Hello everyone! First time posting here 👋

I have a problem with a 2002 Fabia 1.4 MPI, engine code AZF.

We bought it in September 2025 from a family that barely drove it, and before them it belonged to an elderly man who didn’t drive it hard, but also wasn’t very interested in maintaining it properly either.

The little fella has 185k km, and at first glance it didn’t seem to have any major problems when we got it.

One of the first things I did was drain the entire cooling system (it was really dirty, as the eldery man used some type for sealant, probably to attempt to fix the problem that im gonna describe now), replace the old thermostat housing, expansion tank and cap, belts, oil and filters, flush the brake fluid (it was completely black), and clean the cooling system using a Liqui Moly product. After that, I flushed it a couple of times with distilled water before filling it with the correct G12+ VAG coolant.

The car drives great. I also changed the rear shock absorbers, and it does its job well for a little city car.

The problem started a couple of months later, when suddenly the low coolant warning light came on. I checked the entire cooling system for leaks and noticed some residue around the water pump, so I thought: well, they are cheap enough to replace. It was still the original one, so fair enough.

I removed it by supporting the engine from underneath, used some Loctite 5923 to seal it (if you don’t know that product, do yourself a favor and get a bottle — it can seal even the worst engines), and put everything back together.

Since I was already there, I also checked the engine compression. I can’t remember the exact units, but all four cylinders were around 14 bar.

By the way, during all this time I haven’t seen any smoke coming from the exhaust — no blue, white or black smoke at all. Basically, it doesn’t smoke.

A couple of weeks later, the low coolant light came back on. I opened the hood and, indeed, the coolant level was low again.

This is driving me nuts. I can’t find a single drop of coolant anywhere, even after a good hard driving session on back roads. I checked from above, lifted the car and inspected underneath, and all the joints and connections are dry and clean.

Today I also checked the heater matrix, since I read that it can leak inside the cabin, but again: bone dry and spotless.

I bought a coolant pressure tester and next week I’m going to lift the car, pressurize the whole system and inspect everything again. I’ll also take some photos and post them here so you can see the general condition of the engine.

In the meantime, does anyone have any idea what the culprit could be?

By the way, we have to refill the coolant when the light show up all the way to the max (all of this when the engine is cold of course) once every 3 to 4 weeks more or less.

I work repairing industrial electronics and, as you can see, I like fixing all kinds of things, but this thing is driving me crazy because I just can’t find the issue. This engine isn’t even that complicated, come on!

Thank you in advance, and have a great day.

Edited 8 May8 May by Gongal66

Hello, welcome to he forum.

Does the temperature gauge indicate any overheating at all?

Check the EV cap, it is possible that it is not holding pressure when the coolant is hot - resulting in lower coolant boiling point and loss through overflow.

Replacement is not expensive if there's any reason to suspect it.

36 minutes ago, Warrior193 said:

Hello, welcome to he forum.

Does the temperature gauge indicate any overheating at all?

Check the EV cap, it is possible that it is not holding pressure when the coolant is hot - resulting in lower coolant boiling point and loss through overflow.

Replacement is not expensive if there's any reason to suspect it.

Nope, it doesnt overheat at all. I drove it hard to test and it holds at 90°C without a problem.

By EV cap you mean the expansion tank cap? One of the first things that i did was replacing it with a new one from Febi.

If theres an overflow pipe from expansion cap put it into a plastic bottle somewhere in engine bay away from heat and check it after driving a good distance. It will rule out loss of coolant from cap. It may be that the febi one is not quite the same pressure rating as original. Check the engine oil and filler cap for emulsification. Its not unknown for coolant to get into oil but not oil in coolant as coolant may have more pressure than the oil. Last thing I can think of is leaking core plugs. Think there are a few but not sure if there are any hidden behind bell housing. Check base of bell housing for signs of antifreeze crystals. It may be why the previous owner added kseal or similar? I assume you have checked radiator. If its a small leak only once upto pressure/temp it can evaporate before dripping down. The rad and core plugs I know from experience.

Alasdair

12 minutes ago, Alasdair1 said:

If theres an overflow pipe from expansion cap put it into a plastic bottle somewhere in engine bay away from heat and check it after driving a good distance. It will rule out loss of coolant from cap. It may be that the febi one is not quite the same pressure rating as original. Check the engine oil and filler cap for emulsification. Its not unknown for coolant to get into oil but not oil in coolant as coolant may have more pressure than the oil. Last thing I can think of is leaking core plugs. Think there are a few but not sure if there are any hidden behind bell housing. Check base of bell housing for signs of antifreeze crystals. It may be why the previous owner added kseal or similar? I assume you have checked radiator. If its a small leak only once upto pressure/temp it can evaporate before dripping down. The rad and core plugs I know from experience.

Alasdair

Yes there is a small pipe that goes from the expansion bottle to the thermostat housing. How do i need to proceed with the bottle test?

There is emulsification in the oil cap, not much, but i read that in this engine is normal, as we use the car for short city trips, so no time to evaporate all the condensation.

The oil is pretty clean also, once i even drained all the oil into a clean bucket to check it close, and it was totally clean. Could a bad headgasket make some coolant pass to the oil, but not the other way around? Again, the coolant is perfectly pink since the beginning, and not a single bit of smoke coming from the exhaust.

Next week gonna check the core plugs, thank you for the advice.

And i also checked the radiator yes, no signs of leaks either, i removed the fan shroud to have a clear sight and nothing.

The pipe I am meaning normally comes from cap and is open at the end. It usually fed down into engine bay so any loss of coolant drops onto undertray/road. Will check my sons 1.2htp . As to coolant in oil its possible but rare. It normally happens with cracked head/failed gasket when coolant pressure is higher than the oil. Had it on an old toyota that head was cracked and tended to let coolant leak when hot and crack had opened due to expansion. If theres no smoke from exhaust I dont think the coolant is getting into pistons but may be leaking between coolant and oil passage ways in head.

Will as said check my sons

Alasdair

Had a quick look and sorry I was wrong. Theres no expansion/overflow pipe on his so coolant must just drain down sides of expansion. I was thinking of my Seat. You could try some kitchen towel taped around tank to see if it gets wet or even some flour dusted around top. If its leaking it would wash flour away.

Alasdair

Another thought is check the expansion vessel for cracks/damage

Alasdair

1 hour ago, Alasdair1 said:

Had a quick look and sorry I was wrong. Theres no expansion/overflow pipe on his so coolant must just drain down sides of expansion. I was thinking of my Seat. You could try some kitchen towel taped around tank to see if it gets wet or even some flour dusted around top. If its leaking it would wash flour away.

Alasdair

1 hour ago, Alasdair1 said:

Another thought is check the expansion vessel for cracks/damage

Alasdair

I replaced the expansion bottle too, it was a brand new OEM part that i got directly from the dealer. Doesnt seem that is cracked or damaged in any way, and totally clean and without moisture on top.

Also, the trick of pouring flour over the the top was a new one to me, never heard of that trick before HAHAHA

I'd imagine this is a fire-ring headgasket leak. If you take the expansion tank cap off when the coolant is stone cold, and cap hasn't been opened since last reasonable-length drive, is there any release of pressure?

Is it slightly uneven when first cranked over for a cold start?

25 minutes ago, Breezy_Pete said:

I'd imagine this is a fire-ring headgasket leak. If you take the expansion tank cap off when the coolant is stone cold, and cap hasn't been opened since last reasonable-length drive, is there any release of pressure?

Is it slightly uneven when first cranked over for a cold start?

As far as i can remember, opening the cap off when the engine is cold releases some pressure yes. I opened the cap yesterday and didnt release any pressure, but we refilled the tank a couple of days before, dont know if that makes any difference.

And what do you mean with "slightly uneven"?

There should be no pressure when the system is stone cold.

By slightly uneven, I mean like it's easier for it to compress mixture in 3 out 4 cylinders, so a 'lumpiness in the turnover' before the engine starts, and maybe briefly afterwards.

On 09/05/2026 at 18:21, Breezy_Pete said:

There should be no pressure when the system is stone cold.

By slightly uneven, I mean like it's easier for it to compress mixture in 3 out 4 cylinders, so a 'lumpiness in the turnover' before the engine starts, and maybe briefly afterwards.

At the end of this week gonna check it out, if there is pressure in the system when stole cold what could mean? Headgasket?

It starts smooth, no lumpiness or anything. Obviously i do not have the ear of a experienced mechanic but it seems to start just fine.

It might be worth getting cooling system pressure tested when cold. It could be a small leak somewhere that's evaporating when hot and not being spotted. Park up on a dry area when doing it and look for signs of drips.

Alasdair

On 09/05/2026 at 13:04, Gongal66 said:

Yes there is a small pipe that goes from the expansion bottle to the thermostat housing. How do i need to proceed with the bottle test?

On 09/05/2026 at 13:04, Gongal66 said:

Just a quick clarification to help others. I've just replaced the waterpump on my 1.4 Mpi4 (2001), so I'm rather closly aquinted with the various parts of the cooling system..
The pipe you mention goes from the Thermostat housing to the EV, to return coolant to the EV (to release over pressure I presume), the actual over flow is a simple hole in the top of EV, next to the cap, which exits under the 'flap' on the wing side of the EV. Any liquid just runs down the EV, and into the engine bay into the O/S wing. I don't think there is a connection for a pipe to guide the liquid away from the bay, or into a seperate container.

Had great fun getting the coolant hose clamp from the hose to the water pump undone, even more fun getting it back on, using ordinairy water pump pliers and cable ties. Much profinity was used, but at least I didn't skin my knuckles, or trapped fingers.
This morning, upon fitting the cleaned EV and final hose connections, refilling the system, and bleeding it, it transpired that the bottom clamp of the little hose had somehow also come undone, and coolant was running out as fast as it could be poured in. With everything in place, there is no way to get at the hose clamp with ordinairy pliers, so I bit the bullet, and bought one of those Flexible Hose Pipe pliers. I hate spanding money on tools that I only use once or twice (don't mind spending good money on good tools that are used regularly), but this is a game changer. Managed to refit the clamp in situ, in 5 minutes.
Car now running fine again.

Edited 15 May15 May by charon

I had a little bit of trouble getting it back in place indeed. But after some swearing, it was done. As far as i can see nothing leaks from there.

Today i lifted the car on jackstands and installed the pressure tester in the expansion tank. It didnt lose pressure inmediatly, so im gonna leave it there until tomorrow, with the undertray removed and a cardboard placed underneath to see if any coolant gets there.

I attach a couple of photos i took in the process (sorry for the bad quality, i was on the floor, holding the phone with one hand and a light with another 🤣)

As you can see, the coolant is really clean, a little but faded because we are refilling with destilled water, but any sign of oil or debris in there.

As you can see, the coolant level is really low, it didnt give the "low collant" warning, but it was close to it. By the way, the engine is completly cold (didnt started it since yesterday) and when opening the cap, a little bit of pressure was released, does that mean headgastek problems?

The rig im using, as you can see, i gave it around 1.3 BAR.

Gonna leave it there until tomorrow and see what happens.

The oil cap is usually like this, i asked a couple of mechanics, searched the web and even asked the AI about it, the same answer in all: this engines suffer from a lot of condensation inside the engine, and since is always driven in the city at slow speeds, it doesnt have time to dissapear. But i think this could be too much for only condensation. The watery residue is crystal clear by the way, and no coolant residue can be seen but i dont know anymore.

A couple of photos of some connections. I didnt clean them at all, this is his state after all this time.

Another one from under the pump, no visual residue as far as i can see.

Under the radiator bone dry too.

That oil cap looks horrible, that looks worse than just condensation, but I am interrested in what others with more experience with these engines say.

BTW, that looks like the 'temporary' filler cap that you use when the engine cover is removed, because of the quite frankly redicilous way the regular filler cap fits into the cover, and is not actually closing the filler tightly, but kind of hovering above it.

The cap does look a bit worse than just condensation but it may be normal if its only doing very short runs and from the amount of coolant your losing I would expect a lot more emusification if HG had gone. Hopefully you will see some drips by tomorrow.

Alasdair

Of all the mk1 Fabia engines, the 1.4 mpi is the only one that really seems to suffer HG failures.

Fortunately, it's also probably the easiest one to change.

Not saying it definitely is HGF, but it's probably worth doing a CO2 test on the coolant, if you haven't already, to try to detect combustion gases that might explain the pressure when cold.

1 hour ago, Alasdair1 said:

The cap does look a bit worse than just condensation but it may be normal if its only doing very short runs and from the amount of coolant your losing I would expect a lot more emusification if HG had gone. Hopefully you will see some drips by tomorrow.

Alasdair

I'd vote for too much mayo, even allowing for regular short trips.

After a couple of hours, the pressure was down to almost 1 BAR, and no drips in the cardboard.

I also think thats way too much mayo for only condensation, probably a small leak in the headgasket is pushing little by little coolant inside the engine and to the oil.

Tomorrow im gonna check for any drips, and before starting the engine im gonna remove the sparkplugs to see if there is any coolant inside the combustion chamber. just in case.

Luckily, as Breezy_Pete mentioned, changing the headgasket is not that difficult and is cheap enough. Only the gasket itself and new headbolts to not reuse the old ones, anything more?

Yep after looking again reckon its too much for just condensation as Warrior193 said and as your losing coolant and no drips/signs of coolant after pressure test I am afraid the coolant must be going somewhere internal. Dont think you have an oil cooler so probably HG. I would double check for leaks again just in case its not obvious including heater matrix. Alasdair