Mystery coolant leak

Looks like my Civic got jealous of the Volvo's coolant leak and decided to follow suit.

It's an 89 Wagon with a B18A1. It seems to leak when it wants. Sometimes you drive it and get a giant puddle, when you try to figure out exactly where it's coming from you can let it run forever and nothing. I have been able to figure out that it is not the water pump or overflow reservoir.

When i finished my paper route this morning at 5am i popped the hood and was able to see it was coming from somewhere in the vicinity of the t-stat/upper radiator hose/lower radiator hose/heater core hose area. Unfortunately is was dark and that's the best i could do.

Since i've noticed this problem I noticed the car has been running a tad cooler than normal when it's got plenty of coolant in it. Probably 1/3 on the gauge instead of the normal half. However, sometimes it will go up to 2/3+. When this happens, it seemingly randomly cools back down to 1/3 after a while. It cools down over the span of 2-20 seconds. At this point i add coolant and all is well for a while.

Is it possible that the t-stat is getting stuck shut and the pressure is forcing coolant out? Then it opens and gets stuck there making the car run a little cool?

I know this is confusing but i'm confused so yeah......

any ideas are appreciated,

Jacques

PubBurgers wrote: Is it possible that the t-stat is getting stuck shut and the pressure is forcing coolant out? Then it opens and gets stuck there making the car run a little cool? I know this is confusing but i'm confused so yeah......

Hum, I hate these problems and I'm not good at fixing them. But I'll give it a whack.

T-stat getting stuck then unstuck? Guess it could happen, but that would be a new one on me. My guess is you have some crap in the system. Probably some blockage in the radiator and it's floating around in there. Sometimes coolant can get through, other times it can't. But t-stats are cheap and no reason not to throw one at it.

The unusually low reading on the gauge might be because things are't flowing well. By the time the coolant gets to the gauge sender it's cooler than normal because it's been sitting in a t-stat housing or something for longer than normal. In other words, localized cooling, but not cooler over all. That might be what you were saying.

Dunno, just throwing out ideas hoping to help you think it through. I could be dead wrong. I don't know Civics from a hole in the ground.

Good luck,

Ed

Rent a pressure tester. Running cooler most like means an open thermostat.

Autozone has a pressure tester you can borrow in their Loan-A-Tool program. Borrow it and use it.

Had a problem similar to that once. Turned out to be a pin hole in the radiator. I see a pressure tester and a UV light in your future soon.

The weird temp readings will be because of the fluctuating coolant level, most likely. There is a maze of hoses and fittings around the trans end of the cylinder head, and under the intake manifold of most every Honda. Get a good light and a small mirror, make sure its full of coolant, then either pressurize it with a tester, or drive it till its hot. You will probably see a small stream from a split hose somewhere.

'fingertips to forehead...I foresee some quality time with a pressure tester in your future...

Seriously, if you haven't seen bubbles in the radiator, or smelled evidence of combustion there, you really have few options...Sorry. That's the way it is when you buy one-a them there furrin cars.

Not that I've EVER had it happen to me, you understand...

The thermostat won't create the sort of back pressure that will blow out a gasket. But since you've seen a leak there, pursue it and find it and fix it. Likely just a shot gasket, especially if the previous owner replaced the thermostat but reused the old gasket to save a buck. If you've got gasket goo, use it.

And as long as you're there, you might want to consider replacing the thermostat. The temperature fluctuations are likely due to the erratic water levels (temp sensors don't read hot air well), but a sticking thermostat can cause the same fluctuating readings.

When I had a Honda I always had issues with aftermarket thermostats. For some reason the Honda thermostats work and others - not so much. This may be adding to your issue.

Think I may have found it. One of the tiny half hidden hoses going into the heater core had a tiny hole. We'll see over the next couple days....

thanks!

Jacques