Suspected blown head gasket: W126

[firlandsfarm]

I'm pretty sure I have a blown head gasket between a cylinder and a waterway (I am constantly topping-up the water but cannot find any trace of a leak and the exhaust is "steamy"). I have put a compression tester on each cylinder but cannot find one with a sharply lower reading than any other.

Probability tells me that if I select a head and lift it I will have a 50% chance that it is the right one however experience tells me that Sod's Law overrides all else. Anybody have any tricks that might help me find the faulty head before I start work?


Farmer

 

[NormanB]

A compression test is not a good way of detecting a defective head gasket.

A better method if you have the kit is to pressurise the water side via expansion tank.

Leaving aside the 'steamy' exhaust, which as you say is sort of flagging up where the water is going, the test above will be more conclusive and expose other possible leakage paths too like cracked hose connection on radiator, hoses various and of course the water pump.

Good luck.

 

[firlandsfarm]

Norman

Thanks for that idea, I have an aircompressor in the farmyard and could probably rig up something using this, an old expansion tank cap, a valve and a pressure gague. Any idea what pressure I should run it up to?

A stupid question if I may! If I have a leak into a cylinder as I suspect how would I tell which cylinder?


Farmer
"There are three easy ways of losing money - racing is the quickest, women the most pleasant, and farming the most certain." (Lord Amherst)

 

[heckflosse]

Try taking out the plugs.

 

[NormanB]

To be honest - I have never done it. But I have seen the kit in my local garage.

I would guess you would want to maintain about 1 bar (15psi) on the expansion tank. You are going to need in addition to your air supply a spare expansion cap to modify with a fitting for gauge, and one for a line for the air feed plus a valve to lock it off.

As HF suggests whip out the plugs if you suspect a leak into the cylinders.

NormanB

 

[cc]

Have you t checked the water pump?

Leakeage is between engine and pump very difficult to see. There is a hole underneath the water pump if humid/little rusty it is the the pump.

When head gasket leaks:
water goes to cylinders and then there is a white smoke in the exhaust or goes to oil and then you can see it in the oil.

Good luck

 

[firlandsfarm]

Heckflosse,
can I just check this? You're suggesting that I identify the cylinder by allowing it to flood with water and spill out of the plughole or dip something down the plughole (in case one or both valves are open and the exhaust and/or inlet port is draining the water away). I thought of that before but then dismissed it for that reason! Is the theory that any water that gets into the engine will soon be boiled off with a long run?

CC,
I do have a white smoke (see original posting re "steamy"), that's why I think it's a blown headgasket.


Farmer
"When buying a used car, punch the buttons on the radio. If all the stations are rock and roll, there's a good chance the transmission is shot." Larry Lujack

 

[mikeanddot]

Hi firlandsfarm,
Simplest 'trick' I know of to detect a blown head gasket is as follows :
Go to your nearest MoT testing garage and ask them to stick the exhaust emission lance ( the gadget they put in the tailpipe when they read the exhaust output for an MoT) in to your coolant expansion tank. This gizmo is incredibly sensitive and will sniff (read) hydrocarbon content in your water, so to speak, immediately! Also, further evidence can be gained by the normal use of this gadget in the tailpipe with the engine warm and running. A high oxygen content shows that excess air is present in the exhaust - as a rough guide, about 6% HC is about right.. Also with the engine running, remove the cap from the expansion tank (take care) and look inside. See any bubbles? Sorry to sound like an 'anorak' but hope this helps you from spending too much money.
Regards, Mike