[rjgss]

I am not sure where to start looking but it appears that I keep losing coolant in the lower tank (reservoir) but the top stays full. It used to last a little longer but yesterday took it to work (about 30 miles roundtrip), it was hot outside and checked it this morning and lower tank is almost empty. I have had this problem since I bought it. Engine is modified. I bought a new tank thinking it was leaking but that isn't problem. There was a spot on ground under where tank is and looks like some fluid on undercarriage. Is it possible that when it gets very hot it gets pulled out the vent holes? I don't see any lines leaking and before I start taking shit apart was wondering if anyone else has this problem. I have read about losing an inch or so after several miles is normal but this doesn't seem normal. Took out a plug and it looks fine. Thoughts?

[Thestormoverkrynn]

Don't take shit apart yet, get a disappearing ink vehicle safe dye, that can only be viewed with a black light, that way if it sprays up over ur engine u can't see it without the black light, introduce into whatever is leaking, drive it around, get the black light out ... Then .... Let the parts replacement begin! Once fixed remember to wash down whatever it sprayed out on, for two reasons, that coolant is corrosive, i believe, so is brake fluid, also so as to prevent false leak tells for leaks that happen later in the vehicles life span. Nobody likes to work on dirty engines :P

Sorry about ur issue, hope this helps. I don't support the next link in anyway i just googled and it's the first thing i found ..

https://tracerproducts.com/automotiv...%20performance.

[rjgss]

Thanks, sounds like a good idea to see if and what is leaking!

[rjgss]

I added that tracer fluid and ran car. The whole left side in an around the reservoir glowed. It’s now leaking to the floor or at least I can see it better. Losing the lower tank every trip, which is like 45 mins. Took this video but may be hard to see and it’s dripping on sub frame past firewall but probably traveling but I don’t see where it’s dripping from. Any ideas as I’m not familiar with engine. There’s hoses everywhere and it doesn’t seem like heater core
Vide: https://youtu.be/bDyUnh-i2Ck?si=xp_mZHmBSMx-tMu7
Any suggestions would be appreciated
Thanks

[Gunkk]

Well there's an obvious drip and leak showing on the bottom of the car at the end of the video. Don't see much from up top. If there was a leak in the pressurized loop (top tank and hoses and/or their tees and connections), then we would likely see evidence of spittle and spray on the top of the engine.

The lower tank has no fluid entry or exit points other than: 1) the 1cm diameter fill port, and the top tank's suction straw/tube.

Because you are not losing main pressurized loop coolant (top tank stays full). Only the makeup/surge lower tank is losing coolant. So the only possibilities are: 1) coolant is coming back out the fill tube, 2) coolant is getting sucked out the straw into the main loop as it should via suction during cool-down after a drive, or 3) there's a crack in the lower tank. We don't see any fluorescence around that fill port, and it takes a while for the top tank to suck coolant out of the lower, so I'm gonna go with #3.

Suggestion: pull the reservoir and inspect the lower for cracks/leaks. Alternately just fill the lower then pressurize it with a few PSI of compressed air and see what comes out.

[rjgss]

Yeah I was thinking that but I replaced the original because of that. Guess it’s possible the new one could be leaking. There is fluid along bottom of it on frame. I’ll get a pressure tester and check that way
Thanks for ideas

[m6-lt1]

One thing I'll point out is you may have never had a problem when you had the original tank but the new tank is defective and now you have a problem. Here's why:

I thought my lower tank was losing coolant at a fast rate and was concerned. Dealership told me they filled it but I have a feeling they did not. Anyway bought 50/50 dexcool and filled it to the exact line myself. I hadn't driven the car for a few days when I filled it.

Now after a drive I notice the lower tank is filled PASSED the line (about 2/3) which tells me I filled it to much/didn't account for coolant in other places. During my last track day I noticed the lower tank was filled up to 3/4 and got concerned. After the next session it had dropped back down to 2/3.

If the car hasn't run for a while the coolant in the lower reservoir is exactly at the line just like when I originally filled it even though it was at 2/3 when I shut off.

I've seen a lot of posts here about the coolant in that tank being low and I think it's due to the coolant slowly going back into the motor or radiator after the car has been off for awhile. When you replace the tank again factor in what I just mentioned if it is lower after not driving it for awhile. I jsut bought a syringe wo suck some of the coolant out because I do think mine is overfilled a bit even though it is exactly at the line after the car hasn't run for a few days.

[Gunkk]

Originally Posted by m6-lt1

after a drive I notice the lower tank is filled PASSED the line (about 2/3) ... During my last track day I noticed the lower tank was filled up to 3/4 ... After the next session it had dropped back down to 2/3.

If the car hasn't run for a while the coolant in the lower reservoir is exactly at the line just like when I originally filled it even though it was at 2/3 when I shut off.

What you describe is exactly how surge/expansion tanks work.

Our cars have a COUNTERINTUITIVE setup. The top tank is part of the pressurized loop. The bottom tank is the expansion tank.

So under normal operation, the bottom tank accepts excess volume of coolant from the loop when the loop is hot -- because water expands more than aluminum when it gets hot. So it needs somewhere to go, and that place is the lower tank.

And then when the engine cools back down, the coolant cools back down and then shrinks in volume and the pressure loop sucks that same "excess" coolant back out of the lower tank via the straw -- because the coolant shrinks in volume when it gets cold again.

The benefit of all this is a natural self-bleed action, so any small amounts of air that get into the pressure loop will work it's way out of the system via natural thermal expansion during and after a drive.

All of this is normal. Your car is normal.

[m6-lt1]

Originally Posted by Gunkk

What you describe is exactly how surge/expansion tanks work.

Our cars have a COUNTERINTUITIVE setup. The top tank is part of the pressurized loop. The bottom tank is the expansion tank.

So under normal operation, the bottom tank accepts excess volume of coolant from the loop when the loop is hot -- because water expands more than aluminum when it gets hot. So it needs somewhere to go, and that place is the lower tank.

And then when the engine cools back down, the coolant cools back down and then shrinks in volume and the pressure loop sucks that same "excess" coolant back out of the lower tank via the straw -- because the coolant shrinks in volume when it gets cold again.

The benefit of all this is a natural self-bleed action, so any small amounts of air that get into the pressure loop will work it's way out of the system via natural thermal expansion during and after a drive.

All of this is normal. Your car is normal.

Thank you for the explanation. I was going to make a post about this asking if I should take some coolant out. Sounds like I shouldn’t since it eventually drops to the fill line. It was kinda alarming seeing it at 3/4 but sounds like that’s normal. Guess I will just use the syringe to make brake bleeds go faster.

[Kamero6]

Buy the pump and cap to pressurize the system. Leave it pressurized for a couple of hours. If its not leaking from the actual cap, pressure should remain the same, maybe drop a pound or 2.
See if you find the water leak. If everything is ok, you might have an internal leak.
Check for combustion gases in the coolant.

Good Luck

[rjgss]

I will pressurize and check where this leak is. Part of me thinks it’s the vents in the tank or the tank because majority of liquid is under it on that channel and dripping off it at firewall
Thanks all

[rjgss]

This may be a stupid question but I have hooked ip pressure tester to cap on upper tank. It won’t hold pressure, only thing I can think of is the vent holes but then how does the system pressurize. Would think there’s some sort of valve that allows tank to pressurize or am I doing something wrong.

[rjgss]

Yep was stupid, used wrong adaptor. Pumped to 15 psi no problem but now it’s dropped 10 psi in 10 minutes and no leak seen. It’s obviously leaking when hot as there’s fluid under and around coolant tank. So then removed adaptor and screwed it on again and pumped to 17 psi, this time no drop in pressure. Could it be the lower reservoir? How do I test that? Car doesn't overheat and oil looks fine and never see white smoke

[Coded4SS]

did you get this solved? My lower tank loses coolant a bit faster than it should be. Pressure tested cold (dealer) and no drop. But I think its only when its hot