91 civic - tough question about cooling

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first i'd like to say thanks to the great people on this forum for all the help they provide.
i've done a search for my problem and i've found some things but
nothing exactly fits.
i recently performed a head gasket job on my civic. i began this job because i had bubbling in my coolant resevoir after driving for a while. i also had some electrical issues, but i don't see those as related to the bubbles. the bubbling was not boiling. some kind of gas was pushing through to the resevoir, and i assumed it was compressed gases of some kind coming from the cyclinders through the head gasket.
after removing the head, i took it to the shop. they told me the head had to be machined by 6 thousands to remove the warp, which seems like quite a bit. he also pointed out where the likely breaches of the old gasket were.
i cleaned and lapped the surface of the block. there was no apparent cracking or warping (i checked for warp with a quality straight edge in multiple directions).
put everything back together to spec.
i filled up the cooling system, on an incline with the radiator high. bled the system according to haynes.
i've been test driving it for several days, and what happens is a little weird. after a light drive, i get a few minutes of bubbles (again, not boiling - bubbles) and i can hear coolant sucking past the rad cap in pulses. after a heavy drive i get the coolant pulsing, but much more bubbling - like the bubbling i used to get.
the only thing i have found that i didn't do was crank on the heater when i was filling the cooling system. is it possible that since i did not do this, there was a chunk of air in the heater core that is now escaping when the car heats up? i ran the car tonight at idle with the heater on full blast after discovering this possibility, but the rad stayed full (again on an incline) even with the bleeder open.
it seems there are three or four possibilities: 1 - block is cracked 2 - head is cracked and crack missed by shop 3 - heater core had air bubble and now air is working out 4 - head gasket was installed improperly
any thoughts? thanks.
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snipped-for-privacy@gmail.com wrote:

how exactly did you do this?

the head could be cracked, but honda aren't renowned for this kind of problem. much more likely imo, is that the cleaning/machining/lapping process has left marks in the head surface that make it impossible for a gas seal to be made.
either way, i think chasing down the problem is a bit academic at this point. the cost of diagnostics on the head to see if it really is cracked, labor, etc. just doesn't compare favorably with getting a "new" jdm engine from japan for $290 plus shipping. if the motor was rare and much more expensive, sure, chase the problem down, but it's not, so at this point, i'd just swap it out and be done with it. [replacement also eliminates the longevity issues associated with all the crud that inevitably gets into the engine when the head comes off.]
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i scraped the block surface with a plastic scraper at first. then i used carb cleaner and a toothbrush to scrub off the remaining gasket crud. after it was fairly clean i used 600 grit sandpaper tightly stapled to an index card sized piece of flat particle board. i lightly sanded the surface.

the head surface seemed near perfect after being machined. there were no scrapes/scratches of much significance on the block that i could tell, but who knows. what do you mean by "impossible for a gas seal to be made?"

if this becomes the route i decide to take, where do you recommend purchasing a "new jdm engine" (what does jdm mean - i thought the engine code was DB-13 or something).
thanks!
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snipped-for-privacy@gmail.com wrote:

ok. unfortunately, the backing block you need for this kind of operation needs to relatively large, very flat, and as rigid as possible. last time i did this, i used a 6" x 8" chunk of 20mm glass i got for free from a glass shop - it was in their scrap bin. much less and small local distortion of the backing block means you can get excess material removed from the "thin" sections, i.e. between pistons, and almost nothing from the thick sections. unfortunately, the thin bits are the worst possible place to remove excess as they're needed for sealing.

original surface on these things is near mirror. that way, there's no small grooves for gas to leak along. if the head was machined on a traditional milling machine, particularly this alloy head, it's /very/ hard to do without leaving scoring marks in it. last time i had to lap a head was to cut out the grooves from a bad machining job where the cutting die was picking up excess material on each pass of an exterior edge, then dragging that chunk across the rest of the head leaving gouge marks.

"jdm" is "japanese domestic market". due to tax and emissions laws in japan, cars usually get junked with only 60k miles on them. that makes them great for import to the u.s. where these engines still have loads of useful life.
there's loads of places on the net advertising these kinds of motors, and i don't endorse any particular one, but something like the site below is worth investigation:
http://home.pacbell.net/timwang1/38021.html

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snipped-for-privacy@gmail.com wrote in

You did this before or AFTER the head was machined to flatten it? Why would old gasket material need to be removed after machining to flatten it? It should not BE there after machining. Besides,I believe you do NOT want the mating surfaces to be polished(there's no need for it) because it would reduce sealing to the gasket.

The head would not clamp down on the GASKET sufficiently if polished or polishing affected the levelness recreated by the machining.
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Jim Yanik
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Jim Yanik wrote:

sealing is much more effective with a /smooth/ surface. look at the mating surfaces on high pressure valves and artillery. you're right if "polishing" makes the surface deviate from completely flat, but the flatter & smoother the better.
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just to clarify, i didn't polish the head, i polished the block. i never touched the head after it was machined.
small update: i drove the car to work today which ends up being about 70 miles round trip. at the end of my trip home (which is about a 2500 foot climb into some mountains), i park the car, turn off the motor and i hear silence for a time. which if i haven't been clear, is sort of normal but sometimes i would have a little bubbling after parking and turning off the motor.
it was clear though that this time there was no bubbling, even after a hard drive. however, after about 10 or 15 seconds i start hearing the slurping of the coolant past the rad cap. then the bubbling started. so, *no* bubbling with engine running, and *bubbling* shortly after the enginie is shut off.
i pulled the overflow tube out of the resevoir and noticed coolant coming out in small quantities in time with the slurping sound. is it possible that the recently shut down engine heats up slightly (i think they do after shut down), thereby heating up coolant in the engine, pushing coolant past the rad cap, but the flow is momentary (the slurping) creating a small steam pocket in the overflow tube, which then is manifested as bubbles in the overflow resevoir?
the rad cap is newish (~6 months old), but i have at least two other ones that i may test to see if they perform differently.
i am now hopeful that the engine is okay since bubbling isn't ocurring during engine operation.
thanks so much for all your input.
josh
jim beam wrote:

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snipped-for-privacy@gmail.com wrote:

there's only one situation where bubbling in the expansion reservoir is "ok", and that's the first time after the coolant's been refilled. that's the "burp". after that, all the air in the system should be expelled as it rises to the top of the rad and expands out as the system warms up. [it won't do it if there's too much air in the system, but i'm assuming everything was refilled ok.]
if the gasket/head/motor is still leaking, what you'll then find is that excess fluid gets pushed out to the expansion reservoir, and it stays there as the motor cools overnight. if there's an air gap under the radiator cap in the morning, it's either a radiator/hose leak, /or/ its gas from an engine leak having over-filled the system.
at this stage, you have to leave it to do its thing undisturbed overnight after it's been running to full temp. if you want to spend a little more money, there's a hydrocarbon test you can do on the coolant to see if exhaust is leaking into it, but i'm not sure how much that is offhand.

i have my fingers crossed for you. i've just been through all this myself, and mine wouldn't bubble while i watched it. gunning it up a big multi-mile hill at 105 degrees sure did the job though. it would blow coolant, then not suck back to refill completely. having changed /all/ the hoses and the rad and the water pump, there was only one other thing, the gasket. and as if to confirm, the last time i looked under the hood just before performing surgery, sure enough, there was a steady stream on bubbles blowing into the expansion reservoir.
good luck.

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snipped-for-privacy@gmail.com wrote:

--------------------------------
Here's another tip: You can't really overfill the reservoir with coolant. Any air the system displaces will just bubble out since it's not a sealed (pressurized) reservoir. Check it every morning when the system is stone cold. Make sure it's at MAX. Check it next morning, refill to MAX. Once ALL the air is out it will stop 'sipping' from the reservoir. That will tell you how 'healthy' the cooling system is.
'Curly'
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Not when you're compressing a head gasket,not all the time. With a metallic gasket,you WANT a texture to grip the gasket. *The gasket is what does the sealing.*

Which do not use gaskets. They are -mating- surfaces.

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Jim Yanik
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Jim Yanik wrote:

with respect, you're stuck in detroit there jim. "grip" on a gasket is simply grooving along which gas can escape - you really don't want it. that's why your old ford blew gaskets every 60k and a honda [typically] will go hundreds without being touched. i promise you, oem spec honda heads are near mirror finish, and that's for good reason.

they'd use them if they could! gaskets are single/low-cycle use.

there's /two/ mating surfaces when a gasket is used, e.g., block to gasket, gasket to head. /both/ need to seal, not just one.

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I'm solidly with the "smooth surface" view on this, but the question as it relates to this thread is whether the head gasket is leaking or not. I suspect not, but the OP really needs to check it out.
Mike
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Michael Pardee wrote:

yeah, if the head was done right, it's not the gasket, or at least, not this quickly. more likely it's a crack. that's pretty unusual for a honda, especially this vintage when their q.c. was really at its peak.
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The extreme smooth surface may not provide enough bite to hold the gasket securely. Too rough can also be hard on the gasket itself or even won't seal properly and the head gasket will leak. One way to judge surface finishes is with a comparator gauge and follow the manufacturer's surface requirements.
Laminated steel or rubber coated type of head gasket would require an almost polished surface finish. But most older milling and grinding equipment have spindle and bearings in weren't designed to meet these requirements.
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Burt wrote:

ok, question: where do you get this information? both you and jim clearly heard it from somewhere. what's the source?
there is no lateral load. no "bite" is required.

precisely. think about it logically: big grooves leak a lot. small ones leak less. a smooth surface leaks not at all. make sense???

and with a honda, that's a near-mirror finish!

no joking. that's one of the reasons why machining honda heads is such a hit and miss operation.
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Try using a single-blade cutter, instead of the two-bladed cutter. This is slower but yields a cleaner cut.
If they're caused by deposits, try removing the hard calcium deposits around the water jacket openings. The deposits can be picked up by the tooling and drug across the surface leaving a groove.
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Burt wrote:

it shouldn't be machined at all [or at least, not with "traditional" gear] for the reasons stated. it just needs to be lapped on a properly flat rigid bed.
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snipped-for-privacy@gmail.com wrote:

-------------------------------------
Keep this in perspective. When the engine gets hot it will force out some air (if there is air in the system). If there's enough coolant in the reservoir, (and the rad cap is working correctly), it will suck that coolant into the engine when it all cools down. The owner's manual is very clear: Whenever you have work done on the cooling system, you have to be sure to fill the reservoir to the MAX mark.
Are you keeping the reservoir full enough so the expelled air can get replaced with coolant? Once the air is all out, the system works 'transparently', but you still have to check it regularly, since some coolant can escape thru the water pump weep hole. Service manual says it's acceptable.
'Curly'
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i can't imagine that, despite my crude backer, my 600 grit sanding removed enough material to make a significant difference in the mating of the surfaces. i am a metal fabricator and i am sure i removed less than .0005 or less total. if a gasket can't make that up... the gasket itself was, say, about 1/16" thick or greater. are they not designed to take up some slack in the mating surfaces?
the head was done at a shop that pretty much only does that, particularly for dealerships. it was perfect.
the heater core hasn't been addressed. could my mistake of not turning up the heat while filling the system leave a large air pocket in the system?
thanks. this forum is easily the best!
'Curly Q. Links' wrote:

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snipped-for-privacy@gmail.com wrote:

not really. original honda head/block surfaces are mirror smooth and dead flat - no "slack" to take up.

ok. that makes a crack more likely.

that'll make it burp, not bubble. bubbling is a dead giveaway, especially in a honda where the leakage channel is straight into the water jacket.

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