OK, my wife's '93 Civic has been having a coolant issue lately. After driving for a little while (engine warms to operating temp) the coolant overflow will fill to the top and after cooling down, it will not go back into the radiator. Doing this enough times will result in the coolant level lowering and then causing temp to rise.

all have about 5k miles on them:
head gasket
OEM 1.1 bar radiator cap
dual core radiator
coolant

I ran the engine with the cap removed and did not see any bubbling like exhaust/ cylinder compression was entering the coolant system. I have since changed the radiator cap with another (older) OEM 1.1 bar cap, ran the engine to operating temp and didn't see the coolant fill the overflow. Right now, I'm waiting for it to cool so i can check the level. No visible leaks from any hoses or heater core. No smoke from tailpipe, no oil in coolant, no coolant in oil.

Still wanted to rule out a bad head gasket, so i did a compression test and came up with
compression test results:
190-190-180-200

engine specs:
D16Y7 block
D16Y8 head
rebuilt to OEM specs about 5k miles ago

Any other ideas besides the radiator cap?
Am I correct in thinking those comp. test #'s are OK?

and YES, i did search, and NO, i'm not a noob. thanks

 

The radiator cap would have been first on my list.... but if that doesn't cure your problem, make sure the thermostat is opening....

And yes those are good compression numbers.

 

yep, so far so good with the other rad cap. the older one (that is on there now) is a nippon denso, but the newer OEM one is a different brand and shaped a little differently. has a TR marking on top?? seems to be constructed the same on the underside, but the ears on it are bent down, maybe causing it to not fit correctly??

forgot to add that the thermostat was replaced with an OEM unit about 5k miles ago also.

 

well, i thought the different rad cap fixed the problem, but i am still having the same problem of the coolant overflow filling up and not going back into the radiator.

another thing i've noticed is that when i do take off my rad cap, there is pressure released, even after cooling down overnight.

could the head gasket still be to blame after the compression test checked out, and i don't see any coolant in my oil? i have noticed a VERY small amount of sediment in the bottom of my coolant overflow which could be oil... maybe.

 

bump for any other ideas before i go ahead and change the head gasket??

 

Water pump?

 

I recently had this problem when I installed a new OEM short block.

- Burped coolant a number of times
- New OEM thermostat & it opened correctly
- New Buddy Club thin headgasket
- Replaced the radiator cap
- Fans came on correctly
- Compression test was fine


At the referral of a friend who is an Acura-tech, I bought one of these radiator funnel kits.


I put it in place and pressurized each cylinder. Sure enough, found that was significantly leaking: ie. headgasket not sealing. The leaking cylinder(s) will cause the radiator fluid to bubble.

Upon pulling the head we found that when I lubed the head bolts with oil I used too much and it had pooled in the bottom of the hole. When the bolt was torqued it compressed the oil preventing the bolt threading deep enough even though the torque reading was correct.

Cleaned everything, replaced the headgasket, and all is good now.

 

is the head flat? how about the block? did you replace the head studs when you put the head back on. the studs can stretch form time to time

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RStoR &raquo;</TD></TR><TR><TD CLASS="quote">...Upon pulling the head we found that when I lubed the head bolts with oil I used too much and it had pooled in the bottom of the hole. When the bolt was torqued it compressed the oil preventing the bolt threading deep enough even though the torque reading was correct.
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hmm, good to know, will check them when i do pull the head. thanks.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by riceburner700 &raquo;</TD></TR><TR><TD CLASS="quote">is the head flat? how about the block? did you replace the head studs when you put the head back on. the studs can stretch form time to time</TD></TR></TABLE>

the head was checked for flat at the machine shop when i dropped it off for new valve seals and hot-tanking.

i checked the block with a straight-edge i have and it was fine.

the head bolts were replaced with new OEM bolts.

i went ahead and bought a new head gasket today and will probably throw it on wednesday.

thanks for the ideas and keep 'em coming...