Poor circulation...

[pj71]

Hi all, hope everyone is doing well. 

I recently bought a 2007 octavia with a 1.9tdi diesel lump. Yes, it's got the dreaded BXE code motor.

My problem is this.. Poor coolant circulation. It's at a trusted workshop,and so far they have replaced the radiator, heater matrix, water pump, flushed the system several times, bypassed the EGR cooler, all to no avail! Does anyone have any ideas as to wtf is going on with this otherwise sound engine. 

Many thanks in advance. 

[Guest]

What makes you think poor coolant circulation?

[pj71]

Hi. The guys doing the work on it for me have done every conceivable test on it.

The heater keeps going hot and cold. 

At first they thought that the head gasket had gone, but further investigation ruled that out. 2 weeks on and several new parts later they still have the same problem. 

The latest idea now is that something is clogging the block water ways, because at some point in this poor car's life some cretin has put something in the coolant to cover up god knows what problem. 

I may have to put a second hand engine in it!

[Guest]

IMO

 

If the workshop was any good they'd have ascertained if there was foreign matter blocking the heater matrix when they removed it and flushed the system, not fire the parts cannon at it unnecessarily.

 

Given the age of the car I suspect bad temperature sensors or connections in the HVAC electrical system.

 

Using diagnostics you can see what all the sensors are reading, unusual values can just be a bad sensor connector due to oxidation/vibration, the sort of issue that can be fixed by (un)connecting the plug several times to refresh the contacts.

 

If the sensors are sending bad signals the heater temperature will be all over the place.

 

Newer cars with electronics can't be diagnosed the same as old technology, the electronics controlling things can lead you down a rabbit hole so it is essential to see what the system is seeing.

[pj71]

Thanks for that. I trust the guys I use,but I will try anything to get this resolved as quickly and cheaply as possible. 

Any and all information is greatly appreciated. 

Thanks.  

[EnterName]

1 hour ago, pj71 said:

Hi. The guys doing the work on it for me have done every conceivable test on it.

The heater keeps going hot and cold. 

At first they thought that the head gasket had gone, but further investigation ruled that out. 2 weeks on and several new parts later they still have the same problem. 

The latest idea now is that something is clogging the block water ways, because at some point in this poor car's life some cretin has put something in the coolant to cover up god knows what problem. 

I may have to put a second hand engine in it!

My knowledge of car heating systems isn't great, but let me throw some thoughts your way.

Firstly, the description of the problem "The heater keeps going hot and cold. " is not particularly helpful.

Can you describe the problem more, give us the conditions under which the symptoms occur, and more details about the symptoms please and your car?

eg:

Do you have full climate control?

Does the problem happen regardless of whether the air-con on and off?

Is the cold air cooled, or just ambient temp from outside?

Are there any unusual noises?

How frequently and for how long does the air change from hot to cold, and  (I assume) vice-versa.

[pj71]

All I know is what I've already stated. 

What I do know is that it has nothing to do with the a/c. The car is the basic ambient equipped model. 

[J.R.]

30 minutes ago, pj71 said:

All I know is what I've already stated. 

What I do know is that it has nothing to do with the a/c. The car is the basic ambient equipped model. 

In which case you have as little to go on as we do.

 

Unless you have no visual or auditory senses you must be able to answer Enternames very sensible and pertinent questions.

 

The problem could well be the well documented Silkat teabag rupture but with only the scant details you are willing to reveal that can only be uninformed speculation.

[Guest]

@J.R.

I'm not sure this applies to the Mk.II

 

From what I've seen it was implemented from the Mk.III 2012- and the coolant reservoir sphere is marked "Mit Silikat" (With Silicate)

 

 

 

Edited 25 May, 2022 by MicMac

[J.R.]

Thanks for that.

 

A sister vehicle but my 2015 Yeti did not have the teabag or any Silkat markings and the reservoir does not seem to be double skinned.

 

Silkat when retained and not allowed to float around the system is supposed to protect the differing metals in the cooling systeml against bveing run without coolant protection, that is precisely what I did for close to 2 years due to my senility yet the plain tap water that came out was clear and unstained so maybe there is Silkat somewhere?

[Guest]

@J.R.

I've read somewhere some VAG models have a silicate store built in to the radiator instead, again newer models and I would treat it as unverified information.

 

I think many Octavia owners need to realise that even the youngest Mk.IIs are now 10 year old technology.

[pj71]

5 hours ago, J.R. said:

In which case you have as little to go on as we do.

 

Unless you have no visual or auditory senses you must be able to answer Enternames very sensible and pertinent questions.

 

The problem could well be the well documented Silkat teabag rupture but with only the scant details you are willing to reveal that can only be uninformed speculation.

I've literally only driven the car once since buying it. The problem arose straight away with an empty expansion bottle after just a 19 mile drive home. I took it straight to the garage where it has been since. 

Sorry if my lack of knowledge isn't enough for an informed opinion, I am now going to consider the matter closed as I am no closer to an answer.

Many many thanks to all you guys on this excellent forum, cheers. 👍  

[J.R.]

Did the heater keep going hot and cold during your 19 mile drive (not surprising with a low water level) or is it now reported by the mechanics after having fired the parts cannon at it?

[Guest]

@pj71

Don't be disheartened, when you get it fixed let us know how.

[EnterName]

1 hour ago, pj71 said:

I've literally only driven the car once since buying it. The problem arose straight away with an empty expansion bottle after just a 19 mile drive home. I took it straight to the garage where it has been since. 

Sorry if my lack of knowledge isn't enough for an informed opinion, I am now going to consider the matter closed as I am no closer to an answer.

Many many thanks to all you guys on this excellent forum, cheers. 👍  

Don't feel that anyone has had a go at you, it's really just a case of trying to give helpful answers and needing more info.

 

When it comes to the air coming into the cabin, there are only limited things your car can do with it.

1) Accelerate it, via the fan(s).

2) Direct and divert it, via a series of flaps.

3) Block it off completely, via the recirculation flap. (My term for whatever it's called.)

3) Heat it up via the heater matrix. (Basically a little radiator)

4) Cool it down via the air-con.

5) Possibly something else I don't know about. Oh yeah! Filter it via the cabin filter.

 

The problem seems to be associated with 3).

The heater matrix works with water from the cooling system. If you have no water in your heater matrix, you won't get any heat.

Likewise if you have a blocked heater matrix; it might have water in it, but the water will be cooled by the airflow, and won't be replenished with new warm water because there's no water flow.

 

You've said you've only driven it once, home and back to the garage, where it's remained. So you've not been able to see any of the effects of the garage's attempted repairs, and the garage has replaced a lot of parts.

It seems like the car was originally losing water "The problem arose straight away with an empty expansion bottle after just a 19 mile drive home."

That's a pretty catastrophic loss of water for a 19 mile journey. There's a cynical part of me that wonders whether there was water in the system in the first place.

There's another part of me that's wondering whether the car is still losing water.

So, given how many parts have been replaced and the flushing that's been done that hasn't solved the problem, I'm wondering if you have a warped cylinder head. 

 

Edited 25 May, 2022 by EnterName

[EnterName]

Did you ever resolve your heater problem, @pj71?

[pj71]

Nah, sadly had to scrap the car