cracked head/block question

Is there a way to tell which it is? I had recently put on a new headgasket (two recent head gaskets if you actually consider the kms between them to define recent - block and head were planed for the first).

Background: 2.0L 16v volkswagen 9a block. All new cooling system components, still overheating. temp guage goes up just as fast as the spedometer when I make it work (ie. race type conditions). If I drive it easy, it runs hot, but not overheating. I thought originally that my coolant was boiling over and out of the remote reservoir. I've discovered now that air is getting into the coolant system from some where and blowing it all out.

I haven't pulled it apart again yet. I have leak tested. 1 and 3 are good, 2 and 4 are passing air at tdc.

I hope it's the head that's cracked (if anything has to be cracked), as the block was just recently rebuilt ($$$).

If it is the head and you need one, i might have one for you which will probably need a rebuild.

---

rally gods would turn in their graves if they ever knew Lada's were now part of EU rallying!!!

I would bet on the head first. Cracks around the valve pockets into the water jacket are not uncommon for a number of head types.

Cracks may be very hard to spot; they can be very, very thin, but will give the exact symptoms you describe.

When you leak tested, did you get bubbles in the coolant? If so this is a pretty big leak, and I would be suspicious of a leak around the head gasket if you are getting this much air.

Hopefully a VW expert can tell you better where to look for cracks.

Good luck!
Mark B.

Step 1: find replacement stock head (there have been a dozen 16V Passats coming through the Pick and Pull in Edmonton lately) or try here www.airriders.com. Cost should be $100 or less.

Step 2: slap that bone stock untouched junkyard head onto your block and take her for a chew.

Step 3: swap your cams over, have a beer, and send in your entry for Mountain trials.

The odds of the block being cracked are slim to none. The time to swap the head would be less than the time spent dicking around with dye penetrant trying to decide if the cracks around the spark plug holes are within acceptable limits or not.

Maybe your head is warped? That could be causing a reccuring head gasket leak. What are you waiting for, pull that head! Let us know what you find. Did you get the check I sent you?

Oh, did you check/change the thermostat????

Regards,
Mark B.

Just some general remarks..( I absolutley don't work on or claim knowledge of German cars...)

Typically an overheat under heavy load, rather than light use is related to cooling capacity. Plugged radiator is the most common cause. Too small of a radiator can cause this as well.

There is also the very obscure bad water pump. I have repaired several cars with either rotted or missing impellors and a couple that had loose impellors on the pump shaft.

Faulty T-stats are generally shown by always overheating in 5 to 10 minutes of engine running. Completely closed t-stat shows overheat on an idling engine, partially stuck shows under a load situation. Some do stick intermittently though. Lack of a t-stat can also cause overheat under load as the coolant doesn't stay in contact with the radiator long enough to disapate heat.

You can pick up a chemical tester at some parts stores that sniffs exhaust in the radiator. Turns from dark blue to yellow. Lots of instant pressure ( very hard hoses) exhibited shortly after starting can indicate combustion pressure in the cooling system also.

Most machine shops can pressure test a head pretty cheaply. Many cracks are visable to the eye and are near the valve seats. Some heads twist like a propeller rather than warp in a linear fashion also.

A plugged cat, retarded timing, bottom radiator hose sucking closed can also can serious grief. Of course the cracked head, cracked block can happen as well. I think the head/block issues are caused more often by the overheating or freezing than actually being the initial culprit.

These are just the ramblings of an old mechanic...use at your own risk...

Gene

heymagic Wrote:
-------------------------------------------------------
> Just some general remarks..( I absolutley don't
> work on or claim knowledge of German cars...)
>
> Typically an overheat under heavy load, rather
> than light use is related to cooling capacity.
> Plugged radiator is the most common cause. Too
> small of a radiator can cause this as well.
>
> There is also the very obscure bad water pump. I
> have repaired several cars with either rotted or
> missing impellors and a couple that had loose
> impellors on the pump shaft.
>
> Faulty T-stats are generally shown by always
> overheating in 5 to 10 minutes of engine running.
> Completely closed t-stat shows overheat on an
> idling engine, partially stuck shows under a load
> situation. Some do stick intermittently though.
> Lack of a t-stat can also cause overheat under
> load as the coolant doesn't stay in contact with
> the radiator long enough to disapate heat.
>
> You can pick up a chemical tester at some parts
> stores that sniffs exhaust in the radiator. Turns
> from dark blue to yellow. Lots of instant pressure
> ( very hard hoses) exhibited shortly after
> starting can indicate combustion pressure in the
> cooling system also.
>
> Most machine shops can pressure test a head pretty
> cheaply. Many cracks are visable to the eye and
> are near the valve seats. Some heads twist like a
> propeller rather than warp in a linear fashion
> also.
>
> A plugged cat, retarded timing, bottom radiator
> hose sucking closed can also can serious grief. Of
> course the cracked head, cracked block can happen
> as well. I think the head/block issues are caused
> more often by the overheating or freezing than
> actually being the initial culprit.
>
> These are just the ramblings of an old
> mechanic...use at your own risk...
>
> Gene


Thanks, all of the cooling system components have been checked, replaced with spare (used parts), then replaced with new parts....still overheating. I even drilled a 1/16" hole in the thermostat housing after reading online that the t-stat can become airlocked...no change. I had opened the coolant reservoir on several occasions when cold to make sure that coolant was flowing through the overflow hose. Finally, I opened the reservoir when it was hot (I had been avoiding this) and noticed that I had a lot of air in the system, blowing bubbles constantly. The air kept coming no matter how long I played with it (thinking that I was just 'maybe' pushing air out of the system).

I'm taking Tom's advice and just going to replace the head. I'm hoping that there will be no problem with the block. I'm dealing on a factory rebuilt head right now, with OEM gaskets, etc.

Tom, unfortunately I will not be able to do mt.trials due to work commitments, but looking forward to Bighorn (fingers crossed that it happens)

Like i said i have a head which you can have for free. It will need a rebuild however.
Oscar

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rally gods would turn in their graves if they ever knew Lada's were now part of EU rallying!!!

We had a similar problem on our LeMons CRX. Turned out to be a pinched o-ring on the pipe feeding the water pump. Under load, the inlet to the water pump would pull enough vacuum to suck air into the pump, causing bubbles we thought were a cracked head.

The chemical test on the water showed it was a head gasket, but it wasn't.

At low rpm, when the intake pipe wasn't under suction, it would leak slowly enough that the water evaporated before hitting the ground, so we never saw it.

Your weak compression in 2 and 3 suggest it is a head, and I don't know if VWs have a similar water pump inlet, but if they do, I'd check it.

-Dave

Thanks Oscar, I might take you up on that yet.

Dave, that's great advice (I'm a fan of SCC, btw). I'm not sure that's the problem in this case. I've resolved to replace the head and see what happens.



Edited 2 time(s). Last edit at 06/01/2008 11:28AM by C LePoudre.

> At low rpm, when the intake pipe wasn't under
> suction, it would leak slowly enough that the
> water evaporated before hitting the ground, so we
> never saw it.

I don't get this bit.. maybe it just wasn't leaking at low rpm? Or was there a noticeable problem at low RPM?

---

Andrew M
Onterrible
30ish

Double-check your head gaskets to see if they are right. It has been known for small changes to be made from year to year in heads, blocks, and the gaskets, which make things not line up quite right when mixing different year items. Not likelybut just one more thing to make sure is OK.

Hope you get it fixed this round!
Mark B.

My thought process was to throw a junkyard head (complete with cams, etc.) on to see if that solved the problem before dropping $1500 on a factory rebuilt head. Even with a new head gasket that could be done for under $200 easy. If the replacement head was in decent shape, and the problem was fixed, you could just swap your cams over and be done with it. I'd hate to see you spend mucho $$ on a spiffy chunk o' metal only to find out that wasn't the problem after all.

tmachnik Wrote:
-------------------------------------------------------
> My thought process was to throw a junkyard head
> (complete with cams, etc.) on to see if that
> solved the problem before dropping $1500 on a
> factory rebuilt head. Even with a new head gasket
> that could be done for under $200 easy. If the
> replacement head was in decent shape, and the
> problem was fixed, you could just swap your cams
> over and be done with it. I'd hate to see you
> spend mucho $$ on a spiffy chunk o' metal only to
> find out that wasn't the problem after all.
>
>
That's what I intended, but then found a rebuilt head with gaskets, etc for only slightly more than the $200 range...but not a done deal yet.




Edited 1 time(s). Last edit at 06/01/2008 05:01PM by C LePoudre.

hudson Wrote:
-------------------------------------------------------
> > At low rpm, when the intake pipe wasn't
> under
> > suction, it would leak slowly enough that
> the
> > water evaporated before hitting the ground,
> so we
> > never saw it.
>
> I don't get this bit.. maybe it just wasn't
> leaking at low rpm? Or was there a noticeable
> problem at low RPM?
>
>
> Andrew McNally
> Hamilton ON
> 28

We're still talking about the Honda?
If so, the problem was at the inlet to the water pump. Being part of the cooling system, it was under pressure, and with a pinched O-ring water leaked out. The o-ring was on the back of the engine under the *gasp!* carburetor, so you couldn't see it pissing, and the water evaporated before it could hit the ground, so there was no puddle. Plus, no antifreeze is allowed in LeMons (since ALL fluids end up on the racetrack sooner or later) so you couldn't smell it either.

At high rpm, the water pump is pulling water in so fast it actually sucks air bubbles in past that o-ring (either it pulls enough of a vacuum to overcome the system pressure, or there's some kinda ventrui effect past he o-ring, I dunno).

So the car lost water no matter what, but in the diagnostic process, we saw bubbles in the radiator whenever we revved it up, and concluded (incorrectly) that the higher cylinder pressure at high rpm was causing combustion gasses to leak past the head gasket (and later an imaginary crack in the head), forcing us to spend $37 on a new junkyard head (half price day!) and spend at least 45 minutes swapping it.

We got really good at swapping Honduh heads...

-Dave