cbr_ryder

OK, here goes…. I have had an overheating problem with my 1986 Honda Civic 1.5L

12V carb. This has been an ongoing problem for, I’d say close to a year and a half.

So the problem is I am not getting any coolant flow through my radiator. The bottom

rad hose and radiator stay ice cold even though my engine temp is reaching max. My

temp gauge and temp sensor are reading fine, I have used a heat gun to check this.

The only way I am able to drive my car is by cranking the heat and staying off the

highway. I have a bleeder valve for the coolant, I bubble the system the coolant

starts to flow fine, fan kicks on, everything is good…Until I take it for a drive, it gets

air locked again, and I no longer have coolant flow and my engine starts to overheat.

So yes this does sound like a blown head gasket, but I start from the ground up

trying to solve this problem. First thing I did was replace the thermostat thinking it

might be stuck closed. That didn’t work, I put in a new radiator and rad cap, still

nothing. I check the water pump, it’s fine. I have no leaks, all hoses are good. So I

rip the head off, check the head gasket, looks fine, no sign of breakage. I get the

head cleaned up and the base milled, the head had minimal warpage. I buy a good

quality head gasket set, replaced all the seals, cleaned up the block really well put it

all back together all nice and pretty…you guessed it same deal.

I’m pretty frustrated by now, I figure it must be a cracked head, I go to the

wreckers, pull off a head clean it up, put it on, problem still remains. I consult a

mechanic, he tells me that it has to be a cracked head and that I must of just had

some bad luck and grabbed another cracked head. I wait until another one of my

cars shows up at the wreckers, and rip off yet another head. Clean it up put it on,

nothing has changed! Same symptoms exactly! I think I’m safe to say it isn’t the

head, so now I have 3 perfectly good heads and an engine that keeps overheating!

I know all of you are saying, just get rid of it, but I can’t let this car beat me. So the

only other thing I can think of now is, it must be a cracked block. So if any of you

have had experience with this car, and could lend any ideas as to what the problem

could possibly be besides a cracked block or any of the other things I have

mentioned above, I would greatly, greatly appreciate it. If I can’t find a solution I’m

grabbing the block that I took the last head off of and doing an engine swap. You can

understand my frustration, I am a 4th year mechanical engineering student, with the

little spare time that I do get I have done all this work outside in the winter, I just

want this problem to be solved! Anyways thanks for reading, hope someone can

help…

kine462

why don't you just pull the motor and put in 88 teggy (integra) motor and sell all that crappy 1.5 carbed motor!!!! You have more money into the changing the head than just to change the motor. Or you take one of the heads to the machine shop and ask them to check it for you. And I hope you are using new headgaskets/head bolts otherwise you will have the same problem ever time.

RHD_BB4T

I have seen a few guages go bad.. Buy yourself a infrared temp gun and see if it is actually overheating. If it is the only other thing I have seen is a bad water pump... you said you checked it... have you actually taken it off and looked at the fins on the back of it ?

cbr_ryder

I did check the engine temp with a temp gun, definitely overheating. I took the water
pump out, checked it, rotates smooth, no play, fins perfect, and changed the o-ring
seal....I've thought about putting in the ZC but I don't feel like spending the money on this car. Plus this crappy 1.5L carbed motor gets 5.7L/100 kms, which is all I can
really expect to benefit from with this car. I have a buddy that works at the junk yard on the weekends, he charged me $35 for the heads. He'll give me the block and tranny for $50-$75. Yes, I use a new head gasket every time, that's the only other real expense at $18 a pop. I had the last head checked by a machine shop they said it was perfect...Yesterday my thermostat had finally had enough and is stuck open, now i have to keep a piece of cardboard infont of the rad b/c it won't heat up. As soon as I put in a new thermostat it will overheat again. I'm going to grab that block tomorrow, kinda running out of options here...

EMod Civic

I've delt with these cars for many years, and I've never seen a cracked block or head. Are you sure the thermostat is in the housing in the correct direction? If you are overheating and the radiator is not getting hot, then either the thermostat is not allowing coolant to flow, or something else is not allowing coolant to flow. When operating correctly, the lower hose should be hot, and the upper should be cooler. If the upper is hot and the lower is not, then there is no flow through the radiator. Have you checked the rad hoses for blockage? What about the radiator itself? Have you tried flushing the system with a garden hose? Did you try to twist the water pump on it's shaft? The impeller could be loose from the drive wheel.

-Chris

cbr_ryder

My roommates dad, who has been a mechanic for over 19 years and owns his own

shop, ice races these cars and has seen numerous cracked heads on them. He

also said he has never seen a cracked block on them. I should probably tell you,

that my brother had crashed the car a few years ago and drove home with it after

all the coolant had drained out of it. That doesn't make sense that the lower hose

should be hot, and the upper should be cooler. The coolant comes from the engine

goes through the upper rad hose into the rad and back up through the lower rad

hose to the thermostat. The upper rad hose in return would be the hotter of the

two. The radiator is brand new too.

EMod Civic

You're right about the collant flow direction - I don't know what I was thinking. The point is still that if the two hoses aren't both hot, then you aren't getting any coolant flow. How are you bleeding the cooling system? I always run with the rad cap off, open the bleeder port and keep it topped off, letting it drain from the bleeder hole. After a while of solid flow from the bleeder, I close it and continue to run for several minutes. The engine must warm up enough to open the thermostat to bleed the system. It should be obvious when the thermostat opens. For really stubborn air bubbles, I have also disconnected one of the small coolant lines that runs to the throttle body and connected a length of tubing and pulled a high vacuum on it. You can also bleed from this location by using a length of tubing (to add some pressure so it doesn't just spray out).

Have you tried removing the thermostat completely? Are you sure it works? Are you sure the housing isn't warped or something causing the thermostat to not open? Are you sure the thermostat is installed in the correct direction?

Any cracked motor component that is allowing combustion to be exposed to coolant is easy to check for. A decent mechanic shop will have an analyzer that can detect exhaust gas content in coolant and can very quickly and cheaply determine if the issue has anything to do with that. At this point, I think it would be well worth the money to have that checked.

-Chris

cbr_ryder

Yep I bleed the system just like you say, I even sometimes drive it up ramps on a bit of a hill so that the bubbles will migrate to the highest point in the system, the rad filler spout. Yes, I've removed the thermostat completely and the problem almost seems to go away, takes a lot longer for it to heat up and temp doesn't get too high on the highway. I believe it is the thermostat housing where the bubbles are getting stcuk, removing the thermostat alowed the bubbles to flow. I have honestly gone though 6 to 8 thermostats, they work for a while but after repeated overheating they give out and are easily opened with minimal heat and pressure, allowing the coolant to flow similar to if I remove the thermostat completely. 100% positive it is installed in the right direction. The housing is fine, nothing would stop the thermostat from opening. A combustion leak test kit from Napa will run me about $50, and I'm sure a shop will charge close to that too, I am fairly confident that it is the block, and I'm gonna swap it out at the end of April. Thank you very much for all the help, I'll be sure to keep you posted once I have the new block in.

cbr_ryder

Update:

My car has started to use up quiet a bit of coolant, like 500 ml of coolant per 150km, and the bottom of my rad cap has oily, carbon like black stuff on it.

cbr_ryder

Ended up being a faulty temp gauge...