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Tiny Bubbles in my coolant ... cooling system pressurizing
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91 Isuzu 4ex1
Novice
Oct 6, 2012, 7:34 PM
Post #1 of 10
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Tiny Bubbles in my coolant ... cooling system pressurizing
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Hi All,
First post here. Have this nagging issue with our import, a 1991 Isuzu Stylus S with 1.6 SOHC 4-cylinder.
Originally I thought I was simply replacing a leaking head gasket due to coolant and oil leaks around #4 cylinder.
Removed the head and sent it to the shop for cleaning, checking and milling (shop replaced valve seals and cam seal from HG kit). Put it all back together and it burned 2 quarts of oil in 300 miles. Pulled it apart and removed and replaced the rings, honed the cylinders and re-installed the pistons.
After replacing the head a second time it was still burning oil, and now there was a lot of heat coming from the cooling system.
Removed the valve seals installed by the shop with new ones. Stopped burning oil. Noticed that pressurizing #4 while replacing the seals also pressurized the cooling system enough to force coolant out through the cap and hoses. Cylinders 3, 2 and 1 no problem.
Cars runs OK, 200 lb compression on all 4 cylinders. Oil level is good, but oil is getting black faster than I would expect. Coolant may be entering the engine when running (probably #4?), but no white smoke, no external leaks and no coolant in the oil. If the coolant is 'evaporating' (humor) or being burned it isn't very much, almost imperceptible. NOTE: Car just passed its e-test with flying colors.
I tried Irontite All Season sealant and that helped a little, but the engine is still pressurizing the cooling system. Coolant enters the recovery tank only when cold and the cap is released. BUT, coolant will not re-enter the rad from the recovery tank when cold.
I've built a number of engines (mostly NA 6 and 8 cylinders) and never had this much trouble before sealing an engine or installing head gaskets.
Question:
What am I missing? a) head gasket (AGAIN??) b) cylinder head? or c) block?
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re-tired
Veteran
/ Moderator
Oct 6, 2012, 8:27 PM
Post #2 of 10
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Re: Tiny Bubbles in my coolant ... cooling system pressurizing
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Sounds like you have a bad head . Take the intake mainifold off and static fill cvooling system (not running) Pressurize one cyl at a time, spray a soapy solutuion into head via intake ports watch for fizz. The machine shop may have missed a hairline crack.
LIFE'S SHORT GO FISH
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91 Isuzu 4ex1
Novice
Oct 6, 2012, 9:00 PM
Post #3 of 10
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Re: Tiny Bubbles in my coolant ... cooling system pressurizing
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Thanks for the reply. Really appreciate it.
Was leaning toward a cylinder head problem when I arrived at the forum, primarily because the cooling system:
- Slowly pressurized only on #4 when doing the valve seals
- Pressurized immediately when the engine started from cold
- And coolant did not return to the cooling system when cold
I've been 'chasing' two separate issues - burning oil and anti freeze residue (a very small amount) in the exhaust that I'd never seen before in 45 years of tinkering with cars. I was beginning to doubt myself as well as the work done by others. Assumed (there's that word!) that the shop checked the head properly. The shop knew that car had over 200,000 KMs on it when I tore it down.
As I tried to figure out where this re-build had gone bad, I began looking at what I had and tried to eliminate the things that it couldn't be. I knew it would have to be one of three things: the block, the HG or the head. Since I had good compression on all cylinders it appeared that the HG was fine, and once the valve seals were replaced (twice) it stopped burning oil. At that point I figured that I could be faced with a bad block or head. That's when I tried Irontite to see if it would seal the crack, and it sort of worked, exhaust was not laden with any anti freeze moisture (funny, no white smoke though).
Since my garage is somewhat limited, and some of the repairs I have done (although inexpensive to this point) have been by process of elimination (sensors for emissions as an example), I can only approach this last niggling problem by pulling the head (AGAIN) and replacing it with a known good one. If my garage was ready with air and such so I could do this as recommended I certainly would. I truly believe that doing it as recommended is the right thing to do, but without air it won't happen. And as I explained, we just moved and the compressor is over in a corner; - the garage needs to be wired, well you know the drill and now I'm whining, so I'll stop.
When I take the head off, should I be able to see evidence of a crack from the water jacket to the interior of the cylinder, and what might it look like?
The head and the intake have to go on together because of the way the common chamber wraps around the head. There's not a lot of room to get at the bolts that attach the intake to the head from behind; - everything, including the intake runner and common chamber makes getting at the bolts while the head is still on the car a nightmare.
If it makes sense, I'll obtain a new head and swap it with the original and put it back together and see what happens. I'd take it somewhere and have it done, but my labor is cheap and money is also an issue or the garage would be better equipped to do this. New head is about $200+ shipping and core on eBay.
Thoughts?
(edited for clarity, not wishing to be argumentative)
(This post was edited by 91 Isuzu 4ex1 on Oct 7, 2012, 6:33 AM)
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Hammer Time
Ultimate Carjunky
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Oct 7, 2012, 6:36 AM
Post #4 of 10
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Re: Tiny Bubbles in my coolant ... cooling system pressurizing
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I never saw any mention of overheating or coolant consumption here. That would be the main symptom of a compression leak to the cooling system. It wouldn't have anything to do with oil consumption.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Oct 7, 2012, 6:38 AM)
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91 Isuzu 4ex1
Novice
Oct 7, 2012, 7:41 AM
Post #5 of 10
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Re: Tiny Bubbles in my coolant ... cooling system pressurizing
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Good points.
It was burning oil right after the head was originally replaced, 2 quarts in the first 300 miles. The theory at the machine shop was that now that the top end was sealed, the rings were in need of replacement. Once the rings seated it still puffed oil (and moisture) on start-up (valve seals) at the tailpipe and appeared to be running rich. So I wrestled that one to the ground, finally replacing not only the rings, but later the valve seals, valve seals in a head that my hands had not touched up until that point.
Before I added the coolant sealer it had a 'hint' of anti freeze or moisture coming out the exhaust, but it was so little that it didn't create any white smoke. What was coming out the back was predominantly blue smoke. The blue smoke was present at start up, and during the break-in period (about 1500 miles) while the rings seated. But it never completely stopped, until I replaced the valve seals.
The ECM and emissions are so 'caveman' that it is pre-OBDI and no one has a cable or diagnostic software to read the ECM in real time. Saturn SAAB Isuzu where we bought the car in 1991 used to have these tools, but when the brand disappeared the tools went with it. Actually that isn't completely true, the Lotus Elan group of people have cables and diagnostic software but I got the impression they thought the Isuzu Stylus was not even close to their 'breed' even though the engines (and likely the electrical systems) all come from GM Lotus and Isuzu development. But this is another topic, and I digress.
The coolant issue manifested as excessive heat when the car was running. Ordinarily the cooling fans never come on, particularly when the ambient temperature is below 50 deg F. The fans will come on anytime the AC is activated however. Plus, the cooling system now began pressurizing at start-up. It also had small champagne bubbles. Adding the coolant sealer reduced the excess heat issue, but the cooling system was still pressurizing during run.
I kept watching the recovery tank to see if the fluid went down, but it didn't appear to measurably, and standing behind the vehicle didn't give any indication of an anti freeze smell, or residue. As a bonus however, now that the valve seals have finally been replaced with new ones, it stopped puffing oil. Almost there, I guess.
If you were a betting man, would you equally weigh the head and the block as a root cause, or lean toward one over the other and why?
What else might help isolate it as one over the other (since I can't do the recommended diagnosis for the reasons stated earlier).
I don't want to jump straight to a solution, but it looks like that is where I am.
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Hammer Time
Ultimate Carjunky
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Oct 7, 2012, 8:08 AM
Post #6 of 10
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Re: Tiny Bubbles in my coolant ... cooling system pressurizing
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That was a very long post of pretty much useless information.
You don't have any coolant loss........
You don't have extreme overheating........
Your testing is flawed and I seriously doubt you have any head or head gasket issue but you sure will have a cooling problem if you continue to try to fix a non-existing problem by filling the system with sealer.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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91 Isuzu 4ex1
Novice
Oct 7, 2012, 8:44 AM
Post #7 of 10
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Re: Tiny Bubbles in my coolant ... cooling system pressurizing
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Thanks for the replies.
I'll end here.
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Discretesignals
Ultimate Carjunky
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Oct 7, 2012, 10:39 AM
Post #8 of 10
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Re: Tiny Bubbles in my coolant ... cooling system pressurizing
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I believe that if you pressurize a cylinder with compressed air from your air compressor and you see bubbles forming in the coolant that is a sign you have a sealing issue. Wether it is due to a poorly sealing head gasket, cracks in the head, or cracks in the cylinder bore, the head has to come off and the cause determined.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Oct 7, 2012, 10:43 AM)
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re-tired
Veteran
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Oct 7, 2012, 12:43 PM
Post #9 of 10
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Re: Tiny Bubbles in my coolant ... cooling system pressurizing
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My point ezacly.
LIFE'S SHORT GO FISH
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Hammer Time
Ultimate Carjunky
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Oct 7, 2012, 2:18 PM
Post #10 of 10
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Re: Tiny Bubbles in my coolant ... cooling system pressurizing
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If you have compression leaking into the coolant system that severely, you will superheat the coolant with combustion gases and overheat in real short order which this car is not doing. You will also fill the cylinder with coolant on shutdown, if not all the time and this car is experiencing none of that so I really doubt the test findings here. I've never seen a head gasket open between combustion and water jacket that didn't overheat or consume coolant.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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