So I got my FD about 2 months ago and the PO said the motor has 13K on a recent rebuild. He showed me the receipt and the motor runs great so I believe it.

About a week and a half ago I drilled and tapped the water neck for a coolant temp sensor and I removed the upper radiator hose so the aluminum shavings wouldn't get into the cooling system. I re-assembled everything and the following week everyday the coolant buzzer would go off like 3 sec after I start it up to go somewhere. I also notice my reservoir is filling up. This happened everyday after my 5 mile commute to and from work.

So I go and get a lisle funnel and do a "champagne test." I see bubbles about 1/8" in diameter every 3 sec maybe. "F#ck my coolant seals are done

But just to be sure, I do a coolant pressure system test just to find any leaks. The system didn't hold pressure for very long but I suspected the adapter and the crappy autozone pump was probably leaking. It was late so I call it a night.

I drove yesterday 60 miles waiting for the coolant buzzer to go off and it never did. Then when I left my destination expecting the buzzer to go off again but it never did. I check my water neck and it's filled to the brim with green coolant. I drove it again this morning and the water neck is full of coolant. Everything seems to be fine

I recently changed the AST cap and did a coolant flush with prestone coolant and water-wetter. This was right before I drilled and tapped the water neck.

What it seems like is the engine isn't sucking the coolant back from the water neck on cool-down, leaving a big air pocket in the water neck. But the car seems ok after I did the coolant pressure test. I did accidentally forget to plug the line that went from the AST to the reservoir when I did the test so the first few pumps forced a bunch of air to the reservoir...maybe that free'd up some debris?

cliffnotes:

coolant flush/new AST cap

drilled/tapped water neck for temp sensor(removed lower radiator hose)

loosing coolant in water neck, reservoir slowly rising, buzzer going off everyday

performed pressure test

coolant is full, buzzer never goes off

 

Aw the good'ol champagne bubble test A.K.A heart stopper

it's sounds like you may have a air leak and therefore aleviates the pressure that is required to suck the water back in from the overflow tank. Obvious check the area where you drilled and also inpect the connection from the overflow tank to the filler neck.

 

lol I did a "block test" and those bubbles didn't turn the blue fluid yellow so I don't know..maybe it was just the water boiling in the hotspots of the engine/turbo with lack of pressure

is it possible for there to be a coolant leak without any visible signs of coolant dripping on the ground?

 

check the line that runs from the AST to the overflow tank. theres a stupid join in the middle of it...
if thats not holding pressue or is leaking then your coolant wont get sucked back into your engine under vacuum as it cools.
iv had my issues with that line, lol

 

ah ok. I was thinking that might be the culprit...I'll probably just replace the whole thing with a new hose since it looks like a bit of a b*tch to get to lol

 

I don't think you have coolant leaking into the ground. As you said:

Building on what 96fd3s said:
Reasons for that can stem from a leaky AST cap, hose, or that thermosensor you drilled through for. For example a pin size hole in the hose that goes from the filler neck to the resevoir tank would cause the system to depressurize and thus the coolant would not be sucked back in upon cooldown. Another way to look at is picture someone trying to take sip of a soda using a staw that had a hole on its side.

 

did you burp the coolant system? get one of the leslie spill free funnel and burp it properly

 

yeah but you would think that the hole would leak coolant on the ground but I didn't see anything

yeah I have one of those and let it run for a good 10 min with it on there

 

No not particularly.

 

well it started doing it again yesterday so I removed the coolant reservoir, took it part and cleaned the inside of the grimy junk at the bottom. I also changed the overflow line that goes to the AST with a solid one-piece hose. Hopefully that fixes it.

 

I had a similar problem when I first got hte car on the road , the issue was that I hadn't burped the system correctly and it would get air out of the lines and it would go up the filler neck

 

looks like changing that overflow hose worked! It must've had a small air leak somewhere..not surprising as it had like 5 adjoining sections

 

glad you got it fixed mate

 

well it was fine until this morning

Im gonna continue the process of elimination and check the o-ring in at the top of the filler neck since I had messed with it when installing that temp sensor.


there must be a tiny leak somewhere..so tiny that it comes and goes