1994 Civic LX. Everything is stock. 1.5L 16valve

My troubles started in March when I had to have the radiator replaced. In early April, I had the temperature sensor and thermostat replaced (this was when I wasn't doing these things myself, it gets better later on.) I spent the entire summer adding coolant here and there. I *knew* I had a leak but I couldn't find it and a pressure test told me that I needed to replace my head gasket. I figured out that my radiator fan wasn't turning on. Used a voltmeter, everything checked out on the fan itself, the wiring leading to the fan, checked the temp sensor plug, put heat via hot water to the temp sensor and it checked out. Got fed up with dealing with it because all my wiring still has the original armor/heat flex on the wiring. Direct wired a switch underneath my driver's dash to turn the radiator fan on. A few weeks ago, I (like an idiot) decide I'm going to do my best to be cheap and drive this car until the wheels fall off; I purchase the Blue Devil gasket sealer. I ended up finding my leak, coolant was steadily pouring from one of the water pump mounts. Thought it was strange it took about three gallons of coolant. I took the car to a family mechanic friend who replaced the gasket, water pump, and timing chain for me. Head was taken to a machine shop, it was cleaned, surfaced, and pressure tested.

Now here's where my issue comes in. My temperature gauge says that I am still overheating, as in pegged ALL the way out, past the red. I cannot, for the life of me, figure out what my issue is. I flushed my radiator (there's a bit of sediment and other crap I can see at the top when I take the cap off after the flush) replaced the coolant temp sender (the one under the distributor), replaced the thermostat (there was a bit of built up white stuff on the spring part and yes, it's installed correctly), and am getting ready to replace my o2 sensor (the CEL had come on, used the paperclip test, light pinged a 41, unrelated to this issue I think.) Using an IR thermometer and thermometer clamps, when it's supposedly overheating, according to the gauge, my top hose coming from engine to radiator is reading around 195 deg F and the bottom one is reading around 140-150 deg F, so I know that water is being moved and the thermostat is opening up like it should at a certain temperature. I've also bled the coolant system via the bleeding nut? Added coolant until it ran, closed it off, starter car and let it idle and then closed the nut when it didn't bubble. The strange part is I can't seem to get any hot air to blow at first and even then, it's not like the bowels of hell like it used to be. At this point I'm thinking a few different things but I can't be for sure:

1) I have a clogged something somewhere, whether it be a hose or maybe my heater core? I know there's crap in my radiator but it was flushing out okay from the drainage hole. Water flow was fine.
2) I have a short in a wire somewhere that's either pertaining to my temp sensor or the coolant temp sender? I have no clue.
3) Even though the temperature gauge works, it could still be broken?

At this point, I've dumped all of my summer savings into this and frankly, I'm tired of fooling with it. I'm tired of stressing out about if my car is going to make it somewhere or if it's going to overheat. I just want the dang thing to work. All that said, thanks for reading my novel. Hopefully you fine folks can help me figure something out.

 

That white stuff you're finding everywhere is Blue Devil. It will clog your radiator and heater core. I don't think there's any good way to remove it other than replacing the parts. You could try disconnecting the heater hoses from the engine and flush the core forward and backward by holding a garden hose onto the heater hose.

There are two temperature sensors under the distributor. The one with one wire controls the gauge. With the wire unplugged the gauge should stay all the way below Cold. If it is staying at 195 (normal) and not boiling over the gauge could be wrong.

 

I replaced the sensor with the smaller connection under the distributor. Which hose should I be looking for to flush? I'll admit I'm a bit confused when I look at most of the things under my hood.

 

*Update*

Found my heater hoses based on diagrams. I flushed them both ways for a few minutes, used CLR, and flushed them again. Liquid that came out wasn't dirty at all and didn't have and sediment. Ran the car at 2500 RPM for approximately three minutes before the temperature gauge started going up. Stopped in the red this time. I don't have the IR thermometer or clamps with me to test hose temperatures but the outgoing hose on my radiator was cooler than my ingoing hose. Could touch and hold both with mild discomfort. Heat blew hot for a while until the temp gauge got to the red and then it cooled down. Didn't check radiator because I didn't want coolant to spray everywhere/risk losing a hand, but the reservoir tank was still at the same level I left it.

Extremely confused at this point and have no clue what it could be.

 

Any luck on your issue? I am in a similar situation (and yes, it has everything to do with blue devil).

 

Jack the front of the car as high as you can and then take the rad cap off and start the engine to bleed the air out of the system. The way you describe it, it sounds like you have a heck of an air bubble in the system. Either that or there is a leak in the head gasket.. Does the car leak antifreeze? Are you gaining oil? Does the oil look like a chocolate shake? How long will the car run before it over heats and dies? If it never dies then chances are good your not overheating. but are getting flakey gauge readings. coming out of the thermostat housing the hose should be hot, around 190 but not above 210 degrees after about 20minutes.

 

recently replaced ect sensor and holy hell bleeding was a nightmare.
fully warm, jack up, heater on, cap off, squeeze the hell out of both hoses
and watch for bubbles escaping. finally back to normal.
stripped the block drain plug so couldnt get it out, likely would have made it easier.

 

How did you strip the block drain plug?

 

Some block plugs won't come out at all. Pretty much fuses to the block after years of heat cycles.

 

I was going to suggest this same thing.

One of my hoses to the heater core was leaking and once enough air got into the system, the car overheated and my heat was sporadic for a couple of days, as well as I had pretty bad idle surge first thing in the morning.

You air pocket is is setting behind your temp gauge sensor under the distributor.

Make sure to put your heat on high (no fan required just cabin temp slider all the way to max hot), fill up your radiator and make sure the nose of the car is pointed up and not down, even a mild grade works.

It can take a bit for all the bubbles to stop flowing from the bleeder screw. Do this with the car running and the radiator cap off or just barely sitting on.

I actually just went through the process tonight and it took over 40 minutes for the fan to kick on and I actually had to put the hood down to trap the exhaust header heat to fully warm up the motor.

If you don't have the factory service manual to purge the air properly, let me know and I will post up the page for your car.

 

The other way to purge the air is get yourself a spill free funnel.

https://www.amazon.com/Lisle-24680-S.../dp/B00A6AS6LY.

Clamp on the funnel, fill up the rad, run it on max heat (no fan) until the fan kicks on, fill back up, air pockets gone. Spent about 20 minutes today bleeding it out myself after changing out the fan switch, gauge and ect sensors on my 98 EJ6. Seriously saves me a lot of time when burping someone's cooling system.

Chances are you may also have to replace at least the gauge sensor (get another one from a pull a part) if not all 3 due to the Blue Devil.

 

That funnel is sweet!

 

Had this thought too.

Was wondering if the blue devil is bad enough that it could clog the passage completely where any of the sensors sit?

Or will it just coat the sensors causing them to get false readings/data from the coolant?

 

That blue spooge you poured in probably clogged up the radiator and heater core. Don't ever use that **** and if you do by pass the heater core and use liquid glass instead and all the intsructions that come with it.

 

Actually lets stop here and add the following: OR ANY STOP LEAK PRODUCT EVER!


Never seen it clog the sensor passages completely but have seen them get a nice crap colored coating resulting in required replacement.

 

omfg...W95 all over again...

 

I wouldn't go that far. W95 would have snapped the sensors putting them back in. OP on the other hand seems to know how to properly wrench a bolt.

Just learning the hard way that there is not a mechanic in a can to fix head gaskets.