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does aaz head usually deform after overheating?
by
vako
on 07 Oct, 2011 11:06
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i have some unusual overheating issues after off road challange. everything worked well during the competitoin itself but after the coolant cooled down and i started the engine thermostat refused to open at all... i drove almost 20 kilometers at 100-110C' before i got home, it was a descent so the water did not boil at all. after many unsuccesfull attempts of opening the termostat i have boiled the water for several time, but as son as i was seeing the water boiling i stopped teh engine and waited for it to cool down. i have changed the thermostat but now i still have the same problem, bottom of the radiators is ice cold....
this evening i when i removed dipstick for the firs time i have noticed a tiny water drops on it, but no foam or something else. there was no foam on filling cap too.
i know that 1.9td head gasket cost only 25 dolars here in georgia but aaz head costs almost 200$....
is head deformation or cracking common for aaz engines?
i have not run it on excessive boost or excessive fuel/air mixture
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#1
by
rodpaslow
on 07 Oct, 2011 13:58
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I've had a coolant hose bust and all coolant run out. At that point the head is toast-warped and cannot be straightened to use. I don't know how hot you let it get, but if you have water in your oil you have a head gasket that needs changing and at that point you can check the head for flatness.
If used within operating temps, I have not seen a VW head warp, even under heavy boost.
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#2
by
vako
on 07 Oct, 2011 14:08
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I've had a coolant hose bust and all coolant run out. At that point the head is toast-warped and cannot be straightened to use. I don't know how hot you let it get, but if you have water in your oil you have a head gasket that needs changing and at that point you can check the head for flatness.
If used within operating temps, I have not seen a VW head warp, even under heavy boost.
after coolant hose burst you had to change the had yes?
there was some air in system during when i firs found out thermostat was not workin (air bleeeding is nesecxary in my car eery time i add coolant.) but there always was water in the system, not less than 4-5 liters. and it did almost not work when the water was boiling, i was stopping the engine every time i niticed it (i know that it is not recoemended to shut down boiling engine but when thermostat is'nt working it is the only wy to cvoll the negine down..
)
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#3
by
vako
on 08 Oct, 2011 14:57
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i have driven 15 kilometers today without thermostat and it does't overheat at all. no oil in coolant or vice versa , but there are bubbles in radiator..... tomorrow i will test it on cold engine.
can it be a head gasket or the head is gone?
if it's the head i will drive for a while like this and take care for it on winter holidays
it's me on the right (3rd place) good result for the first competition (off-road gps orienteering) with my car
Uploaded with
ImageShack.us
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#4
by
vako
on 10 Oct, 2011 00:26
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#5
by
Mark(The Miser)UK
on 10 Oct, 2011 01:53
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i have some unusual overheating issues after off road challange. everything worked well during the competitoin itself but after the coolant cooled down and i started the engine thermostat refused to open at all... i drove almost 20 kilometers at 100-110C' before i got home, it was a descent so the water did not boil at all. after many unsuccesfull attempts of opening the termostat i have boiled the water for several time, but as son as i was seeing the water boiling i stopped teh engine and waited for it to cool down. i have changed the thermostat but now i still have the same problem, bottom of the radiators is ice cold....
this evening i when i removed dipstick for the firs time i have noticed a tiny water drops on it, but no foam or something else. there was no foam on filling cap too.
i know that 1.9td head gasket cost only 25 dolars here in georgia but aaz head costs almost 200$....
is head deformation or cracking common for aaz engines?
i have not run it on excessive boost or excessive fuel/air mixture
More doom and gloom.
Very likely thermostat failed and then engine 'overheated' due to the loading, but probably just blew the gasket due to loading; ie from cylinder pressure, but not from the 19psi or so of the water [filler cap release pressure].
As long as cold water wasn't added to the engine whilst hot, a new gasket should do it.
How old was the old gasket?
I drove towing a caravan with little or no water for 2 miles, with no issues other than the blown gasket, due to a presumably already slightly warped head but mainly a corroded old gasket. I did skim as it was about 4 thou and thus on the limit.
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#6
by
92EcoDiesel Jetta
on 10 Oct, 2011 07:35
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.....
As long as cold water wasn't added to the engine whilst hot, a new gasket should do it.
I often wondered about this. When you add water to the expansion tank globe, doesn't the water go to the bottom of the engine (thermostat housing?) first and not the head? Unless the coolant is completely gone and you have severely overheated the block and head, adding water shoud not do any damage? If on the other hand, when you add the water and you hear cracking and sizzling sounds......hmmmn not good.
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#7
by
Mark(The Miser)UK
on 10 Oct, 2011 08:13
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.....
As long as cold water wasn't added to the engine whilst hot, a new gasket should do it.
I often wondered about this. When you add water to the expansion tank globe, doesn't the water go to the bottom of the engine (thermostat housing?) first and not the head? Unless the coolant is completely gone and you have severely overheated the block and head, adding water shoud not do any damage? If on the other hand, when you add the water and you hear cracking and sizzling sounds......hmmmn not good.
Agreed, adding cold water to a system that has plenty of water, ie just topping up with a pint or so is fine.
Just not when as you say engine is so hot it's ticking, and water level out of view...
I was nearly spreading my own 'doom and gloom' then... 
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#8
by
vako
on 10 Oct, 2011 13:09
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i have some unusual overheating issues after off road challange. everything worked well during the competitoin itself but after the coolant cooled down and i started the engine thermostat refused to open at all... i drove almost 20 kilometers at 100-110C' before i got home, it was a descent so the water did not boil at all. after many unsuccesfull attempts of opening the termostat i have boiled the water for several time, but as son as i was seeing the water boiling i stopped teh engine and waited for it to cool down. i have changed the thermostat but now i still have the same problem, bottom of the radiators is ice cold....
this evening i when i removed dipstick for the firs time i have noticed a tiny water drops on it, but no foam or something else. there was no foam on filling cap too.
i know that 1.9td head gasket cost only 25 dolars here in georgia but aaz head costs almost 200$....
is head deformation or cracking common for aaz engines?
i have not run it on excessive boost or excessive fuel/air mixture
More doom and gloom.
Very likely thermostat failed and then engine 'overheated' due to the loading, but probably just blew the gasket due to loading; ie from cylinder pressure, but not from the 19psi or so of the water [filler cap release pressure].
As long as cold water wasn't added to the engine whilst hot, a new gasket should do it.
How old was the old gasket?
I drove towing a caravan with little or no water for 2 miles, with no issues other than the blown gasket, due to a presumably already slightly warped head but mainly a corroded old gasket. I did skim as it was about 4 thou and thus on the limit.
i dont think that the gasket is ever changed on my engine
but i have two more questions, is it possible for metal aaz headgasket to fail? and if the headgasket or the head is blown wouldnot i have more gasses in cooling system then it is on my video, which i shot this morning?
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#9
by
vako
on 10 Oct, 2011 13:17
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and the last question for today
if hg has only a tiny leak of exhaust in coolant will i harm the engine if i drive like that for a few months
? without a thermostat temperature doesn't go up even to 70-80 degrees, no matter how hard i push it.
p.s. i have japaneese style cooling system now. with radiator cap and external expansion tank (like on suzukis and hondas)
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#10
by
R.O.R-2.0
on 10 Oct, 2011 14:35
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it could erode the metal of the head casting if you leave it too long.
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#11
by
vanbcguy
on 11 Oct, 2011 09:42
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Biggest problem will be that one day when you're pushing the car REALLY hard, months from now and it lets go a bit more. Thing is you never know when that day will be, so you will always have it in the back of your mind, bugging you while you drive (or at least I would!!)
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#12
by
vako
on 11 Oct, 2011 15:09
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Biggest problem will be that one day when you're pushing the car REALLY hard, months from now and it lets go a bit more. Thing is you never know when that day will be, so you will always have it in the back of your mind, bugging you while you drive (or at least I would!!)
it could erode the metal of the head casting if you leave it too long.
thanks for the replies , as i can see nothing fatal will happen to my engine if i drive like this for 3-4 months. there are only tiny bubbles in coolant when i'm reeving engine up to 3000-3500. and i'm not 100% sure that it is combustion gasses. i plan on rebuilding my engine next summer (tdi style spocket, new bearings all around and other small things), and now i push it hard only when it is very very necessary
other than that i'm balanced and economical driver
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#13
by
Mark(The Miser)UK
on 11 Oct, 2011 15:25
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Biggest problem will be that one day when you're pushing the car REALLY hard, months from now and it lets go a bit more. Thing is you never know when that day will be, so you will always have it in the back of your mind, bugging you while you drive (or at least I would!!)
it could erode the metal of the head casting if you leave it too long.
thanks for the replies , as i can see nothing fatal will happen to my engine if i drive like this for 3-4 months. there are only tiny bubbles in coolant when i'm reeving engine up to 3000-3500. and i'm not 100% sure that it is combustion gasses. i plan on rebuilding my engine next summer (tdi style spocket, new bearings all around and other small things), and now i push it hard only when it is very very necessary other than that i'm balanced and economical driver
Spot on 
Those bubbles could be localised boiling in the head at those rpms. If you can do a journey without coolant loss then carry on
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#14
by
nathan_b
on 11 Oct, 2011 17:27
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100c is not hot, 110c in higher, but OK,
mk4s can go up to 115c before the temp gauge budges from the center perch.
