Sucking air???

I've been testing my new aluminum radiator and posted in other discussions that my radiator fan switch was kicking-in too late. Found that I had air in the system which caused the problem and surprised me since I thought I had already removed all the air.

NOW I'm finding that after I remove the air from my system, more air is introduced after driving it. If I burp the system and let it run, everything is fine. But when I drive it again I find there is air in it. I have no coolant leaks and the coolant reservoir level doesn't seem to be dropping (although it is hard to tell with a stainless tank).

The new radiator is so efficient that everything works fine when the vehicle is moving -- even on a hot day with air in the system. I only notice a problem in stop-and-go conditions where the system is working harder.

I realized that I did not have a washer installed on the radiator valve. There wasn't one on the OEM unit either -- must have disintegrated. I've since added a fibre washer to the system but it's still sucking air

Any recommendations on how to diagnose how air is getting into my cooling system???

geekdaddy said:

Any recommendations on how to diagnose how air is getting into my cooling system???

Click to expand...

If you have an air compressor already, a few tens of dollars at harbor freight will buy a quite effective coolant system pressure tester.

You can also buy fluorescent dye (mine came from Autozone); an ounce in your coolant reservoir will make any leaks in the system glow under a black-light.

Probably through the radiator bleeder valve. Use a new aluminum or copper washer there.

Being at the top of the radiator, it is where air will tend to hide, and therefore when the system heats up only air is expelled. Then, when things cool off it draws air back in. Repeat. Someone (Jim D?) had a problem getting his to seal.

It was me

I was having sealing issues, but I think I have the lower rad support on backwards if that is even possible. My rad seems to be tipped slightly forward and is getting interference from a section of sheet metal in the nose cone. My real issue was that that piece of metal was touching right where the bleed screw goes into the top of the rad. It was so close it cut a fiber washer, bent a copper washer and sliced thru a couple rubber o-rings until I stuck my finger down in there and felt that flat piece of steel.

I was able to put a new o-ring on the screw and gently pull the rad away from the metal long enough to get the screw and o-ring seated properly. I haven't bled the rad since I got it to seal since I haven't had time to drop the rad again and try flipping the lower support. It ain't drippin', so I ain't messing with it. The car runs way cool now, to the point I suspect here is a stuck t-stat in the mix.

UPDATE...

This issue continues to plague me :huh2:

What's really strange about my situation is (1) I don't seem to be losing any coolant and (2) the system seems to be pulling air into the system WHILE it's hot/running -- not after sitting and cooling. Fortunately the radiator is so darn efficient that the system never overheats to a dangerous level. But air in the system causes my radiator fan switch to kick-in later and the temps rise a few degrees than they ordinarily would/should in stop-and-go traffic. While cruising (at any speed) the temp gauge is very steady and where it should be.

While I was underneath installing my sway bar, I noticed the drain plug supplied with the radiator had a crack in the o-ring. I had intended to replace it with a proper tapered aluminum plug anyhow so I removed it and reinserted a 1/4" npt aluminum plug with teflon tape on the threads. Upon closer examination after removing the plug, the o-ring crack was bigger than I thought and there were additional smaller cracks.

I've only driven about 15 miles since the plug swap, but I THINK this may have solved the problem. Didn't seem to have any more air in the system and fans kicked-in at proper temp when I arrived home and let her idle in the driveway for awhile.

Here's a pic of the plug I removed. If you still have one of these I recommend replacing it:

Interesting...

I'm having a similar issue. Partway into a head gasket swap because of it. Air in the system, hot running as a result, no apparent loss of coolant save what is pushed out by the air. I'll certainly inspect this o-ring seal (not ideal) next. Hard to imagine how that could work though, only sucking air in while running?

In my case I think I have a leaking head gasket that is allowing combustion/compression air to leak from the cylinder(s) into the cooling system while running, causing a large bubble in 1-2 hours of driving that then causes temperature swings. On shutdown I think it's also allowing the cooling system to leak a tiny bit into the cylinder(s) causing a smell every other startup. I'm pulling the head anyway but will inspect that o-ring.

Geez Greg...

Blowing, sucking... Hmmmm...

I think its actually BLOWING although I read your post thoroughly. I just chased down a MYSTERY leak in my Vette and found that I had a very fine and small leak at the intake goose-neck that sprayed a fine mist that immediately evaporated... so all I was left with was a little powdery dry dust.

I had pressure tested my 16 pound system to 20 pounds and found that it held what I thought to be a reasonable time... of an hour or so with the loss of a pound or two of pressure. This LAST time I took it up to 25 pounds and finally found a small drop or two coming out of the goose-neck gasket.

I ended up replacing both a warped goose-neck (17 bucks) and added a reusable gasket (19 bucks...) and my problem went away... My pressure held at 25 pounds and NEVER dropped. I found that it NOT dropping to be a minimum requirement. Always pressure test your cap as well... these testers are about 80 bucks at HF but do not have the gender-bender to test a cap. You can find old Stant Testers on EBAY that do... or borrow one from your local chain parts store.

WOW... found these on EBAY for 30 - 80 bucks... a good deal and worth their weight in gold!

Here: http://www.ebay.com/sch/i.html?_trk..._nkw=stant+pressure+tester&_sacat=0&_from=R40

And always remember this... if Air gets IN, something hasta be getting OUT... which is usually coolant.

Glad you found the problem, HTHs as well.

In my case it was the headgasket:
http://xwebforums.com/forum/index.php?posts/209018/

Good theory, but...

Took the X for a spin to heat things up and evaluate the new drain plug install. Still sucking air :drink:

I may follow Tony's suggestion and find a pressure tester to look for a leak.

Hope Greg's not right about potential head gasket issues. Engine seems to run strong and compression testing last Fall was great on all cylinders. I also don't recall having this problem before I installed the new rad although I'm not sure I was evaluating everything with this much precision. Unfortunately, I did a lot of mods this Spring at the same time as the rad -- I also installed a new allison's header and there are some coolant ports in the manifold area under the gasket. Wonder if a mainfold not properly secured could also cause this?

Hey Greg, have you checked ...

the coolant level in your reservoir? It needs to be 3/4 full. If it get's too low, the coolant line below will suck in air bubbles from the return feed hose above it and inject air into your system slow but sure.

To some degree, this happens anyway, but over a period of a few thousand miles.

Thanks Bob - checked my reservoir tank and it's ~80% full. However, I followed Tony's advice, stopped by my local autozone, and borrowed a pressure tester -- fits the stant connection perfectly.

Checked my cap -- rated at 13psi (although I understand stock was 11psi right?) and it's working properly.

Attached it to the system. Pumped it up to 20 PSI and seemed to hold pressure well.... and then found some drips under the vehicle in three places: Passenger side radiator hose connection to underside tube (will tighten clamp), under passenger side of radiator (where, uh, my new plug is -- I will tighten it), and at the hose connection to the water pump tube (which is connected to the thermostat housing -- will tighten that).

I'm guessing the water pump tube connection may be the culprit, because it is also surrounded by the header tubes and experiences A LOT of heat. I THINK the water pump is also "pulling" coolant from the left (passenger) side of the tube which I'm guessing makes it a potential area for air to get into the system. We'll see...

Anyhow -- more work to do. I'll try to tighten things up better, do some additional pressure testing, and try it again...

Greg... THOSE DRIPS are indeed your problem...

Good work!

BTW... many, many moons ago we posted stuff on what cap pressure should be rated at... and IMHO, usually the higher the better.

I believe the '74s had 7 pound caps and all others had some rated close to 12.8 psi in some other language. Stant's 13 pounder, preferably the lever-vent types, have worked well for me for the past 31 years on this car o' mine... as well as others I've messed with.

Fix those drips and RETEST to make sure... and I betcha the 20 bucks Bob owes me it fixes your sucking problem...

I don't like the sound of that...

Black-Tooth said:

Fix those drips and RETEST to make sure... and I betcha the 20 bucks Bob owes me it fixes your sucking problem...

Click to expand...

Ha! :boxing:

Tony owes Bob $20...

Black-Tooth said:

Fix those drips and RETEST to make sure... and I betcha the 20 bucks Bob owes me it fixes your sucking problem...

Click to expand...

*SIGH* I tightened several hose clamps. Not sure why I didn't check them earlier -- perhaps because I never saw any drips/puddles. Anyhow, with the tightened clamps and radiator plug the system holds firm at 25 psi. Before tightening them, I had a fast dripping section at pressures >15 psi where the rubber elbow connecting the water pump tube attaches to the thermostat housing. Went for a nice, long test drive last night, and.... More air in the system

I burped it twice. It's definitely pulling more air into the system and it happens while the engine is running (not after it sits). I've also sometimes picked up a faint whiff of burned coolant smell from the engine compartment (for example, when backing-up) so I closely inspected with the engine running and with it off. I can't see ANYTHING leaking. Engine seems to run very well with no loss of power, funny noises, misfires, etc -- I'm hardly an engine expert but can hear and feel when something BIG is not right...

I DID notice that I have some gunk/moisture near the exhaust ports/head on the driver-side of the engine. The middle and passenger sides are pretty clean -- see photos below. I'm going to wipe this area clean again and see if I get more schmutz there when driving -- if yes, I wonder if this has something to do with it???

Any ideas? I can post photos of other areas of the engine bay if it's helpful...

Driver-side (near piston 1) showing some gunk/residue -- was clean 350 miles ago:


Passenger-side (near piston 4) showing very clean still after 350 miles.

Greg, might be bad news...

you "might" have a head gasket leak.
It's possible that engine pressure is pushing into a coolant chamber when it's running.
I know this might not be what you'd like to hear, but...

Bob -- could be. Hope that's not it. Perhaps wishful thinking on my part, but I don't THINK this was happening last season. I changed the radiator, header, and (reattached) the water pump this Spring. Really hoping it has something to do with one of those...

Reply

Hi Greg. Well.....it's certainly possible that Bob may be correct. And that combustion gas is leaking into the cooling system through a faulty head gasket. Remember combustion gasses are at 150 psi or so. Would seem to POSSIBLY fit all your symptoms.

This should show up in a cylinder leakdown test. A tester is currently on sale at Harbour Freight (you got one near you ?) for $39 :
http://www.harborfreight.com/cylinder-leak-down-tester-94190.html
Poke around the web and you can download and print out a 20% off coupon. Brings it down to $32...

At this point it's probably worth it - at least for peace of mind.

By the way, apparantly the instructions supplied with the unit are incorrect. Just google it and lots of posts telling you how to use it correctly.

Good luck. Keep us posted. Doug

I agree with Bob.

Do a leak down test and see what's happening in the cylinder.

My 1500 suffered the problem of air in the cooling system and I thought it was just that I didn't bleed the system and/or had a leak. I didn't do a leak down test but wish I had. I took so long to figure out the problem (while still driving the car) that the head gasket started burping air out the coolant tank cap in a big way.

See this thread -

http://xwebforums.com/forum/index.php?threads/24571/

No major damage was done to my engine, fortunately. I'm waiting for the head to come back from the shop with a new cam, valves, and otherwise spiffed up (I'm upgrading a little while it's off). The block surface is undergoing a thorough cleaning & flat checking and will be ready when the head comes back.

One thing I learned from my machinist (who has many years working on X1/9s and things substantially more exotic than that) is that detonation will kill a head gasket quickly. He thinks that's what did in mine and suggests I'm fortunate that only the head gasket went. :nod:

Good luck with yours. Do the leak down test.

Yeah Greg... Time to purchase both a compression tester and...

a Leak-Down Tester at H.F.

Usually a compression test will show the problem and you can place your finger over the spark plug hole of an adjacent cylinder to feel air escaping. This problem you have may be much more subtle and a leak-down test should cause it to be seen.

Sorry for the bad news but its OBVIOUS you found and fixed all the other issues... and with as much air and as fast as the problem seems to occur... It unfortunately makes sense that there is some high pressure possibly being forced into the cooling system.

Yup...

As always, really appreciate all the advice and expertise here -- and I will follow it. Tried to get a loaner tool since I HOPE not to be doing a lot of leak-down tests in my future. But nobody loans 'em. Thank goodness they can be had from HF for fairly low $$$. Hope to get things tested this weekend or sometime next.