AAZ - Intermittent Overheating, Head Problem?

[Mick & Tracey]

I have an AAZ on my syncro doka (fitted by previous owner). Running an 80' thermostat.

Temperature gauge normally sits just above mid-point (understand this is common for the AAZ). Occasionally it gets to 3/4 and very occasionally goes worryingly high. Problem has existed on and off for a couple of years. No real pattern to when the problem occurs - can be under load, at speed, at idle or once within 2 mins of start-up. Recently (150 miles after having the timing done), the cylinder head hose split. I've noticed that radiator often feels cold when temp gauge shows high temp at engine, and return pipe to thermostat is cold.

Radiator is fine - it's a TD rad, two years old, fitted by Brickwerks. To be doubly sure I've recently had it pressure tested - absolutely clear throughout. Had coolant gas tested - no hydrocarbons present. Thermostat replaced. New header tank cap fitted (proper one from Brickwerks), new water pump fitted. Problem remains.

I'm thinking that it's now pointing to a head / head gasket issue which my local garage reckon is about a five hour job. Before I take the plunge, is there anything else that it could be or is the head the most likely problem?

Thanks for any advice.
Mick

[langb20]

Hey Mick,
how's the water pump? changed that recently? best to make sure that is doing the do, how i don't really know but worth changing every 100k at least, especially when moving from a car to a van where you got a longer loop on the cooling system.
also, strange how the temperature shot up after just 2 minutes one time and overheating is not always related to load, perhaps your fault is electrical. Check connections are good on the sender (which one are you using, the AAZ one - plastic 4 pin, or one off a CS/JK head?) and earths are too, also clean the pcb connector at the back of the dash possibly - meths & a cotton bud usually does the trick.
Are all the pipes getting warm that should in normal operation? air all bled as per the guide in the wiki? how hot is the cab heater air getting - that loop is 'inside' of the thermostat so should be indicating what's coming out of the head warm/hot/too hot to touch?
Perhaps thermostat is also sticking closed, make sure it's fitted right way round he he
good luck,
Brent

[Mick & Tracey]

Have put a new water pump on.
Heater air is fine - hot but not excessive.
Have bled as per Simon Baxter's method (rev & rev)
Could be sender/electrical but I'm mainly thinking it's a circulation problem as the rad is often cold.
Don't think stat is sticking - I've had three in there. First one, I cut out the centre because I thought it was sticking, second was an 88' one, third one is an 80' one. Right way round?? Er I think so, spring end towards the engine, dome towards the radiator?

[langb20]

aye sounds right way round
hmm dunno, bit stumped. my rad doesn't really get that hot either mind you
as far as i'm aware though, if you have a head problem, the coolant will pressurise like crazy so if it's running ok with the cap off (from cold) and not squirting water at you, then can hopefully rule the head out - some good news at least

[jed the spread]

I am just in the process of changing the head on my AAZ, if they can get it done in five hours they are doing bloody well.. Saying that its taking me ages because I have never really done the job before and my mechanical skills are abit basic really.

When you said your hose split how long did you run it with low coolant? did it get really hot before you noticed it had split? have you felt the rad top and bottom to see if there is an airlock? are you getting back pressure (is the expansion tank behind the number plate filling up when the engine is warm?

jed

[Mick & Tracey]

Cheers Jed.

Garage are just going by the standard time quoted in their data sheets. If they do the work, they'll do it inbetween other jobs and give me a reduced rate but as you say it can easily take a lot longer, which is why I was asking for advice whether I've missed anything else before we take the head off.

The split happened one morning on start up and I ran less than a mile. It hadn't got hot. I don't know if it's linked or just one of those faults that occassionally happens.

Have checked for air locks (as did the garage) and bled each time any thing has been refitted. Followed Simon's proceedure (rev and rev, run, bleed again).

Rad is quite often cold all over (other times it's all fine!).

Expansion tank isn't filling up.

[jed the spread]

Well if you have tried everything that you say you have, what else can it be apart from the head/gasket ? I think you might have to give that ago. I thought you might have cooked the head when the hose split but it sounds like it didnt really get that hot. Mine went after the fan belt snapped and I drove it for four miles. You could try popping a couple of bottles of k-seal in and if that stops it it is a head gasket problem for sure maybe? Best see if this would be ok first by someone more mechanical than me

jed

[footstuck]

There was a problem with the presure caps.
If its a black one buy a new VW on for it.
The New ones are mid blue and are worth investing in(about ten quid I think).
They cause bursts if it is not venting.
It may be causing air pocketing in the head
and subsiquent overheat.
As the air pocket increases in size, you get less cooling
and things tend to rapidly get out of hand.
Worth a try If you havn't already done it

Also if the burst was under the fuel filter
Dont read to much into it as the smallest of leaks over 20 years
will tend to swell and soften the hose causing failure.

[Oldiebut goodie]

This may be a red herring (2s/6d a stone, fresh 5 for a pound ) but is the belt setup driving the water pump the right way as I have read several posts where there are two different rotation oriented pumps and so the belt has to be the serpentine setup (long belt) or otherwise.
Might be worth checking.

[Mick & Tracey]

the belt setup driving the water pump the right way as I have read several posts where there are two different rotation oriented pumps and so the belt has to be the serpentine setup (long belt) or otherwise

Interesting. I've only seen belt passing round outside so thought that's the way they all were. Any idea if this applies to diesels or petrol? Any chance you could give a link to the posts?

[langb20]

my AAZ engine belt passes this way (it came like this so I fitted the new belt the same way):


as far as I'm aware the pump should turn this way (red arrow) when looking through the thermostat hole:


I may have just contradicted myself there, but no overheating problems so far (touch wood)
more confusion: http://www.brick-yard.co.uk/forum/overh ... 48008.html

For my 1Z tdi conversion I am going to run this setup: http://www.brick-yard.co.uk/forum/tdi-w ... KW=#486085 just got to make sure you have the right pump for the engine it seems. I'll have a look at a few more old pumps to check the impellers
gotta love google: http://wiki.answers.com/Q/What_is_the_d ... p_impeller

so if it's going the wrong way, any kind of load on the engine will make it overheat seems to be the conclusions
sorry for lazyness of links

[sciroccotune]

The belts on my 1y are as your top picture, if you have a smooth pulley the belt runs on the smooth side, ribbed = ribbed side.

I guess you may have got the water pump mixed up at some point? Likely caused by a well knows European car part seller

[Mick & Tracey]

langb20

Thanks for the links - reckon I'm ok as I've got Brickwerks pump & housing running clockwise with V-belts

[langb20]

cool (no pun intended)
glad to hear it