australia:car_headgasket
combustion leak / head gasket leaking
Introduction
failure of the sealing at the head gasket may result in:
combustion gases leaking into the coolant system
this is evidenced by air bubbles rising up when the radiator cap is off and the engine is started
it can be proven by using an Head Gasket Test Kit analyser which changes color if the bubbles are exhaust gases
coolant leaking into the combustion chamber causing:
-
white smoke (if using anti-freeze) / steam from exhaust
water in cylinders or on spark plugs when you pressurise the coolant system
cylinder misfiring due to transient spark plug issues
possible leaking of coolant into the engine oil
definitive repair is VERY EXPENSIVE (thousands of dollars - parts alone will approach $AU1000) as it usually requires removing the whole engine and thus on an old car this may not be cost effective
an alternative is to try repair using head gasket sealants which are poured into the radiator and which then hopefully solidify in the head gasket crack and stop the leak (see below)
Diagnosis of a combustion leak / head gasket leak
there must be unexplained coolant leak
there should be exhaust gases escaping into coolant and coming out of radiator when cap removed
severe leaks may also cause:
a leak allowing mixing with oil will additionally show:
foamy/milky oil (although this can occur at places other than the head gasket)
Possible causes of failed sealing of head gasket
cracked head gasket as a result of prior over-heating (eg. stuck thermostat)
warped engine from overheating (even one thousandths of an engine warp will create sufficient leakage at the gasket)
cracked engine head
cracked intake manifold gasket
Gasket sealant repair options
these are generally based upon using sodium silicate products (+/- other additives such as microfibres)
the sodium silicate hardens in areas of high temperatures (eg. 1000deg) such as at the gaskets to hopefully form a seal which is generally temporary although additional additives aim to provide a more long lasting seal (at the added risk of clogging up the thermostat and radiator, and possibly the oil and oil filter)
thus generally the engine needs to be run at optimum temperature for these products to work and a second application may be required
follow the instructions carefully
choose product taking particular note of the recommended idle time required and whether your car can go that long
consider what they are made of and risk of clogging coolant system / heater core:
sodium silicate only eg. Blue Devil
sodium silicate with fibres
copper with ceramic fibres without silicate
you may need to flush the coolant system first esp. if it is dirty or you are using a silicate sealant
silicate sealants work best in clean water as the coolant and work best after a few hours of flushing the coolant system
1)
shake well before pouring
make sure before adding sealant, radiator fluid is above internal radiator core
generally pour into radiator, top up coolant if needed, then start engine and turn heating system and fans all the way up
usually run for 15 minutes until it gets to optimum operating temp so thermostat opens and the sealant can get to the gaskets and they are hot enough to alter the sealant - usually 105degC, then turn off to cool it down and leave for a few hours or overnight so the coolant can solidify in the gasket
some recommend repeating this 15minute idle then several hours cooling several times if using a silicate sealant and for bad cases consider removing the affected sparkplug to reduce pressures while it is sealing
2)
take great care on 1st run to ensure it doesn't over-heat due to clogged thermostat
microfiber options
australia/car_headgasket.txt · Last modified: 2022/03/20 17:07 by gary1