Sucking air???

Long distance diagnosis...

After my repair (head gasket in my Scorpion's twin cam) I drove 500 miles. Next morning I checked the coolant level in the ss tank. within 1" of the neck. I too found a single drip leak at a hose connection with a cooling system pressure tester. I too smelled coolant occasionally. After 1.5 hours of driving enough air would be in the system to cause problems.

It sure sounds like a head gasket leak similar to mine.
 
UPDATE: Cylinder #2???

OK, so I did my leak-down test with the HF tester. Pretty sure I did things right although I had to run the tests on each cylinder several times to be sure. In some cases, I'd calibrate the gauge and while running the test, the needle would swing very high/low -- after disconnecting the gauge was no longer calibrated. I threw out the results whenever that happened, recalibrated, and tested again.

So, for the tests that ran as expected and were reproduceable (i.e. I could calibrate the gauge, obtain a result, disconnect the hose and the gauge showed it was still calibrated for test)...

Cylinder 1 was good. VERY good. Hardly any leakage and well into the green. Just a nudge off the calibration position.
Cylinder 4. Ditto
Cylinder 3. Ditto
Cylinder 2. Moderate leakage reported. Did not see any bubbling into the reservoir tank. Not sure where the air was going. But the tester reported near 40% leakage or on the edge of moderate.

I also had to pull the plugs. See pics below. Cylinders 1,2,3,4 from left to right. The cylinder 1 plug was especially clean although it's not obvious from the photo. Cylinders 2 & 3 were more cruddy. Cylinder 2 is the darkest but not a lot more than the others.

Any recommendation on the prognosis? Do I pull the head based on cylinder 2? I really don't waaaaaaaaaaaaaaant to. But will do the job if that's the case...

 
I'd try to get a hold of a scope instrument to look inside the cylinders and see what the piston tops look like. If they look like mine did, super grungy with a steam-cleaned edge, then you'll have your answer. One question, did you listen at the tailpipe and air intake for air noise? I ask because you don't mention it. Either of these noises would mean a leaking valve.

I saw one at Home Depot today for about $180, Milwalkee brand. It's something I might look into getting because it would work for automotive stuff as well as my design/build profession. I can just imagine being able to drill a 3/8" hole in drywall and looking inside a space for mold or wires or what have you.

I tested for air leakage using my compressor set to about 125 psi to test for air leaking into the coolant, but didn't see any probably because of the system design, in that air would not readily show in the reservoir.
 
Good idea Greg! I have one of those cheap China cameras on the end of a usb cable and I think it will fit into the spark plug hole. It also has some LEDs on the front so I hope it will take good pics. I'm out of town for a week to help my stepdaughter move and will check it when I return!
 
Greg, yur gonna like what I have to say, for now, anyway...

I'm not an expert when it comes to a leak-down test... but we've come a long ways around looking for that coolant leak.

It just very well may be that head gasket... but let me say this after looking at your plugs.

Plugs that are firing with coolant in the cylinders tend to be very CLEAN as compared to the others. Yours appear darker... almost as run hotter or more oil fouled... which they are not.

I would first do as Jeff suggested and perform the tests again and verify if you can feel air out the 1) exhaust, 2) the intake, 3) the coolant reservoir, and 4) also the crankcase via the oil cap.

If there is NO air in the coolant system... I'd try re-installing the plugs and running about 1/3 quart of ATF into the intake over about 10 minutes. (An Italian Overhaul in a can...)

Then retest the cylinders and post the numbers here.

This should alleviate any engine issues... and we can then focus more on the coolant issues. But if there is air coming from the reservoir... its time to pull the head.
 
Reply

Hey Greg. Sorry for your troubles. But if your leakdown test is accurate, I really dont think you can ignore the elephant in the room - the 40% leakage in cylinder #2....

Yeah, I guess the leakage has gotta be going somewhere. Yes, could be past valves, rings, or.......through the head gasket into a coolant passage. Which would match your symptoms.....of air (or actually combustion gasses) getting into your coolant system.

Keep in mind that IF this is the case, I would think that gasses leaking INTO the coolant passages (combustion pressure is super high) would be FAR greater than coolant leaking into the combustion chamber (the coolant pressure is only 14 psi or so).

SO I kinda think you are wasting your time looking with a camera into the combustion chamber, or looking at the plugs. Concentrate instead on looking for gasses getting into the coolant...

When I googled the HF tester, a common complaint about it seemed to be that it only pressurized the combustion chamber to about 15 psi or so for testing. Most other leakdown testers use 80 to 100 psi. They are also way more expensive...Apparantly the reason the HF tester uses low pressure is that if you aren't exactly at TDC, pressurizing the combustion chamber at a high pressure will just move the piston down the bore. So to use a high pressure tester means you gotta lock the engine from turning somehow. At only 15 psi you dont have to bother, so the HF tester is easier to use. At least that is what some people say....

But at only 15 psi, where the air is leaking to is not so easy to determine. At 100 psi, its usually pretty obvious......

So if I were you, I'd try the leakdown test in cyl #2 again. Try your best to figure out where the air is leaking to.
Past the rings will end up in the crankcase - remove the oil cap and listen.
Past the intake valve will end up in the inlet tract - yank off a vacuum hose or something and listen.
Past the exhaust valve will end up in exhaust system - listen at the end of the tailpipe.
Into the coolant system can be tougher - due to the X's funky system with a sealed rad. Air tends to accumulate in the top of the rad more than into the coolant reservoir. So fill the coolant reservoir TO THE BRIM and watch for a rise in the coolant level (ie spillage out the top) more than air. Theory here being that air into the coolant would displace some coolant.

If you are still not sure where the leakdown is occuring, then set #2 to TDC as close as you can, lock the engine from turning (in gear with handbrake on should work) and figure out a way to hook up your compressor and fittings to give full air pressure (100 psi or so) into the combustion chamber. Then should be pretty clear where the leak is going.....

Good luck. Doug
 
Hmmmm... as this sites Spokesperson for HF Tools...

HA!

Well... the specs stated in their ad say its working pressures are 0 -100 PSI.

http://www.harborfreight.com/cylinder-leak-down-tester-94190.html

Whatdaya think? Have you used theirs? The HF unit seems to have more features than others selling at twice the price from Summit and others.

BTW, I also tend to agree with you also about using the scope... More fun than anything else in this case.
 
Out of town until next week so stalling my progress. The camera will be easy, quick, and fun so I will do that when I get back. I can also lock the cylinder in tdc and blast it with 100 psi fairly easily to track the leakage better. More coming...
 
Haven't had as much time as I'd like to diagnose this one, but finally got some time yesterday and today.



Put my endoscope camera into each of the cylinders. Photos weren't very good so I'm not posting them. However, I could use it to see most of piston tops in each cylinder. They were all very similar. Clean (but not steam cleaned) around the perimeter and some crud near the middle/center. None were particularly clean or dirty compared to the others. They all kinda looked like this:





I also put 100 psi on the leakiest cylinder (2). Air loss seemed to be coming from the exhaust manifold I also watched the coolant reservoir and did not see any bubbles or rise in the level when applying air to the cylinder.



So I'm stumped. I could pull the head but that would pretty much end my driving season (given the limited time I have to work on things right now).



Is that the consensus? Pull the head?



PS I also inspected under the exhaust manifold with the idea that perhaps it had become loose and exhaust gases were pushing their way into the coolant ports. I DID see a little schmutz on the underside of the manifold. I previously checked the mounting nuts and they seemed very tight. Wonder if this is relevant? I will probably wipe it and check again later...

 
Use a bubble solution around the manifolds

You can spray a soap solution around the exhaust manifolds while the 100 psi is in #2 and look for bubbles.

Commercially available solutions are available or you can use the stuff you let you children have to blow bubbles or even make your own from a mixture of water and a bit of dish washing soap.

Use a spray bottle to spray the area once you have the air pressure in the cylinder. If there's a leak, you'll see bubbles forming.

As far as pulling the head ending your driving season, how much more driving do you think you'll do this summer with the engine/cooling system in this condition? If it is the head gasket, driving will only make it worse.
 
Hey Greg...

The pic looks fine tome, no steam-cleaned edges like I saw upon teardown.

Have you tested your cap? A cap that doesn't hold pressure will allow steam to form at very hot places in the water jacket, and cause air bubbles.

Also look again for any leaks, including at various points of the new radiator.
 
Greg... I haven't read all this again but just a thought...

If you are sure #2 is on its compression stroke with both valves closed... and you are doing a leak-down test and feel/see air coming out the exhaust manifold... that would surely indicate a bad/burnt exhaust valve.

Retest all four to ascertain... and if so, time to pull the head.
 
UPDATE

I've done nearly everything EXCEPT pull the head, but I've nearly convinced myself that I will have to do that. I spoke with Matt Brannon (who -- BTW -- was REALLY helpful). He mentioned it is unusual for head gasket leaks to result in air in the radiator (vs at the water pump). He also said that head gasket leaks often result in overheating at high speed/load.

In my case, I can cruise 70MPH in 4th gear at ~4,000 RPMs for a LONG time (dozens of miles) and the heat guage is rock-steady. BUT when I hit stop and go traffic my fans will eventually kick-in late (nearly 3/4 up the temp gauge) and I never OVERheat in the red zone but the system struggles to get back to midpoint on the gauge until I am moving again. ...and I consistently get air in the radiator that need to be burped.

I drained my system. Re-checked all my fittings, inspected the coolant (and found NO oil/grease in it) and refilled it. I used Obert's recommendation for purging air from the system (with reservoir cap off). Couldn't see any air in the reservoir from 1-3K RPMs. But when I rev'd it to 6K and held it there for a minute or so the reservoir would froth a bit and start to overflow. It overflowed because air was building in the.... radiator.

SO... Consistent with the fdbk here, it seems I am zeroing-in on a head gasket issue but one that is not typical. It never overheats into the red zone and is rock steady when the car is moving (even with air in the radiator). Matt believes there might possibly be a small leak near cylinder 4 which releases air into the thermostat area where it travels up into the radiator (since it's not cavitating the water pump).

Off to Autozone tonight for a leak test kit loaner where I'll attempt to find exhaust gases in the reservoir. If yes, the head comes off when the X hits the garage for cold weather in late Oct or early Nov. If not, I will be further confused (and may still pull the head).
 
Sounds like Bobbrownitis to me...

He struggled for sometime with his A/C equipped Queen doing about the same thing. But not an air in the radiator issue...

I thought we were focusing on the engine and head and air coming out of the exhaust... and now yur thinking about the overheating issue and air in your radiator.

Hmmmmm....

If I haven't YELLED at you before, I haveta say I have yelled at others stating... If you are getting air IN the radiator then coolant is getting OUT somewhere.

In many cases, and just recently for me... its at HIGH pressure and gets out as STEAM with very little evidence of a leak as it EVAPORATES quickly.

I hadta pressurize my system to over 20 pounds to finally find a drip-drip-drip from a gooseneck on my 350 Chevy.

I suggest strongly that you do the same... Get the tester from AZ as well.

THEN... If you can't find anything and the pressure still drops... check the exhaust as well.

I'm THINKING you may have a compromise T-Stat housing gasket and the coolant is leaking out into the exhaust manifold. See here for more:

http://www.network54.com/Forum/12159/message/1133320021/

This hole still needs to be blocked on late model FI cars as well.

Its a STRETCH I know... but something to look into. HTH
 
I have a little seepage from my radiator, upper right core. Expansion tank eventually settles down to 1/3rd. At this point the seepage stops, I assume because the radiator is now mostly air. So in my case, coolant escapes very slowly, air gets in. Car runs a rock steady 185 but slowly warms to 190ish stuck in traffic, fans cycle, stabilizes there, when moving, slowly returns to 185. I need to fix my radiator. Even so, it cools itself remarkably well. Was stuck in a traffic jam yesterday for an hour and it did the above. I haven't noticed any frothing in my coolant tank but I don't look either. I've run it all summer like this, FWIW. So, yah, a little leak anywhere can do weird things. I agree: pressure test it.
 
Yup -- have done the pressure test and am fairly confident that's not my issue. When I previously pressure tested, I had a few drips at 20 psi due to loose clamps and a drain plug that wasn't sealing well. Tightened the clamps and re-did the plug and all is good at 20psi.

System is displacing coolant for sure but I think the amount is relatively small and the reservoir takes up the slack (level drops a little when I burp the radiator).

The exhaust gas tester result will hopefully shed add'l light on this. If no exhaust gas present I will start looking at the t-stat housing (per Tony's suggestion). It's tight and has a fresh/correct gasket on it but ya never know...

jvandyke said:
I have a little seepage from my radiator, upper right core. Expansion tank eventually settles down to 1/3rd. At this point the seepage stops, I assume because the radiator is now mostly air. So in my case, coolant escapes very slowly, air gets in. Car runs a rock steady 185 but slowly warms to 190ish stuck in traffic, fans cycle, stabilizes there, when moving, slowly returns to 185. I need to fix my radiator. Even so, it cools itself remarkably well. Was stuck in a traffic jam yesterday for an hour and it did the above. I haven't noticed any frothing in my coolant tank but I don't look either. I've run it all summer like this, FWIW. So, yah, a little leak anywhere can do weird things. I agree: pressure test it.
Click to expand...
 
I can't fault your efforts... but we do need to AGREE on one thing...

Coolant is being lost! Air is getting in... we just haven't found it yet.

A head gasket could do this as well... but again, you should see a pressure drop.

If you feel comfortable... take it to 25psi and walk away for 1/2 hour... see if that exposes anything.
 
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