DOHC Vobra

I've searched through a bunch of posts, and found similar issues, but nothing exactly like the problem that I'm currently having.

Car is a stock 93 Touring, I've replaced the AST (split at the seam in the plastic bottle, and was leaking) about six months ago. The coolant leaks have stopped, and all seems well except that I noticed every few weeks I need to add coolant, (about 3-4 oz), and hear what sounds like air in the heater core (at 3-4k RPMs).

The car doesn't run hot, and also isn't spitting any white smoke out of the exhaust.

I'm thinking that there's either still lots of air in the cooling system (which I think that I would have burped out by now), or that there's some type of internal leak somewhere.

First thing I'm planning on doing is getting a coolant pressure tester and see if the system holds pressure... any other ideas before I jump into figuring out what's going on here?

Thanks guys!
Justin

DaleClark

iTrader: (55)

Is your overflow tank filling up? If so, it could be a problem with your pressure cap.

May also want to get a Lisle funnel and run the car up to temp with the funnel attached and make sure you've burped the air out. When doing this make sure you have the heater on in the car.

A cooling system pressure test may help as well, you may just have a VERY small leak that's hard to find. For coolant leaks I find my nose is the best investigator, I can typically smell a leak way faster than I can see it.

Dale

1QWIK7

iTrader: (33)

Are/were you filling at the ast or the filler neck?

When you fill at the filler neck, squeeze the radiator hose right under it as your pouring slowly. You will see bubbles and the coolant seeping downward.

Sometimes when I think its fully I squeeze the hose then it gets sucked down. That's how I know its not full yet.

DOHC Vobra

Dale,
Great ideas, I definitely need to check out the overflow and see what's happening there. Thanks for the tip of the Lisle funnel, never seem one of those before, but it definitely looks like a handy tool to have around!

Justin

DOHC Vobra

Filled from the filler neck, and did the little trick that you mentioned while filling, but it's a definite possibility that there's still air trapped in there, hopefully it's just that simple!

Justin

Reno_NVFD

iTrader: (2)

You can get the funnel from summit racing or amazon.

http://www.summitracing.com/parts/LIL-24610/

http://www.amazon.com/Lisle-24610-Sp.../dp/B001A4EAV0

DOHC Vobra

Thanks for the link Reno... gonna order one of those up now!

Justin

1QWIK7

iTrader: (33)

When you were doing it, were you squeezing it repeatedly?

I forgot to mention that after reading my post. While you're filling, squeeze the hose (around the middle part couple inches down from the hose clamp to the filler) repeatedly, like you're squeezing a ketchup bottle.

Or you can fill the neck til it reaches full, then start squeezing the hose repeatedly. You will notice the coolant seep down into the system, like its being drained lol, and just repeat the process.

DOHC Vobra

Yeah, that's what I was doing too...noticed that doing that while filling definitely allowed the system to be able to take more coolant.

Thanks!
Justin

DOHC Vobra

Update:

Well, the funnel is definitely a great tool, thanks for the recommendation guys!

The bad news... It's looking like it's a bigger problem than just trapped air pockets. I went ahead and attached the funnel, started the car, and let it get up to temp. There weren't any really big air bubbles, but a constant stream of bubbles (that didn't stop, even after 10-15 minutes).

Here's what it looked like:

http://www.youtube.com/watch?v=PPAdluTOq4I

I also checked the overflow, and it was definitely lower than when I initially filled the system.

From a quick search, it seems as though coolant seals are the most likely culprit of this type of issue.

I think the next thing to do is go and get a pressure tester and see what happens there.

Justin

AzEKnightz

iTrader: (24)

that doesnt seem like air bubbles. More like water flow from water pump pumping fluid. If it's air bubbles, coolant would slowly move downward as more bubbles are burping.

Check to see if you have heat inside passenger compartment. If so, you've burped it already.

pressure testing would be the next step as u mentioned. report back after result.

-AzEKnightz

DOHC Vobra

Yeah, definitely had heat in the passenger comp, I'm thinking that it's less "air" bubbles, and maybe more likely that its bubbles from combustion getting into the coolant passages, in which case, the coolant level wouldn't change in the funnel.

Hopefully I can find a pressure tester this weekend!

Justin

Montego

iTrader: (1)

I hate the champagne bubble test... All it does is make the owner worry and not provide any definitive answers.

RCCAZ 1

iTrader: (10)

When you get the pressure tester, make sure to use the adapter and test your pressure cap as well as testing the engine. I went through about a 6 month period where I was convinced that I had a bad coolant seal, only to go BACK to the cap, and sure enough, it was bad. Attach your cap to the tester and slowly apply pressure. If it's a 13 psi cap, pressure should build and "crack" just above 13 psi. Leave the cap attached with pressure applied, and if it drops off by more than 1 psi in a few minutes, you likely have a bad cap. I actually took my tester with me to NAPA and had them pull 3 13 psi caps off their shelf before I found one that would crack and hold pressure.

If your coolant seals are failing you'll know it. Apply the tester to your engine and pump it up to 16 psi and see if it holds pressure. If it drops off, look for leaks as you may have a small leak in one of your coolant hoses. If you have a bad breach in your coolant seals you'll eventually get coolant in the combustion chamber that will foul out spark plugs in either the front or rear housing, resulting in a "chugging" sound on startup due to plugs fouled by coolant and the engine only running on 1 rotor.

DOHC Vobra

Great info, thanks so much! I'll definitely be checking out the cap.

I can say that I've had some odd cold starts lately (engine idles rough right after startup), which I've attributed to only driving the car once a week. Revving it a couple times seems to "clean it out" and the engine settles down to a normal idle. Checking the plugs sounds like another good thing to add to my list of things to check!

Thanks again!
Justin

Zoolander

iTrader: (8)

I had the missing coolant with no visible leak problem and also the hissing bubble sound for years. Checking the coolant level and topping off as necessary before a drive was routine. Sometimes it'll be bone dry in that overflow tank. Then I got the DIY bug and replaced the stock AST, radiator, both caps, and about 11 of the 14 coolant hoses. What a PITA but it definitely gets you more in touch with your car. Afterwards, I was happy to see that there was no more missing coolant! I was sure it was a bad seal but I guess it was just a small leak somewhere. (One of the bigger hoses had green crud on it.....probably the culprit.) It gets so hot in there that it must just evaporate. I wanted to do a pressure check but Autozone didn't have the correct cap. I still check the coolant regularly, but I'm more at ease these days.

Good luck!

ksu-chewie

iTrader: (14)

I have a similar problem where I can hear the water moving through the heater core when the car is cold.
I've replaced the hoses that go to the radiator, turbos, and the hardline to waterpump housing from the throttlebody.
I have no loss of coolant, pressure test is good, and I've been using my lisle funnel to burp as well.
I can only guess if there's a leak it's the line that goes to the throttle-body from the rear iron, the lines to/from the heater core, or the heater core itself.

As mentioned in my thread, I'm going to up the temp on my fans on my pfc to make sure my thermostat is fully open when burping to make sure there's not hidden air pockets.

DOHC Vobra

I was finally able to do a pressure test this weekend... just an FYI for anyone trying to use the AutoZone rental tools, they don't come with an adapter to fit the FD's filler cap. I ended going an picking up a tester from Harbor Freight, which came with the correct cap.

Anyway, first I tested the AST cap, it's labeled as a 0.9bar cap, and when attached to the pressure tester opened up at about 13psi. I also checked the filler cap for leaks and that seemed to hold pressure just fine.

Second, I went ahead and attached the pressure tester to the filler neck and pumped the system up to about 15psi, the AST cap opened at about 14psi or so and immediately bled off some pressure (down to about 13psi), and I heard coolant being dumped into the overflow bottle, good so far.

I figured at this point, I'd leave the pressure tester connected and see if the pressure would hold. After about an hour, it had lost about 2 psi (now sitting at about 10psi)... hmmm. Figured i'd leave it longer and see what would happen. By the next morning it read 7psi.

After a little more reading, I decided to try another test this morning. Simply run the car for a few seconds and see if it was pressurizing the cooling system. So, I pulled off the pressure tester, added water (there was again none in the filler neck, and it took a few oz.), put the filler cap back on and started the car. It cranked VERY slowly, then fired up, idling very rough. At this point, I shut it down, since it seemed something was quite wrong.

I then pulled the filler cap, and coolant came out... not a good sign. I also thought at this point I'd better check the plugs and see if they're wet. I pulled both lower plugs, and they seemed dry, so put them back in. For grins, decided to try and start the car again, and this time it just cranks, with the occasional muted pop out of the exhaust.

Well, sorry for the lengthy post, but that's where I am now! I'm almost thinking that a compression test might be the next logical place to go?

Thanks guys!
Justin

RCCAZ 1

iTrader: (10)

Pretty sure the correct way is to leave the cap on the fill neck and attach the pressure tester to the AST (i.e., remove the pressure cap). Then pump it up and see if it holds pressure.

RotaryEvolution

iTrader: (30)

i agree, it's a worthless test that has been passed on for far too many years.

to find a coolant leak, use a cooling system pressure tester. that is your best and most definitive test. if there's no external visible signs of coolant leaking, yet you have coolant on your plugs after the test, well there you go.

yes, to test the integrity of the cooling system itself install the pressure tester to the AST, to test the AST cap and the AST cap seat switch the pressure tester to the top of the filler neck to see how much pressure the AST/cap are holding at, if below 13PSI replace the cap. if with a new cap it still is pushing coolant into the overflow then replace the AST as the necks have a tendency to pull and warp.

you can also simply pinch the line from the AST to the overflow tank if the system keeps pushing it into the reservoir just for the sake of completing the test for results of engine seal integrity(same as putting the pressure tester on the AST itself).

generally speaking i find that the AST doesn't hold pressure appropriately, usually caused by faulty aftermarket caps.

DOHC Vobra

Thanks for the tip, I'll definitely try to figure out how to put the tester on the AST. One reason that I haven't tried that yet is that my AST (Tri-Point) overflow hose/bard rides up very close to the neck of the cap, and while it just barely lets the cap fit on there, the pressure tester did not sit nicely on the AST (because of the overflow tube), and won't get a good seal. I'm guessing that I'll also have to block off the overflow barb, since it will be 'open' with the pressure tester (there's no plunger/seat to seal with like a real pressure cap)

Again, thanks to everyone for your input!

Justin

DOHC Vobra

Re pressure tested the cooling system last night, this time with the tester on the AST (capped off the overflow). Similar results, ended up loosing about 4psi over a 10hr timespan.

Also checked the plugs this morning after pressurizing the system and cranking the car a few times. Plugs definitely wet with something. There's a slight fuel odor, but I'm pretty sure I'm smelling coolant on the plug tips too.

Justin

RotaryEvolution

iTrader: (30)

make sure you remove the EGI fuse prior to cranking, that will eliminate any fuel from entering the engine as it de-energizes the injectors. unless if the injectors are leaky then there is nothing else in there that can be wetting the plugs down. removing the EGI fuse also kills the pump so no pressure generation still eliminates injector leak down after a period of letting the engine dry out.

still not sure? put a lighter on them for about 10 seconds and see if it dries out or won't burn(coolant won't burn).

DOHC Vobra

Thanks for the tips! I actually did pull the EGI prior to cranking (I'm paranoid about flooding the thing after all of the reading that I've done here!). Anyway, I'll give your ideas a shot and see what happens!

Justin

DOHC Vobra

Well, there's no question anymore, did one last test last night after leaving the coolant system pressurized for a bit. Removed all plugs and cranked the car (with the EGI fuse removed), quite a bit of coolant came out of the front rotor spark plug bores, and this time, it was without a doubt coolant (a good size puddle on the ground).

Thanks to everyone for all of the tips and input! Now to find out if it's an o-ring, or something worse (cracked housing???)

Again, thanks guys!
Justin