I've been losing quite a bit of coolant since the rebuild, about a coke can full every 200 miles. It's coming through the overflow while boosting as far as I can tell. It will spew coolant out the overflow (if I don't top it off every day) until the radiator's completely empty and it overheats. Why??? Help!

Symptoms:
- Using Greddy 18.5psi radiator cap, it's still definitely bypassing.
- Stock cooling system, stock water pump w/ 65k miles
- Gurgling/trickling noise for 30 secs after startup in dashboard.
- No oil in coolant, no coolant in oil.
- Not losing oil, just coolant.
- No leaks at all while parked.
- 50/50 mix coolant & water
- Only happening since rebuild.
- OEM Coolant gauge stays normal, slightly below middle at all times.
- Heater is WAY hotter than before rebuild. The air burns your hand.
- 9psi boost, high EGTs, some detonation
- Heater dies/cuts out shortly before engine overheats.
- Smell of coolant after boosting hard.

Thanks guys.

have u checked ur themostat(sp?)
Iv had this symptoms, luckly it was during winter, but check it, maybe it could be that simple.

thermostat. and most likely a bad water temp sensor.. or clogged water pathways in block/head.

EDIT: make that Definatly a bad water temp sensor.. that's why your gauge always stays in the normal.. and you are overheating cause your fans aren't kicking on (since they run off the same sensor).

both my thermostat and coolant temp sensor went bad at the same time. so if i step on the gas my temp neddle would go down to C and when i let of the gas it would idle normal then head towards the H slowly, and sometimes at idle or so it would boil ( tank ) and flow out the tank... also my thermostat was bad which cause part of my problem. i would check the thermo to make sure it opens bro. its really cheap...
but it might be that water pump bro...
Michael 99gs
HRC Stage 2 @12psi
Stage 3 process begins gathering parts for rebuild
2GNT Member #32

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I'd have to say temp sensor. I'm hearing that the engine is actually overheated when the guage says normal, which already means a faulty sensor, causing the coolant not to be circulating like it should (whatever that bypass path is called when the engine is first started and warming up). Temps go up, so pressure goes up and it boils out through the resevoir. After boosting when you smell coolant, was the tube leaving the resevoir (to the atmosphere) leaking a few drops of hot coolant (or is that what you meant when you said as far as you could tell it was coming from the resevoir, sorry couldn't tell). That gurgling sound you hear can come from a low coolant level, I believe. Good news that there is no cross contamination btwn oil/coolant!!! Maybe just a coincidence that it happened after the rebuild.

I know it's a stupid question but what are the fans doing?

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this might sound stupid , but i was having the exact same thing as you man , but i just swapped in a bew radiator and problem fixed. sucks putting in wome water and anti-freeze every so hudred miles. It happenned after boosting also, but was partially present during pre-turbo times.

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Well, one problem with the coolant temp sensor is that it sits so high up in the system. If you are down some coolant, then that sensor is measuring the air that is sitting above the coolant, and will read normal, while the motor is really running extremely hot. Some 4G63 guys have warped their head without seeing an increase in temperature.
Just be careful...
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Gurgle noises in the car are usually a bad heater core. Either way, if there's a leak in the system, you have no pressure and so the water/coolant is going to boil at a lower temperature and boil out which is what sounds like is happening. Try bypassing the heater lines and see what happens.






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Do you see the trails coolant leaves near the overflow tank? It will leave stains to show you where it is comming from. If you don't see it around the overflow tank then look under the car at the water pump. BTW when you rebuilt the engine you re used the same water pump, or you replaced it with another stock unit? Did you use a new gasket? These guy's are right too though, check the thermostat and sensors as well. I would just look at all possibilites from the outside before pulling anything apart. Water pump, thermostat, heater core, rad. Look at all these and don't forget the lower Rad hose.

I edited to the wiki!

Thanks for the help!

Another idea I had, is this BS?: Could I have hooked up the heater core or cooling lines backwards anywhere? I remember there being two lines right under the throttle body I might have mixed up. That might at least explain the gurgling and supah-hot heater.

Waterpump - I reused my old pump, new gasket. How would you test a water pump?
Thermostat - Will replace, likely the problem.
Temp Sensor - The temps do shoot way up when the radiator goes completely empty. *shrug* I'll try it though.
Clogged water pathways - Likely ... how would you open these? Bottle of cooling system cleaner or smth?
Fans - They both kick on normally, when they should.
Overflow Tube - Definitely where the coolant is leaving from. I made an impromptu catchcan, melted tho
Chamuko - Was your old radiator damaged? Fins flattened, etc?
Heater core - Where the hell is it? In the dash or smth?

I'll look really carefully for leaks, although I don't think there's enough coolant being lost to actually drop the water pressure. It just seems to boil for no reason, I'm thinking it's gotta be either a circulation flow volume or mis-routing problem.

yo dan what you doing this weekend, we can get together and check that shit out

lates
james

Rest In Peace Heidi Doggy

I'm having the same problem with my '98. I've already chenged the thermostat, but at idle, the temp goes up (I avoid drive thrus). My fans still come on though, but the engine heats up pretty good. I live in Phoenix, so I need to get this taken care of quick before summer brings that 120+ degree heat. Any advice?
-Sir Zyrion
"Gemini GS"