Where is my coolant disappearing to? - 2003 1.6 Honda Civic

TheKaiserChief

Odd one this (or maybe not hopefully and somebody knows what’s happening).
Since I’ve owned it, it seems to go through coolant

It’s not leaking (no signs of leaks on undertray or on my driveway), but is consuming it somewhere as I top up coolant often.

It’s never overheated. But I did the odd time have an engine mgmt light which indicated a missfire in cylinder 3. Changed plugs but still came back again. 

BUT the car always drove fine, never missfired, just got the random eml on with “missfire cyl 3”.

I’ve been told it’s a closed system, so why can I keep topping up coolant as it is?
I’ve gone through 5litres ready mix of coolant in 10 months.

The reason I first noticed it was low on coolant was it wouldn’t blow warm air, a friend mentioned it could be a coolant issue. It was low, that’s how I found this.

Can anybody help ?

TL;DR:
Car losing coolant, don’t know where, not leaking, never overheated, got odd “missfire cylinder 3” message, but no missfire.

biko

Try swapping the radiator cap.

JohnBoy26

is it the radiator or the bottle you are topping it up from?

It could be a blown head gasket. It rarely happens these but it's not unheard of. Your best bet would be to get it diagnosed properly by a decent mechanic.

TheKaiserChief

@ biko the rad cap seems solid and sealed. THeres never any residue on the outside of it.

@ Johboy26 Im topping up by the radiator, until it fills. If the headgasket is gone, why isnt it overheating? I was always told itll overheat. It never has

jimgoose

Any sign of coolant in the oil? If not, it sounds like it's evaporating through a leak somewhere.

TheKaiserChief

@ Jimgoose Do you mean like "mayonnaise" under the oil cap?
If so, no there's not. Dipstick looks ok with just oil, and when I look down after taking oil cap off, the oil looks normal too.

H3llR4iser

The heater not blowing warm air means there's very little coolant remaining in the system. I suspect you might very easily have a blown head gasket, unfortunately.

First step would be to have a mechanic run a pressure test on the cooling system (or you can do it yourself if you can access the appropriate tools), if there are any relevant leaks outside of the engine (radiator, pipes, bottle) it might become visible with coolant bubbling around the area.

TheKaiserChief

@ H3ll4iser When I top it up with coolant it blows warm air again. it just stops blowing warm air if the coolant is running out or if I need to put some more in.

Can a headgasket go but the car not overheat?

Markcheese

I'm having a similar issue with my fabia, been topping up since April(when a new thermostat installed) but it's running sweet ... Mechanic was reckoning it was the head ... Thought it would have gone by now ...

biko

Possibly but also there could be tiny cracks in the system that will let water evaporate under pressure. I has such a crack on my expansion bottle once.

Gavman84

I had my coolant disappearing on my focus recently turns out it was the frost plugs not sure your car has or not??

H3llR4iser

TheKaiserChief wrote: »

@ H3ll4iser When I top it up with coolant it blows warm air again. it just stops blowing warm air if the coolant is running out or if I need to put some more in.

Can a headgasket go but the car not overheat?

Technically speaking, there is such a possibility if the leak is small enough - I had a leak near the pump on my car, it would drop almost all coolant in the space of 50 km, and yet there would be no overheating; Yet years ago, on a different car the cap on the overflow bottle developed a small crack and the water was boiling within 3 minutes...

What's certain is that the coolant has to go somewhere; Does the exhaust have a white/bluish smoke under heavy acceleration and/or does it release a very "sweetish" smell?

Chris_Heilong

I would say head gasket

biko

Head gasket is to Motors forum what Lupus was to House

Is there any smoke/smell at all from exhaust on startup? It may take a minute for it to start smoking so leave it running a while/rev a couple times.

irish bloke

I wouldn't be so quick to diagnose head gasket.

Can you feel anything with the expansion cap off, blow etc.
Has already bring suggested but get a pressure test completed.

Had a car that was loosing around the same amount of fluid as you, never a puddle or evidence of leak. Turned out it was a leak in a pipe where the coolant was landing on the exhaust manifold thus evaporating away. Fault like this could leave a chemical odour in the cabin.