odd way of leaking coolant
 

so i recently bought a 1988 N/A rx7 and have a few questions...

it starts fine and the such but the car seems to leak coolant when it's parked on a downhill. it pours out but it isn't hot to the touch. when i park it in my garage, it leaks, but i'm guessing it's just the last of the coolant that has already coming out from sitting on the downhill.

when i pulled out the hose from the coolant resevoir, it sounds like it's burping air and releasing steam if that makes any sense...better yet, it sounds like someone is blowing bubbles and this also happens to the hoses behind the engine. i tried looking into 'burping' the car but i can't seem to find the air bleeder plug to try to release what i'm assuming is air in the cooling system.

now i've done the coolant seal test how you look for bubbles from the radiator when it's stone cold and also the one how you remove the fuse and start the car to see if any coolant comes out and they're both negative.

any input or ideas as to what's wrong is very appreciated!

where does the coolant leak from when you park facing downhill? is it pooling somewhere and runs out when on a slope?

it bet that you have air in your coolant system and not maintaining enough pressure to prevent the coolant from boiling. top up you coolant system and bleed the air from the plastic screw on top of you rad AND from the coolant line on the back of your throttle body.

it comes from the resevoir overflow hose and just waters down, it steams, but like i said, it's not hot hot. this is when the car has been driven, so the it's been warmed.

now when you mention to top off both the filler cap and the radiator one, i understand that...but where is that bleed screw? i tried looking at guides online but all of them have the pictures removed...

a picture of the locations...
http://img96.imageshack.us/img96/356...engineedit.jpg

i can't find the bleed screw unless it's the one right next to the pressurized cap on the radiator (well it's on the left of it)

The fitting next to the rad cap is the low coolant sensor, not a bleed screw.

You need to pressurize the cooling system and begin isolating the leaks (BTW, it's not a "leak" when coolant flows from the overflow tube on your reservoir).

The bleed screw would be here:

https://www.rx7club.com/attachment.p...1&d=1265245533

I say "would be" because I'm not familiar with the rad you have, with that center cap. You may not have nor need the screw because of that cap; it's at a higher point than the screw would be.

The 'bubbling' sound is your coolant boiling. This is consistent with your overflow bottle overflowing. The coolant is getting super hot, expanding and looking for an exit point which the bottle provides. You need to find out why your coolant is boiling.

I would look at:

- thermostat (is it not opening?)
- water pump (is the impeller damaged, or the belt slipping?)
- coolant (is the mix so far off (too little water) that it isn't moving heat worth a damn?)
- other

The cheapest and easiest things to do are the thermostat and coolant. Get a new thermostat from the dealer and slap it in. I wouldn't even bother testing the current one, it isn't worth the time. The coolant you could test with a tester, or just replace outright. Again, I'd just replace it.

Also, do these things one at a time and then run the car after each. If you just charge in, do work on 6 things and then afterwards the problem is gone, how could you know what caused the problem in case it crops up again? Be deliberate and systematic.


[edit] Looking at your picture some more -> are you saying that coolant is also appearing behind the intake manifold?

Now that you mention it, the temp gauge doesn't move at all after I've driven the car for a bit. That sounds like a bad thermostat symptom, right?

I've also noticed that the coolant was dirty green in color and some specs...maybe dirt or something.

Edit: I mean that there's the same bubbly noise coming back from the back as well...at least I think there is.
also, thanks for pointing out my mistake, clokker

Typically I'd agree with your "one thing at a time" procedure but that's kind of difficult- and expensive- to do with the cooling system.
Every time you break the loop you'll need new coolant and antifreeze is not a trivial expense these days.

I'd pressure test and replace whatever hoses (heater core, thermowax...whatever) are worrisome along with the thermostat and coolant, all in one go.
The primary objective here is to run leak free, the "why" is of secondary importance.

That aftermarket radiator will not have a air bleed screw.

if the only "leak" is coming from the overflow bottle it, it is doing what it was designed too do and will continue to do so until your fix the cause.

lets start simple remove the small hose from the back of the engine, it connects to your throttle body. pour in water until it starts to spill out of this hose. then quickly put the hose back on trying to let as little air as possible into it.
start engine and see if the problem persists. next step would be replace the thermostat and replace coolant with a 50/50 mix this step might cost you 20$ at most.

Nope. The stock temperature gauge in our cars is... not the best. But if your coolant is boiling but the gauge isn't climbing, I'd suspect that the gauge (and/or sensor) is either kaput or the gauge needs to pulled from the dash and cleaned.


You won't be able to tell the condition of the coolant from just looking at it unless it's some grossly wrong colour. And even then... once upon a time I helped a friend change the coolant in his 6 year old Hyundai Stellar. It didn't have temperature issues, but I was doing mine and he thought it would be a good idea to do his. The crap that came out of his car was indistinguishable from muddy water. It had probably never been changed before. We flushed it 3 times before we started getting clear water back. It had that shit in it, he had been driving it like a go-kart and it still didn't overheat.

I wouldn't worry about a little bit of debris floating in it.


How so? Replacing the thermostat might see a slight loss, but it's at the top of the loop. Ditto the water pump. If replacing a liter of mixed coolant is too expensive, then I submit that he has far greater problems to deal with than his car. :)


For you, sure. For me, I'd want to know. rookie will do what he wants. :)

hmm my Koyo one and older aftermarket one came with a bleeder screw

why is it that everyone always neglects to mention the most obvious possible issue?

radiator cap.

Karack, I believe you solved my issue. I just put in another 13lb cap and after driving the car for a few miles, and parking it, the sound was almost completely gone. It sounded like there was coolant moving around the upper radiator hose but that was about it.

Would it still be wise to change the thermostat since the gauge still isn't responding right? The dial hangs around the 3rd mark down which is pretty low and the coolant since it's a dirty green color, huh?

PS: All you guys are awesome for the advice!

on an S4 the temp gauge is supposed to only be around 1/3-1/4 at normal operating temperature.

yea i would suggest replacing the coolant if it's looking dirty, if you replace the thermostat ONLY replace it with an OEM replacement. meaning one from the dealer or mazdatrix or atkins, etc that sell OEM parts, not an aftermarket one like from kragen, autozone, etc.