that the pump is doing its job in circulating the coolant

[aldend123]

Alright, the drive home had plenty of heat. However, with the heat on the whole way, the temp gauge would ocillate up and down over a period of roughly 2 minutes from normal temp to a high temp just shy of the red and back down again. I'll be checking for flow later tonight, both at the radiator and the heatercore.

[mrg7243]

that is probably from a lack of the thermostat being there

[troubled4g64t]

basically the end result is to much water not enough antifreeze since the antifreeze also acts as a non corrosive you probably plugged the heater core w/ sediment during the flushing process what you should do is remove both hoses that run to the heater core and try to flush it out w/ a hose make a rig to clamp one hose to and screw it onto the garden hose use street pressure to blow out the heater core remove the t-stat and just use the gasket and double up on the flush in the block once you clear out the heater core then when you are all done you will prob. want to replace your radiator since you will never get out all the rust the tubes are really just to narrow and the pressure will go where it has the least resistance just like anything else.

[aldend123]

mrg7243, haven't run the car without the thermostat yet. Symptoms described had a month old thermostat in place.

The car had antifreeze in it, though I suppose the mixture might have been weak. Ran the hose through the heatercore directly, and pumped out plenty of rust-filled water (which matched what I found in the rest of the engine). Not much for flakings, but plenty of brown color. Ran the hose through the radiator, down the heatercore feed and return lines, and flushed the block as well. Pretty much every direction/combination I could think of to verify all paths were clear and all liquid had been flushed.

I can see in the radiator through the fill holl that there is deffinitely rust deposits accumulating in the core. Pretty sure it's an aluminum core, but I think it is just collecting in there. I think part of our problem was that there may have been sooooo much rust in the system that the previous attempts to flush it weren't sufficient and something tells me I'm not done seeing brown water.

We put in a coolant heavy mix to ensure no more rusting, and might flush again depending on a visual inspection and symptoms. It's the GF's car and I told her if this doesn't work, that the radiator and/or heatercore might need to be replaced due to lack of efficiency and due to the extensive amount of rust, to expect the heatercore to let go at any time.

Next thing to try that I forgot to check last night was undoing the primary line on the bottom of the radiator to measure if it drains the water as fast as I feed it in. However, just through the drain hole, it seemed to be moving water at a fair rate.

[aldend123]

Late update for future readers:

Ran the car without the thermostat, did not change anything.

Multiple coolant flushes, and finally started seeing rust free results. Checked all passanges and all were free. Radiator did seem to take liquid a little slow, but nothing shocking. Heater core let go in the process of all this, so it has been by-passed and will be replaced soon.

Without any good game plan, an ebay radiator for ~$60 shipped was purchased and installed. Still need a few more test drives, but this seems to have fixed the problem!

Thanks for the help.

[jermyjerm]

Make sure the fans are running.I'm new to TGC and I too am working on issues with the gf's 8g.This cooling fan issue seems to plague these cars.

[03chi-town0z]

Late update for future readers:

Ran the car without the thermostat, did not change anything.

Multiple coolant flushes, and finally started seeing rust free results. Checked all passanges and all were free. Radiator did seem to take liquid a little slow, but nothing shocking. Heater core let go in the process of all this, so it has been by-passed and will be replaced soon.

Without any good game plan, an ebay radiator for ~$60 shipped was purchased and installed. Still need a few more test drives, but this seems to have fixed the problem!

Thanks for the help.

glad to see the radiator solved the problem. even a single core radiator should never back-up enough to overflow from the top if you have the lower hose removed

[ShiZnitH]

Make sure the fans are running.I'm new to TGC and I too am working on issues with the gf's 8g.This cooling fan issue seems to plague these cars.

The lack of coolin fan hasnt been an issue for me. i drove a couple of months without neither cooling fan or A/C fan after my ex-girlfrien crashed the G. It stayed at normal temperature at all time. Although, the outside temp was about 10c.