coolant level warning

[ALAN1968]

hi i own a 2010 (60plate) octavia vrs tdi. which has done 80,000 miles, but the coolant level warning keeps coming on. if i take expansion bottle cap off to release the pressure the coolant level comes back up. after a few miles driving it happens again . temperature does not rise above 90 and it's not boiling up. the oil is clear of sludge and i cannot see any leaks. i only did an engine service on 8th Sept and have had this problem ever since. i did not do anything to the coolant system when servicing the engine. engine oil flush, then oil and filter changed 5w 30 fully synthetic, new fuel filter and air filter. surely it's only coincidental that i have this coolant problem. anyone experienced this or knows of a common reason for it. 

Edited 15 September, 2017 by ALAN1968

[TheClient]

Is the coolant level definitely off the bottom of the prongs. A fairly common problem is the prongs get furred up and give false low level readings. You can scrape them with a long screwdriver if the level is still touching them.  This is more commonly observed when the engine is cold started first thing in the morning though.

[ALAN1968]

prongs are clean. level does drop but comes back up when i release the pressure by undoing the cap.

[pikpilot]

Coolant is not compressible so as the pressure rises it must a gas or air that is being compressed to a lower volume.

Best guess is that you have air in the system that needs to be bled out.

 

Worst case Is that you have gasses getting into the coolant circuit from the head gasket or, perhaps some other part that is coolant cooled- is the EGR valve cooled by coolant or oil? I can't remember.

[Ardle]

Is it wise or good practice to use an engine flush on oil change!? Never did and if I remember I read/heard some negative stuff about such a practice before........

[pikpilot]

15 minutes ago, Ardle said:

Is it wise or good practice to use an engine flush on oil change!? Never did and if I remember I read/heard some negative stuff about such a practice before........

 

 

Suggest you repost this question as a new thread. You will get more answers

[FatblokeVRS]

A fault with the pressure cap maybe? Possibly creating too much pressure in the expansion bottle.

Try that first. A new cap should only be a few pounds.

 

[ALAN1968]

tried a cap from a vw golf that runs fine. i have still got the problem and the golf ran fine with my cap on. 

[ALAN1968]

10 hours ago, Ardle said:

Is it wise or good practice to use an engine flush on oil change!? Never did and if I remember I read/heard some negative stuff about such a practice before........

i feel that in my case it was not a good idea. I have used a draper expert combustion gas detector kit borrowed from a friend. an easy to use piece of kit, but it's telling me i have combustion gases getting into coolant system. which is telling me a possible head gasket problem. i am now thinking that a previous owner may have used an additive to cure a head gasket leak and then me flushing the engine has removed tha additive repair. 

[ALAN1968]

On 15/09/2017 at 15:32, pikpilot said:

Coolant is not compressible so as the pressure rises it must a gas or air that is being compressed to a lower volume.

Best guess is that you have air in the system that needs to be bled out.

 

Worst case Is that you have gasses getting into the coolant circuit from the head gasket or, perhaps some other part that is coolant cooled- is the EGR valve cooled by coolant or oil? I can't remember.

after doing a combustion gas detector test, it is giving a positive result for possible head gasket leak.  

[Ardle]

23 hours ago, Ardle said:

Is it wise or good practice to use an engine flush on oil change!? Never did and if I remember I read/heard some negative stuff about such a practice before........

 

23 hours ago, pikpilot said:

 

 

Suggest you repost this question as a new thread. You will get more answers

I kinda new the answer, and was just pushing op Alan in that direction, breaking it gently as such. But thanks anyway :-)

[ALAN1968]

car all sorted now after adding a simple bottle of K SEAL.  brilliant stuff. 

[Ardle]

2 hours ago, ALAN1968 said:

car all sorted now after adding a simple bottle of K SEAL.  brilliant stuff. 

Brilliant, sounds like you reversed the damage cool...

[Ootohere]

Not really sorted, just the leak now blocked by a chemical reaction between the K-Seal & Air.

Does the job but really it would be better to find the leak & resolve / fix the fault.

So a common bodge, usually carried out before selling on / trading in a vehicle.  Buyers beware.