Coolant Leakage Issue

[srane4213]

I have a similar issue on my Octy 1.9 Tdi Alh 
Initially I was loosing coolant and a alarming range, I had to top up the expansion tank every 15-20 kms. (The car was not overheating at this point)
I got the radiator opened and cleaned and it was almost 50% blocked. The issue still persisted after this, so I checked the thermostat and it was stuck in closed position even in boiling water. As a temporary fix while I waited for the new thermostat to arrive, I went ahead and ran the car without the thermostat for a few days. The conditions were better for a few days initially and the car stopped overheating (the car ran a lot cooler than it was supposed to though). This might be because of coolant getting circulated even without the reaching the desired temp.
But even then I had to refill the coolant after 350-400 kms. So I suspected the heater core as I could feel the passenger side carpet and it was wet most of the time (Got to know later on that the door seal was leaking).
After this I bypassed the heater core for testing purposes, and still I was loosing the coolant but not at a very high rate (car was overheating sometimes randomly). I had to top it up very 350-400 kms but this time I found oil in the coolant. To tackle this issue I bypassed the oil cooler as well and post this car ran fine in city traffic but used to overheat on highways randomly, but when the 2nd stage of rad fans kicked in the temp. used to come down below the 90 deg. mark on the cluster.
One fine day, the car began overheating in city traffic as well and the temp. warning popped up on the cluster.
Next day I checked the oil filler cap and I could see water in oil. So, changed the Head Gasket, Water Pump, Timing kit, Serpentine belt, got the radiator cleaned again and installed a new oil cooler along with a thermostat. Now after all this, the car runs fine doesn't overheat at all the radiator fans kick in when they're supposed to the AC runs normally. The only thing still bypassed is the heater core and I'm still loosing the coolant every 300 kms or so....I have to top up the expansion tank with approx. 1 Lit. .

Any ideas as to what might be wrong?? 
Sorry for the long post.
TL;DR  Car overheats, changed HG, WP, Refurbished Radiator, New Oil Cooler, New thermostat, bypassed heater core....car doesn't overheat now but still loosing coolant. 

P.S The old head gasket was damaged. If needed I can post a pic.

[kentphil1]

I would be inclined to get the car onto a cooling system pressure tester and see what that yields, including testing the radiator cap itself.

 

You have done the obvious bypasses and diagnostics, time to dig a little deeper.

 

One other thing, you mention that the fans cut in when they should, but are they runing at the low or high speeds?, as the fans have 2 operational speed modes.

Edited 23 December, 2020 by kentphil1

[srane4213]

They run on the low speed mode initially and switch to high speed for a short while on highway runs.....

[Vijay2018]

Have you tried using a UV dye to see if you can find any traces of a leak??

[srane4213]

Guys an update. 
The car overheated yesterday on the highway

I flushed the coolant and changed it again with G12 coolant.....it's not overheating as of now but I have run the car on city roads only after flushing the coolant yesterday. 
Attaching a pic of the drained coolant for your ref.
Also attaching a pic of the engine head which was taken during the HG change. 

[Burhan]

When you changed the gasket, what was your find? Was the gasket blown or not? 

Have you checked whether the engine head or block has warpage?

[srane4213]

1 minute ago, Burhan said:

When you changed the gasket, what was your find? Was the gasket blown or not? 

Have you checked whether the engine head or block has warpage?

I had checked the cylinder head for straightness and it was proper (I don't know the exact terms for these but since I was on a budget I did all these jobs myself) .

Before installing the head, I had cleaned all the oil, coolant passages.
And yes the old HG was damaged. Attaching a pic for your ref.

[srane4213]

Hey Guys, an update....
Was still leaking coolant so decided to have a pressure test done on the cooling system.
The radiator was leaking from a corner....have rectified the issue by repairing the radiator and drove for around 65-70 kms today.....no leakage as of now and the car has not overheated since...….only issue I faced was that the power steering pump hose which runs from the reservoir to the PS Pump was brushing against the fan blade and had developed a hole which was leaking the PS Fluid. 
Luckily had an extra hose in the boot of the car, so changed the leaky hose and topped up the PS Fluid....had to drive the car with very low PS Fluid for around 3 kms till I could find a spares shop topped it up and all is good since.

Will update regarding the coolant leakage issue in a few hundred kms.

[Burhan]

15 minutes ago, srane4213 said:

only issue I faced was that the power steering pump hose which runs from the reservoir to the PS Pump was brushing against the fan blade and had developed a hole which was leaking the PS Fluid. 
Luckily had an extra hose in the boot of the car, so changed the leaky hose and topped up the PS Fluid....

Also look for any damage at the fan blade which was brushing against the hose.

[srane4213]

On 02/01/2021 at 23:00, Burhan said:

Also look for any damage at the fan blade which was brushing against the hose.

the fan blades were not damaged and are working as they should.....however....yesterday on the highway...I was cruising and around 90-100 kmph and I could see the temp gauge needle starting to cross the 90 deg mark.....so I switched off the AC and started slowing down...and the needle went down to the normal position.....Also this was after the car had been running for and hour or so.....and yes there was a little coolant loss.....it was just below the minimum mark on the expansion tank but I didn't get a warning on the cluster....now I'm super confused as to what might be the problem??  

[Burhan]

20 hours ago, srane4213 said:

the fan blades were not damaged and are working as they should.....however....yesterday on the highway...I was cruising and around 90-100 kmph and I could see the temp gauge needle starting to cross the 90 deg mark.....so I switched off the AC and started slowing down...and the needle went down to the normal position.....Also this was after the car had been running for and hour or so.....and yes there was a little coolant loss.....it was just below the minimum mark on the expansion tank but I didn't get a warning on the cluster....now I'm super confused as to what might be the problem??  

 

Looking at your situation you have almost gone through everything which can cause a leakage. Have you tried a dye test ? If yes, have you found any leakage that you can notice on the outside of engine?  if you are unable to figure out leakage till now then it probably is boiling out through overflow spillway of expansion tank.

 

I had the same leakage issue a while ago and the culprit in my case was a carbon deposited 2nd stage fuse connection(Fan Speed) placed above the battery. Try giving a look at the fuse and connections that might cause overheating of the coolant. Coolant loss in such cases happens due to over boiling through expansion tank's overflow spillway.

[Burhan]

Update on my coolant leakage:

 

Since I fixed the fuse "2nd Stage fan speed", I did not experienced engine overheating since then but a while ago I replaced coolant (filled to the mouth) and have noticed decrease in coolant level. The level only decreases till the half way of expansion tank (Near the central seam). Level doesn't decrease beyond that.

Any particular reason for this to happen?

[srane4213]

1 hour ago, Burhan said:

Update on my coolant leakage:

 

Since I fixed the fuse "2nd Stage fan speed", I did not experienced engine overheating since then but a while ago I replaced coolant (filled to the mouth) and have noticed decrease in coolant level. The level only decreases till the half way of expansion tank (Near the central seam). Level doesn't decrease beyond that.

Any particular reason for this to happen?

The coolant level should be between the max and min marks on the expansion tank...... I guess since you had filled more than that...the system might've overflowed and the level must've decreased. I'm just taking a shot in the dark....so idk if I'm right or wrong about this.

Edited 14 January, 2021 by srane4213

[mac11irl]

topup the coolant only to the max line on the expansion bottle. monitor it for a while. 

if you overfill it, it will over pressurize the system when it heats up and expands. the pressure increase effectively lowers the boiling point, so youll then lose even more. 

 

[Burhan]

16 hours ago, srane4213 said:

The coolant level should be between the max and min marks on the expansion tank...... I guess since you had filled more than that...the system might've overflowed and the level must've decreased. I'm just taking a shot in the dark....so idk if I'm right or wrong about this.

 

6 minutes ago, mac11irl said:

topup the coolant only to the max line on the expansion bottle. monitor it for a while. 

if you overfill it, it will over pressurize the system when it heats up and expands. the pressure increase effectively lowers the boiling point, so youll then lose even more. 

 

 

You guys must be right, as the name suggest expansion tank needs some space for liquid to expand when it gets hot. Thats the reason I shouldn't have filed beyond the max marking. 

Edited 15 January, 2021 by Burhan