Sucking air???

Cooling system pressure testing

In my case (recent Scorpion DOHC head gasket replacement) I pumped it up to about 25psi and waited for about 1/2 hour. Over that time it dropped to around 15 psi. The first run I found a leak at a hose clamp, tightened it, as it was loose, and that leak went away with no others apparent.

On the second pass, it did nearly the same thing with no external leaks apparent. This lead me to think the tester was faulty, as a leak-down test of each cylinder revealed no leaks. But in hindsight I think it was leaking a bit into the cylinders and I just couldn't see it.

In my case the coolant wasn't leaking out*, combustion/compression air was leaking in, causing air bubbles and resultant increasing funny temps as you describe. It takes very little air in the radiator to screw it up.

*Eventually I saw that while coolant wasn't leaking out much, when hot and parked after a run some coolant must've been leaking into the cylinders to cause the clean edges I saw on teardown.

And some rough running at startup, an eventually a coolant smell on startup as well. Only once did I notice any steam cloud from the exhaust and it was brief and right before I decided to change the head gasket.

If you can hang onto the coolant system pressure tester for another test, try this one (I just thought of it, should have done it myself): With a cold engine install the tester. Run engine and see how quickly the pressure comes up. If it's immediate, it would suggest a combustion air leak into the cooling system. If it's slow like one would expect from the coolant warming up, then that would be normal.

Header flange pipe expanding when hot loosening the intake manifold allowing coolant to escape. My best guess

Exactly what I fear as well Greg(s)... (pun intended)

Does, (Do) the spark plugs, especially number 2 and/or 3... look any different (washed?) that numbers 1 and 4?

First attempt...

OK I attempted my first exhaust gas leak test in the tank with the autozone tester and fluid. Result was negative: No exhaust gas detected in the coolant. I suspect I may have to run this test with the engine running for a longer period at high RPMs. To do that I will need to significantly lower the coolant level. Will try that again later. Here's the video so you can see how I did it:

[ame]www.youtube.com/watch?v=LHjr5FRzxmw[/ame]

...and here is how Scotty Kilmer does it. This guy's instructional videos are good (and IMO entertaining)
[ame="http://www.youtube.com/watch?v=QA7KVQq9vKA"]How To Tell If Your Head Gasket Is Blown - YouTube[/ame]

Problem is obvious. You can't use a stainless tank with your car, I will grudgingly swap it for my plastic one if you insist.

OK I think the mystery may be solved. I re-ran my test like I did in the video but left the Tester on the tank for nearly two minutes which is the recommended time for sampling. No change to the fluid.


I ran the test again and kept the throttle open such that the rpms were between 4 and 5K. Kept it going for nearly 45 seconds or so, at which time my neighbor stopped by to tell me that my engine noise was a problem... After apologizing to the unhappy neighbor I took a look at my test fluid and found the 45 second high rpm test had changed it. Wasn't fully yellow but well on its way and probably would have been fully yellow in another 30 seconds or so. Looks like I have a very small leak at higher rpms.

I think yur right but to be sure...

Run the same test again on one of your other cars... and again on the Fiat.

Talk to your neighbor first and tell him that you have been chasing this problem for a month and it should be over soon. If he still has a problem... tell him to call the cops and go have sex with himself until they arrive.

It does indeed look as if you are getting somewhere finally... and I have never heard of this tool before. Always learnin'...

When yur done... you might wanna call Scotty Kilmer and let him know you appreciate his help and what you found. He should be able to confirm your findings as well. And if the cops give ya any crap, tell then its your constitutional right to have ONE phone call.

Getting ready for winter projects and thought I'd pull the head. I just removed the rear access panel and found a small puddle of coolant at the base of the block. Looks like it has dripped from the base of the header flange.

Could this be the smoking gun? Wondering if this is where my air leak is coming from? I want to say "yes" but those coolant ports are on the intake port areas and not the exhaust port areas. I will remove the intake and exhaust manifolds to see what else I find...

Greg, you're doing the right thing

This is the ONLY way to know without doubt about your radiator air leak issue.

The key here is to be thorough. Clean everything\. Inspect the flatness of the head and block, particularly between and around the cylinders before you re-assemble.

Pick up A MWB recommended gasket while you're at it.

Let us know what you find, in particular when you remove the original gasket.

Good luck!

WAIT A MINUTE HERE, SANTA! Are you just wanting...

to pull the head... or find the leak?

1. Pressurize your system to 25 lbs and see what's leaking and where FIRST! Be patient it may take a while to start leaking in this case. Pull the plugs and see if you can FEEL any pressure building on your fingertips.

2. Always remember that if air is getting IN, then coolant is getting OUT... somewhere!

3. If you dirtied up that engine a bit with some grease and grime and dust and pebbles... ya probably could enjoy driving it for the next ten years with no problems!

BUT... don't let me spoil your fun. I guess if I hadta sit and just look at the car for 6 months at a time I probably would feel the same way you do after seeing this smudge.

HA!

Merry Christmas Greg!

your intake is leaking....

if it's coming from the header flange- don't take the head off yet- intake and exhaust share the same gasket...I had this problem, found that the face of the header had a layer of rust from when it was laying around before using, which kept the intake from getting good seal, since they share the same bolts...i took sandpaper glued to a piece of glass, and planed off the layer of corrosion on the header, just a thought

Hey Tony -- Good advice and I followed it a few months ago. I pressurized my system and found some loose hose clamps etc. Took care of them and no more leaks under pressure. So I either had a leak at the header/intake gasket during pressure testing and missed it or it wasn't visible at the time. I suspect I missed it because it didn't result in dripping on the floor.

...and I put over a 1,000 miles on her this summer and about 2,500 in the past two years ago. Hoping to double that next year (but still keep things tidy)

Kevin: Was wondering the same as you. I could only find a small amt of exhaust gas in my coolant when revving in the 4-5K range for several minutes. So I suppose it's possible that the exhaust gases were building at high RPMs and traveling behind the (loose) gasket into the intake area and coolant ports.

More analysis left to do...

Update: Still getting air :-(

OK I'm back again with this issue. I've pulled the head (and, uh, as long as I was at it I replaced it with a MWB perf head). Checked the head flatness and quite frankly the old gasket looked pretty darn good when I removed it.

I carefully followed Matt's suggestions about installing the new head, things were flat and clean and torqued in sequence and then re-torqued. Everything is running GREAT now. But I'm still getting air in the radiator.

I've pressure tested the system. I look for coolant drips under the car -- none. I've tapped and plugged the manifold cooling ports in the head. I've checked for fit of the manifolds -- they are snug. No vac leaks on the intake.

I think I will do something I've previously avoided. I'm going to reinstall the OEM radiator. This problem began after I performed two "upgrades" last year: An Allison header and a BobG radiator. Prior to that I did not have air problems and the OEM radiator was working fine.. Feels like I've chased nearly every other issue and dropping the radiator isn't that difficult. Furthermore I may have forced the decision on myself because the radiator bleed screw (or radiator bleed port) threads are stripped :-(. Probably because I've been burping it so often these past two years.

Greg... you're baaaaaaack! Same problem?

Does the pressure tester HOLD its readings?

If not... the you are pushing out coolant somewhere and air is entering.

If you keep getting air in the system then coolant must be leaving.

Make sure the pressure tester is sealed as well and make-up a soapy solution or buy a bubble-blower from the Dollar Store and soap things looking for bubbles.

Still loosing pressure? Pull the spark plugs or just loosen them and soap them. In other words find a way to SEE what is going on.

Sorry for your trouble here again!

I read the part also where the bleeder is toast as well... So that will need to be fixed or replaced.

Lastly... I use a flush TEE and hose pressure to back fill and force water and coolant through the system and heater core. I install them at the factory coupling near the cam cover in the heater hose.

Remove the cap off the reservoir and run the engine... run the hose as well and back fill and or flush it all out the top of the reservoir.

http://shconline-com.3dcartstores.com/Prestone-Flush-amp-Fill-Kit_p_2383962.html

Here is an example... they are cheap and will add THREE more possibilities for a leak but mine has been fine for 15 years. I have seen some shops just selling the TEE and CAP for a $1.00. You supply the clamps.

Works for me, but I am special... HTH!

Air in the system...

Your main complaint is air in the cooling system. This is usually the result of a leak that lets coolant out under heat and pressure, and allows air to suck back in during cool down.

It's entirely possible however that you could get air sucked in a place during cool down that doesn't leak coolant out or where the coolant evaporates, like a hot radiator or other hot area. I think going back to the mods performed prior to the symptoms appearing is a good idea, perhaps you'll find the problem. Certainly stripped bleeder screw threads would allow air in. Good luck.

Completely agree with you Greg. This is perplexing since it seems like there are only two ways for air to get into the radiator:

1. Air is injected into coolant passages from the head (e.g. gasket failure or some other area).
2. Air is sucked into the system somewhere during cooldown.

I'm fairly certain it's not #2, because the situation worsens as I drive. I don't find more air in the system the next day after a cooling cycle. I find more air in the system after a long drive. ...and whenever I park after a long drive I look under the car for drips etc. Don't find any. Also passed a pressure test at 20psi when I first started looking into this.

If I consider #1, I've looked at the head & gasket. I performed an exhaust gas test in the reservoir. I had to rev the engine very high (like 4-5K high) for a few minutes to get a very minor exhaust gas detection in the reservoir. So I pulled the head -- and the gasket looked pretty good. Checked the block, cleaned things up, installed a new gasket, torqued and retorqued the head, and no change. I spoke with Matt about this several months ago and he questioned how air could get into the system at the head, travel through the coolant lines underneath, and get trapped at the top of the radiator. Certainly not impossible but rather odd.

So I'm rather baffled. All I know is I had no issues with the original dented and half-rusted IAP header and the original OEM radiator (which seemed to be in good shape). Will be interesting to see if anything improves when I swap the radiator but quite frankly that would make me happy but even more confused...

What about the exhaust gasket? Does the header use a standard combined gasket, and could there be a flaw there?

might sound silly

if and when you pressurize the system do you hear a hissing sound?
I have seen hoses and connections that have a small hole, not enough to leak as a drip, but enough to leak pressure. steam escapes... fluid gone.
and are you talking about the purge nut (Allen)screw at the top of the radiator??
if not, jack the front up as far as you can and remove it. heater valve open, and put a garden hose in the overflow tank. run that for a few minutes till no bubbles.
lock it all down and hopefully no more problems.
if coolant is in the equation , raise the rear of the car and add as gravity takes hold while the bleeder is open.
hopes this helps
mikemo

There is also a vent/valve in the underside of the water pump (on my AC equipped version). I know this, 'cos when using Evans Waterless it has to be filled with silicone to prevent air being sucked in....

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Less than $25.

Dye:
[ame="http://www.amazon.com/Interdynamics-375CS-Radiator-Coolant-Dye/dp/B002M4E0VC"]Amazon.com: Interdynamics 375CS Radiator/Coolant Dye - 1 oz. Bottle: Automotive[/ame]

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[ame="http://www.amazon.com/Interdynamics-438-True-Light-Glasses/dp/B003JOB594/ref=pd_sim_263_2?ie=UTF8&refRID=16MAWRXM6K838CCDFD17"]Amazon.com: Interdynamics 438 True UV Light Kit with Glasses: Automotive[/ame]