Head Gasket?

Follow Up

Here's a bit of follow up on this:

Compression test results looked good (125PSI on all cylinders). Leak Down Test indicated less than 10% leakage on all cylinders.
No Evidence of communication between Coolant & Lubrication systems.
The new coolant reservoir has been installed, system filled & 'burped'. (I didn't really expect that to cure anything, but it was necessary after the old tank ruptured).
The symptoms persist. Lots of bubbles in the coolant appear as RPM Rises, and the engine 'stumbles' if you try to rev it. It's worse if you open the throttle quickly - won't climb past 3,000RPM. If you open it slowly, it will climb to 4,000 RPM or so.
We though perhaps the ignition control module was failing, so we re-built it with the GM HEI Module, per Bob Brown's excellent instructions. I'm inclined to say it idles more smoothly after that, but the other symptoms persist. (Timing appears appropriate & stable.)
Then we thought we may have run afoul of a problem with the Thermostat-Housing/Head interface, allowing communication between the Cooling & Exhaust systems. We opened that up to find that the head on this (fuel injected) engine doesn't have the hole drilled through that surface into the exhaust ports. So, nothing there is going to change, once it's back together. (pics at end of this thread: http://xwebforums.com/forum/index.php?threads/30458/)

I appreciate all the suggestions so far, and am hoping for some more that can guide me to the root of this trouble. Please share your thoughts.

Brian
 
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Are the bubbles new?

I have no idea what the problem is, but this is what I keep thinking:

I know I have been distracted from the actual problem by things I just never noticed before. Are the bubbles new? I looked thru the thread and was wondering if you only noticed the bubbles because you were looking for a problem. My tank shows a lot of swirl and some foaminess when running just from the water pump doing its thing. Perhaps the bubbles were always there and you didn't notice previously when it was running well?

Maybe this is a fuel delivery issue? How about fuel pressure? The engine can't burn what it isn't receiving. Clogged filter or injectors? TPS thingy not working right? Air flap not flapping all the way?

I know I am probably not helping, but it was on my mind.
 
Oil and cooling systems seldom intersect on the sohc, it's not the usual for the oil to become like chocolate milk... when it does it more often than not points to a corrosion issue that causes the systems to mix, like the alloy screw in plugs under the cambox corroding and allowing coolant into the oil. It is not a usual symptom of head gasket issues on the sohc.

In your leakage test cylinder 1 has a much higher %age leakage than the others... when the engine is cold, pull the plugs ... perhaps cylinder one will seem a lot cleaner than the others. Then crank the engine with plugs out and look for signs of liquid being expelled when cranking from the plug holes.

Look back at Hussein's picture,cylinder 1 is to the right... above the cylinder in the pic is a large water jacket opening (above the waterpump on the block) and I've seen this leak cylinder pressure into the cooling system.

Your reservoir tank cracked...often indicative of combustion pressure finding it's way into the cooling system ... you must also have had a problem with the cap, as it should have vented excess pressure off.

A small stream of fine bubbles due to water agitation is common, but large bubbles - like a pot coming to the boil - indicates a problem.

SteveC
 
Thanks

Thanks for your thoughts, Jim.

I guess it's possible that it's always bubbled, and I never noticed... After all, why would I go peering into the coolant tank while revving the engine, before? But it does seem strange... Jury is still out on this one, in my mind.

We'll consult the L-Jet diagnostic manual the next time we can work on it. That's a good suggestion.
 
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Thanks

Thanks for your thoughts, Steve.

We'll take a close look at Cyl #1, as you suggest.

Yes, the ruptured tank & the bubbles in the coolant system have seemed connected, in my mind, too. (Then again, it could just be 35 yr old plastic that's been through many heat cycles, getting brittle.) It's quite possible the cap was not good. It's been replaced.

I wish I were able to post some video/audio to help define how many bubbles I'm classifying as 'a lot'. It might be helpful in describing the reluctance to revving, too... Maybe I can figure out how to do that...

Brian
 
video

I got a little help with making a video, to help with diagnostic suggestions. In true "repair tech syndrome" form, when we took the video to show the symptoms, it ran more smoothly than it has since the onset. But, the bubbles in the coolant are visible. Please take a look, and let me know what you think. Here's a link: https://youtu.be/wRZXXx0HTGo

Brian
 
Confirmation

Thanks for a confirmation with no shadow of doubt in your mind. I appreciate it.

Brian
 
Difficult to tell. Coolant drops in the tank might causing bubbles, like pooring coke from a heigth in a glass. Best fill the tank completely until the upper inlet is under the coolant level and then try it again but ref not to hard. Wait until you really see gass bubbles coming out.

Better is to replace the coolant with clean water. That doesn't foam by itself. Another way to identify which cylinder leaks, do a compression test for each cylinder and keep an eye on the coolant level. The level will rise on the cylinder that leaks gass to the coolant.
 
Trouble shooting 101

Brian,
The video helps. It looks like the coolant is foaming, not normal.

I understand how you might question the head gasket, but taking off the head to check the gasket isn't simple. For trouble shooting you want to check the simple things first. I think Dan is spot on. Do a simple combustion gases in the coolant test. That should give you a lot of information.

You didn't give us a lot of background. Was the engine running well before you pulled it into the garage? The tests you did point to a head gasket that's working as it should. But, you do seem to have foaming in the expansion tank. ??? The plastic coolant tanks crack even without blown head gaskets. The rad cap should limit pressure anyway. You may have some kind of red herring in the coolant tank breaking?

One thing that's unusual is that all of the sudden the car doesn't run well. You need to trouble shoot that before you pull the head.The biggest single influence on how the FI engine runs is the water temp sensor. It's not difficult to test, so check it before you take the head off. (Maybe you tweaked it when you changed the coolant tank???) Also, you didn't tell us where the air was leaking to when you did the leak down test. You should be able to see bubbles if it's leaking into the coolant when you do the test. If it's leaking past the rings, you'll hear hissing out of the oil fill cap. If it's leaking past the intake valve, you'll hear it out of the intake, the exhaust valve leaking should hiss out the muffler. BTW - #1 cylinder typically gets more cylinder/ring wear due to thermal shock.
 
In the same boat

I have changed lots of head gastkets in the past and here is what I notice.

Cold engine start it up, a bit of a rough idle. Take off the coolant pressure cap and there is a lot of pressure. Put the cap back on and rev the engine to 6000 RPM, now take the cap back off again. Is there a lot of pressure? In my case there is. Also what I noticed was when driving the car the temperature gauge goes to 190 degrees then a moment latter drops to 150 and the cycle starts over again. I have seen this a lot of times and I know it is the head gasket. I have a spare head I will send out and get machined first off before I pull this one then I won't get held up when I do the job.

TonyK.

Grimsby Ontario Canada.
 
More Follow Up

A little more follow up:

My father and I have limited time available to work on this, so progress has been slow. But we enjoy the time we have (mostly). The comments and suggestions shared have been beneficial, and Dad's mechanical intuition has been invaluable.

Testing the car, Dad's feel was that the stuttering problem was fuel related. So, we were working through the Jetronic diagnostic manual (as was suggested here). In the process, we found readings that were out of spec for the Coolant Temp Sensor, and (drumroll, please...) found that the Thermo/Time Switch was loose AND telling the cold-start injector to run when it shouldn't. With the switch disconnected (so the CS injector wasn't signaled to operate) the resistance to revving went away. Replacing the out-of-spec Coolant Temp Sensor can only help. With the switch tightened, I'm hoping the coolant bubbles will go away after more bleeding of the cooling system. A replacement coolant sensor & thermo/time switch are on their way. I'll update again, after they are installed & tested.

Thank you again, to all who have offered suggestions or asked clarifying questions.

Brian
 
I hope you're right, but...

I don't see how a loose or faulty thermo time switch will solve your air-in-the coolant problem although I suspect it likely WILL solve your acceleration problem.

I've been watching this thread with interest because I have a similar problem. Like you, I get considerable air in my coolant system. My tank bubbles like yours -- maybe a little less but similar.

Pressure tested coolant system to 20psi with no significant pressure loss and no coolant loss.
Did a compression test: Results were good on all cylinders.
Did did a leakdown test: Results were good on all but cylinder 2. http://xwebforums.org/showpost.php?p=209839&postcount=5
Pulled the plugs. No evidence of coolant in cylinder 2 (plugs were dirty).
Put high PSI (100) on cylinder 2. No air in the coolant tank. But some air out the exhaust?
Tested for exhaust gas in overflow tank. Nothing. http://xwebforums.org/showpost.php?p=212833&postcount=7

I eventually DID pull the head. Some speculation from forum members about potential issues but overall didn't look seriously bad. Installed a new head and tapped/sealed coolant ports on the manifold. http://xwebforums.com/forum/index.php?threads/26663/

Re-routed my water pump heater hoses (which were close to the manifold).

Still getting air... I'm concerned that my cheap HF leak-down tester is faulty -- or the tester (me) is faulty so I'm taking the X to a local trusted mechanic for additional compression, leakdown, and pressure testing.

Will let you know what I find. Looking fwd to learning from your experience.
 
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Handful of smoking guns

Glad you were able to reduce this to a few faulty / improperly installed components.

A comment on the thermo-time switch: Although it may have failed "closed" (I have seen three fail "open"), this should not affect running. This part of the circuit is only energized as long as the starter solenoid is energized during starting. It may be worth checking the wiring around the thermo - time switch to make sure there aren't other problems as well.
 
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