Hey guys, ran into another problem last night that has me a little concerned. Was taking the car up on a little road trip yesterday when about half way there my low coolant light came on. Stays on for a bit then shuts off, comes back on for a while, shuts off, ect. My temp gauge never fluctuated. About a half hour from our destination we stop for a bite to eat and I fill up on gas. During that time I check my coolant level and sure enough my reservoir tank is dry, and you couldnt see coolant down my radiator fill neck. So I add some coolant to the radiator(didnt take too much) and fill up the reservoir to the hot line.

All is good up the our destination. Car sat for a while long enough to cool down completely and before leaving I check and the overflow tank is good, and coolant is visible in the coolant neck. We leave and all is good until about 2 hrs into the drive low coolant shows up again. All this time the car is running fine, temp gauge is staying steady. We stop again at the next gas station and to my disbelieve the overflow tank is dry...AGAIN! Before getting out of the car I can see steam coming out from my hood and cowl vent, but my engine is not overheating. And it smells of hot coolant. Temp outside is around 20F so the steam could probably be just from contacting the engine block?

I check my oil and it seems clean, with my oil fill cap clean underneath also. What the hell would cause the car to loose this much coolant in that short of time!? Im leaning towards a head gasket but isnt temperature fluctuations a sign of a head gasket since its forcing pressure(air) in your cooling system. Also what is causing the coolant steam on the engine...almost like its hitting hot exhaust but I cant tell where its coming from. Leaving the car idling I cant see coolant anywhere on the ground under the car. I limped it home and noticed when shutting down I can hear bubbling coming from somewhere by the firewall area(from inside the car)

What gives? Ive had coolant issues with this car before, but it was a visual leak somewhere on the RH side of the engine(not water pump) and you would see coolant dripping on ground off the frame. I put in a little bars leak and it seemed to fix it. Now this..

I love monte carlo's, Im on my 2nd, but this car has been nothing but trouble for me since I have owned it. Currently I have 155k on her.

 

I'm not savvy on the '98 Monte, but my guess, heater core.
- If it was a head gasket OR intake gaskets you should see evidence of coolant in the oil. Plus, you lost a LOT of coolant in a short time, I've never heard of intake/head gaskets moving that much fluid. You might also experience white smoke from the exhaust and sometimes performance problems.
- As for the temp not over heating, first keep in mind how cool the outside temp is, that has part to do with it not over heating.
- I know on cars like my '94 Grand Am, GM designed so when I heat core blows, the coolant does NOT flood your interior carpet. It allows the coolant to escape through the condensation drain (since the coolant is hot, it will steam as it flows out).
- If the water pump is bad, you should see a line of coolant on the hood insulation above the belt (and if it is the pump, based on your coolant loss, the insulation should be soaked).

Check your hoses for rips or blow outs. There are probably two thin/tiny hoses from a black coolant rail that go in and out of the throttle body. You can get a radiator pressure tester from the parts store, you can use that to safely pressurize your cooling system and inspect for leaks. You can listen for hissing sounds and see where it's flowing from. Hope this helps.

So far, my guess is heater core.

 

Thanks for the reply, I guess I never thought of the heater core leaking. I guess I've always heard when they go you get it all over your floor...or smell of strong coolant odor in the car.

I just checked the oil again today after the car sat overnight and the oil looks fine. Changed about 1k miles ago and still looks amber/brown.

Ive got a chilton manual at my rents place. I'll head over there maybe this next weekend and look up some info about the symptoms and see what it takes to replace the core.

 

Check your water pump and all hoses, you may have a small leak

 

Say it is the heater core...would I not have evidence of coolant somewhere? I havent looked all that closely yet in the engine bay, but under the car I dont see any coolant on the ground? And there is no coolant on the floorboards?

When I have some time I think I will refill everything and let the car run for a while and see if I can notice anything. Freeway speeds were around 75...rpm was around 2200-2300 hundred. Maybe the increased flow from the higher rpm is pushing it out of somewhere. I'll try and update tomorrow but others feel free to chime in if you have any idea's

 

If it isn't a pinhole leak, burning off, then it is a gasket problem. The heater core is in the dash and the car will reek if that's leaking. If you're wondering if it's a head gasket, do a compression test. How's your dipstick looking? It must be consistent with no bare spots on the stick. If not, it's a gasket issue. My guess is a pin leak or an intake gasket. Or water pump.

 

Dipstick looks fine, no bare spots and not milky. Im not going to have a chance to look at it today since I work 2nd shift I will get going to work here soon but I will try and get a better look at it tomorrow. Hoping for a pinhole leak somewhere even tho it seems like a lot of fluid in a short amount of time.

 

Well I dicked around with it today and didnt really get anywhere. I ran it for a good 10-15 min varying the rpm looking for any kind of leak and got nowhere. The only thing did notice was a slight film of coolant on the upper coolant hose when I opened the hood. A bit on top of the hose down by the thermostat outlet, and again on the top of the radiator hose inlet before it heads down to the radiator. . Top of the hood insulation seems to be dry, as well as the area around and under the water pump.

pinhole leak? Would you see it with the naked eye with the engine running? Whatever it is within 2 hrs it runs the overflow tank dry so I would sure think you would be able to see something?

 

Could be a tiny leak on a hose, but you expressed a lot of fluid loss fast.

Go to the parts store, get the radiator pressure tester, pressurize the system to about a pound or two shy of what the cap says it's rated for. Look and listen for leaks (you may hear hissing, something you cannot do with the engine running). Plus, with the pressure tester, you can see if the pressure drops at all.

 

planning on renting a pressure tester this weekend and try to get to the bottom of it.