Coolant Disappearing?

[DannyZ]

Hey guys,

I've been running into an issue with my 1996 GT 5-speed— the coolant keeps disappearing! I have to add some nearly every time I drive it. The expansion tank is empty every time I open it to add coolant. I've replaced all the coolant at this point and replaced the expansion tank cap. The sensor is working correctly because every time it pops up the check coolant light there really is no coolant in the tank. Am I not filling the coolant correctly? I fill it up, close the cap, start the engine, run it for a minute, turn it off, and then top up the coolant in the tank.

I've checked for leaks and I really can't see any— I can park it on a driveway, run it, and there are zero leaks of any kind on the driveway. There's no belly pan or anything that would hide the leaks either. The valley in the V of the engine is perfectly dry, and the coolant crossover in the manifold looks intact as well. There's no smoke from the exhaust and the engine runs perfectly.

Even when I fill up the coolant completely, the check coolant light comes back within 5 minutes of driving. Now the engine never really overheats, but I'm hesitant to drive anywhere far because of this issue.

It's also strange that this started happening just now— I drove this car from LA to Phoenix a few weeks back with no coolant issues.

 

[HawkX66]

Look under your oil fill cap and see if it's milky. Do you have a lot of vapor coming out your tail pipe? You probably have a bad head gasket and are blowing it out the exhaust.

 

[DannyZ]

Look under your oil fill cap and see if it's milky. Do you have a lot of vapor coming out your tail pipe? You probably have a bad head gasket and are blowing it out the exhaust.

I'll check that tonight! I do remember checking the oil last month and it looked fine, but I'll check it again tonight. I don't notice anything weird with my exhaust, and there's no smoke when I accelerate aggressively from a standstill. My GT is a convertible so I'd notice any weird smoke/smells pretty quickly with the top down.

 

[96blak54]

Pull sparkplugs out, keeping track of each cylinder, examine each plug to each other. The cylinder with coolant breech will show on the sparkplug ground strap. Itll be green in color

Sent from my SM-G900P using Tapatalk

 

[Silver95bird]

If the hg is allowing coolant in the cylinder, it'll take out the O2 sensor and gas mileage will plummet. Also check the water pump for signs of weeping, the oil filter adapter gasket, and dare I say it, the heater core.

 

[DannyZ]

If the hg is allowing coolant in the cylinder, it'll take out the O2 sensor and gas mileage will plummet. Also check the water pump for signs of weeping, the oil filter adapter gasket, and dare I say it, the heater core.

I wouldn't notice the gas mileage differences because neither my speedometer nor my odometer work, so I just put in gas whenever I have to. It's just really odd how so much coolant is disappearing so quickly. I've put nearly a gallon in and it just keeps disappearing.

 

[DannyZ]

Alright so I checked under the oil cap and on the dipstick, and the oil looks clean and normal with no signs of coolant. I added more coolant and realized I had been under-filling the tank a bit, I forgot that the coolant also has to go sideways in the tank— I'm used to my BMW expansion tanks that are smaller and quicker to fill. Also, it looks like my coolant crossover is aluminum, meaning it's already been upgraded to fix the plastic crossover that usually comes with the NPI intake. I guess I'll keep an eye on the coolant levels and see if I continue to have issues.

 

[NEURON]

I have a ZX2 doing exactly the same thing and even after 3 trips of over 1k it has stayed the same, this had been going on since I bought it about 3 years and 16K miles ago(111K on it). Keep thinking it will get worse and find it. Never a drop anywhere, heater works fine with no smell. It seems like it only must leak when driving, have run it hard and then let it idle with fan going and temperature up with still no signs of leakage. Flushed, new coolant, T-Stat and rad cap. Damn FWD so you cannot readily see the water pump if it is weeping but I have never had a car do something like this for so long without getting worse/failing. Not a fan of plastic/aluminum radiators and wonder if it leaks during driving so the air dissipates it so there is no evidence of the leak, but that is reaching a bit. Curious if our problem is related.

 

[DannyZ]

Yeah, I'm thinking if it's a leak it's one that's only revealed during driving. I've revved the engine plenty of times while keeping an eye on the cooling system and it's fine. The last time I really topped off the coolant was like 1000 miles ago before driving to and from LA.

I'm no stranger to weird cooling systems— my BMWs love to have cooling system issues. I had to replace the radiator and expansion tank in my 540it within a month of buying it, in 110ºF heat.

 

[07GtS197]

How does the coolant resivoir look on the top? Both my 00 gt and 02 gt would leak coolant out the cap when running hard.