Since I bought my latest CB (1990 Accord EX) a few months ago, I've been having cooling issues. For days at a time, the temp gauge would only reach normal operating temp at idle, and once moving along the highway, the gauge would drop down to C. After a few days, it would start to rise towards H. I would stop, put some coolant in and it would start over. So I last week, I had the radiator, thermostat, coolant temp sensor, and reservoir all change. This all made the car operate at even lower temps. Last night after parking, I heard a slight tick or steam pop sound coming from the driver side fender, paid it no mind. Today while driving, I noticed steam coming from under the hood on the driver side first, then passenger side. Within a minute, the temp starting rising. Did the usual, pulled over and topped of the coolant, however the reservoir was still full. I had to do this a total of 5 times (one involving a stop at a gas station in which I emptied an entire bottle of coolant into the radiator) before eventually making it home. After parking, I noticed literally every drop of the entire jug of coolant leaking out from the back driver side of the motor. Also, each time of pouring in more coolant, it would start to spit back out at me. Please help.

 

Well, you got a lot of stuff going on. You need to rent a coolant system pressurizer and put it to work by pressurizing the system. Then fix the leaks. After fixing the leaks you need to idle the car and check that the lower radiator hose is getting hot as the car warms up, as it gets closer to regular operating temperature on the gauge, the lower hose will finally start getting hot. If not, and the car starts to overheat before the lower hose gets hot then you have the wrong thermostat in there. You should only be using Honda OEM thermostats and cooling system sensors and switches. Aftermarket are prone to failing after one or two years and if the gauge reaches red before you catch it you could warp your head. If the lower hose gets hot as the car has warmed up then next you need to watch that both fans come on as the car continues to idle. Both fans should run before the gauge starts to overheat. If they both fail to run then either a fan is bad or you don't have the correct fan switch installed(or it's in the wrong spot, it needs to be installed where the lower radiator hose goes in the back).

 

A question please. I have heard that Honda thermostats were designed to "fail" in the open position. Is that true or not?

 

90CB7EX, verify that your system was properly bled via the thermostat bleed screw.

Fitz, from my limited experience the two failure modes I have seen are the strap busts and leaves the valve open, the other is the internal part of the thermostat piston fails and it is also left in the open position. Only use Honda thermostats, they cost a bit but seem to be reliable and fail in a favorable position(open).

 

So I went out to the car today, started it up and let it idle for about 10 minutes. It reached normal operating temp but did not start to overheat. The lower radiator hose did warm up, but did not get very hot. I have videos attached below. One video is from last night when I got the car home. It shows the steam and where the coolant was leaking from (sorta). The other video is from just now, after I shut the car off. I was able to capture the hissing noise it started making from behind the motor after shut off. Hopefully this slims things down a little.

http://vid1105.photobucket.com/album...psm7l3ill8.mp4

http://vid1105.photobucket.com/album...psq62mbfls.mp4

 

Given the location of the leak, it seems likely the water pipe to valve hose is cracked and leaking.