Rep Power: 0

Hey All,

I have a 1996 Honda Civic DX Coupe,

So I recently replaced my radiator, it was the original one from 1996 as it was stamped inspected on 1/25/96, it developed a very fine hairline crack on the front side pretty much opposite from the upper radiator hose about 5-6" long, I also took the liberty to change the Thermostat while I was at it, not sure if I may have made a mistake along the way though, I got one that supposedly opens at 170F, not sure what the stock one opened at, or if this is the explanation for this problem, I did indeed test it in a pot of water prior to installing it and it was opening and closing as it should.

Anyways, I did the whole process of bleeding the system afterwards for about 40 mins while the front end was up on ramps, kept burping the upper radiator hose and lower one once the Thermostat opened, also the bypass hose and heater core hoses, needless to say there was some air in the system of course, I'm pretty confident there is little to none left now as I did a second bleed session at operating temp and barely anything came out while burping, if I just let it idle, nothing came out at all.

Anyways, here is thee weird part, when I'm bleeding the system, the thermostat seems to open up around 84-86c, cause the lower radiator hose starts to get warm/hot, so I know coolant is flowing through it, but when I'm actually driving the car to and from work, I see that the coolant temp is in the mid 80's on my OBDII scanner, but when I get out of the car when I either get to work or home and feel that lower radiator hose, it feels cold as if the thermostat isn't opening, keep in mind it's about 20-30F in NEPA at this time so I'm not sure if this sounds like normal operation when the cabin heat is on? I'm pretty confused right now.

Is there any scenario in which the water pump would be the issue? Car isn't overheating at all, and actually the power is pretty good so I wouldn't suspect overheating. The Temperature needle stays just below the upper indicator water lines.

Any help is appreciated 😊

 
Rep Power: 222

Because its cold out, the heater core could be all the car needs to prevent overheating. The rad is only a bit more than twice the size of the heater core. As long as the upper hose isn't screaming hot, you don't hear the coolant boiling, and temp gauge is reading ok i wouldn't worry about it.

 
Rep Power: 0

so another revelation this morning, started the car, left the heater fan off, drove about 6 minutes to get gas, temp gauge was already up around mid to high 80’s, when I stopped at the pump the engine seemed bogged down, turned the heater fan on and the car came back to about 720 rpm’s within like 10 seconds, also naturally the temp started to go down quite a bit, then going down the mountain I coasted in D4, and the temp almost dropped below 70 with the heater on, and I saw the temp gauge drop. All the while I was bleeding the system and the temp gauge said around 88c the lower rad hose got hot, but when I drive to work and it reaches the same temperature, it never seems to be hot. I’m puzzled, brought it to the garage next to my work, they’re gonna do a compression test and check the water pump.

 
Rep Power: 222

You might still have an air bubble. Did you have the heat on max while you were bleeding? I like using a bucket funnel to increase the head pressure

 
Rep Power: 0

I had the heat on max with the fan off as is the recommendation, also was using a spill free funnel, and yesterday I decided during the second bleeding session to add the extension to the funnel to further raise it. Bubbles were coming out, but it seemed like only when I was burping the hoses, at a certain point not much or anything was coming out at all.

 
Rep Power: 222

Hopefully you got the rest of the air out now

 
Rep Power: 0

Not sure about that.... Replaced the thermostat, I can confirm when I was bleeding the system yesterday it was opening cause that lower radiator hose was almost just as hot as the upper, but cars still acting fishy, had the overflow filled to the minimum line last night, drove to work this morning and it seemed like it was still at the minimum line when I checked after I pulled in, went out quickly around 10:30 this morning and checked, was about a whole 2 inches below the min line, filled it up before leaving work tonight again to the minimum fill line, come home and it's more than halfway to the max line which is a good 2 inches....

At this point not sure where to go, I want to keep living in denial that it's not the headgasket, but something tells me the moment I pull those spark plugs out and put the camera down the cylinders, I'm gonna see coolant at this point... Lol, it's the only thing that makes sense at this point, the extra pressure is pushing it into the overflow after I drive, and the system is siphoning more coolant than it needs while the car is cooling down cause it "lost some" or it's pushing it into the cylinder/s.

tell me what your theory is on all this, I don't think this car has ever overheated, never had any signs of it, now I'm torn between just pulling the head off and checking if it's flat and if it is just slapping a new headgasket in and just riding it out and seeing how long it lasts, or just parking it/selling it to someone else that would want to do the job.

 
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Here's a question maybe you can answer, so I installed the new radiator and used the cap that came with it, it says 0.9 which I assume means 0.9Bar which is 13PSI, and the old one from the OEM radiator says 1.1 which is 16PSI, I noticed if I squeeze the upper radiator hose good enough with the car off I can get coolant to go into the overflow, with the old one is seems impossible,

I'm assuming I should NOT be able to do that? Bad radiator cap perhaps?

 
Rep Power: 0

Well, left for work today, temp gauge took hella long to even get above the C mark, then going up hill up the mountain it got to just below the top waves on the gauge which is where I’m used to seeing it, but then coasting down it went all the way down pretty much. Got on the highway and it climbed back up pretty quickly. 🤷🏻‍♂️ overflow was low again this morning after I did a top up yesterday after trying to bleed again, maybe it’s the water pump? But not exactly sure how to test that tbh.

 
Rep Power: 222

If it's losing coolant it's going somewhere. If you can't find the leak its going out the tailpipe unfortunately