my gf has a 1993 civic ex sedan with a b18c1 swapped into it.
ever since she has had it the temp gauge has gone up and down. it was comporession and leak down tested and came out great, with compression in the 210-220 range on all 4 cylinders. there has been no mixing of coolant and oil either. jsut the crazy temp gauge. this summer it started over heating. we swapped in a brand new 1 inch thick aluminum radiator recently and i noticed it would NOT bleed. it appeared exhaust was coming through the coolant. so i had the head cleaned, pressure tested and surfaced and put a new head gasket it. changed oil etc, refilled coolant, let ir idle for like 15 minutes, took it for a drive. the temp STILL wanders though it tends to stay in teh middle a LOT more. before it would heat up as you revved, as if the pressure was increasing in the cylinder and allowing the exhaust to leak...now though the temps tends to drop as i rev in general.
I dont know waht to do next.
new radiator, working fan (wired always on now), water pump changed 18 months ago when swap was done, new head gasket, pressure tested and surfaced head....anyone have ideas?

 

Is the heater core valve open or closed while this is happening?

Try testing it with the heater core valve CLOSED, and see if the problem is fixed.

Also completely flush the system. I am confused on how you said it would not bleed. Make sure you are also running 50/50 distilled coolant or distilled water with coolant.

Plus, you are not leaking, steaming, or burning coolant correct?

Keep us posted.

 

thanks for the fast reply, you were one of the ones i was hoping would see this
no steam at all though right now, no burning coolant smell, exhasut smells like typical catless honda exhaust.
as far as it not bleeding, that was before the head gasket, basically i would bleed, and then 5 minutes later i could bleed again since air/exhaust was getting into the system somehow. bubbles in the coolant (very slight), bubbles of air coming out the bleeder and then bubbles in the overflow, but NOT boiling.

i will double check the heat core on it i am PRETTY sure it was closed but the car DOES have 207k miles on it and i would not be surprised if it was a part of the problem.

 

thanks man.

The mileage shouldn't really be a problem. That is a lot of miles, but with the replaced water pump and headgasket, the motor should still be good.

However, it could have corrosion build up with inside the motor, or the main water line (from the thermostat to the water pump) with corrosion or some flowing problem.

Have you replaced the coolant sending unit, or the ECT (engine coolant temp switch)?

They are both spring loaded, and could either be sending you a false signal to the gauge cluster.

Have you also tried jumping the fan to run all the time to see if it over heats? If that is the case, and it runs just fine, then that's the ECT problem.

If you are 'overheating', try getting a thermostat (one to measure the temp of liquids, etc. -- not the engine thermostat), and see how hot it is. It should be no more than 215° inside the radiator.

If the heater core valve is open while it's over heating, it could potentially be a flowing problem with the heater core.

I'd recommend flushing the whole system, run w/o a thermostat, jump the cooling fan, and also get some coolant flush cleaning bottle to burn all of the corrosion within the motor as well.

 

yeah wehn we got the swap done we had new oil pump, new water pump and so on done to it. they supposedlyt swapped the ect and coolant sending unit with known good ones at the time, but they ahve not been touched since then. currently the fan is on with the ignition all the time and it seems to help a little but not a lot...
inside the block there was not excessive corrosion that i could see...but i will go ahead and plan on a real engine coolant flush with some sort of cleaning agent ot see what it does.
before then though i will most likely pull teh thermostat (not like i need it AS much in texas during the summer), and manually push the heater core valve closed to make sure it is sealing.

as far as adding another sensor to check teh actual temps would an autometer be reliable enough? that way i can get one to test and then give it to her brother for his car...he lieks that stuff a lot more than she does.

thanks for the suggestions, having another person to point stuff out helps a lot.

 

Yeah, just any standard thermostat that can go up to that high of temp would be good. Just basically making sure the temp switch has an accurate reading.

Has this been happening ever since you swapped in the motor, or just started happening type deal?

Reason I say this, is because, while getting emissions done with my car, I accidently broke the coolant sending unit while adjusting the timing on the distributor (since it's right underneath), and went to AutoZone (dumbass me), and got a new one that was not OEM honda.

I swapped it in, and the sending unit was condiserably bigger. I installed it, and had cooling problems left and right because the damn aftermarket unit was blocking flow in the head. I went to Honda and got an OEM sending unit, problem solved.

How high does the temp go? Higher than half?

When the engine is over heating (not to the point of the Red line of course), but feel the hoses. Are they both hard and feel like there is a lot of pressure in them?

Also feel (of course don't burn yourself), but feel the top part of the radiator (near the upper radiator hose), and feel the bottom part (near the lower radiator hose) to see if they feel the same temperature.

This way you can see if there is a coolant flow problem.

With my problem of the sending unit, it was very strange, the top radiator hose was hot as hell, and pressure build up (hose being hard), and the lower hose was soft and room temperature type deal...also at the lower part of the radiator was cold. So it was definitely a flow problem.

 

it had been happening ever since the swap was done but the guys at the shop even kept it an extra day and could not find anything wrong that they knew of. it never was that bad until a few months back.
currently it sits below half then will blip up to like 3/4, then drop just below half...i really should take a video of it sometime...its interesting to see it happen. before the head gasket and radiator installs it was boiling over.
i have not yet had a chance to fell teh pressure in teh hoses since i jsut got it tunning again tonight and have put less than 10 miles on it so far. Tomorrow i will aim to check pressure by feel in teh hoses, and also feel the top and bottom of the radiator as well.

is it safe to assume that pretty much all obd1 honda ect and other temp sensors are puretty much all teh same? i have several known good ones on F series engines...

thanks again, this has been driving me nuts for a while now and i have nver had a problem with any other setup i am using the same radiator that i use in my h22 hatch in her car and its jstu annoying as hell!!

 

lol. I know you'll get it. it's a bitch, been there done that

 

well today the temp satyed right on target.
after the drive home where it was acting up after the new headgasket i had only driven a mile or so round trip to work.
today i let the car run a while but also noticed that the overflow tank was empty. so i drove to a gast station left it idling and topped off the radiator and so on. let it run for a while and went for a drive....and temp stayed right where it should around 1/4. i got to work and sat a while longer with the a/c on and the stereo up to make sure it would stay stable and it did....

so MAYBE i jsut didnt bleed the coolant system well enough and there were trapped bublles that came out while driving home the other night. I am still going to check things as you suggested, Poison...but for now things look good and i am relieved cause i havent driven my accord in 3 weeks.....my gf's car is fun, but my other car is NOT for daily driving...