how can a BHG cause overheating?

[SL666]

It seems every time someone says their car is overheating, someone suggests they have a BHG, i can't see how this is possible, can someone please explain it to me.

I'm not talking about when a BHG leaks all the coolant out and the car overheats, or pushes all the coolant out of the overflow, these are both obvious symptoms.

[Norbie]

If the gasket is leaking combustion gases into a water jacket, overheating is one of the first symptoms. You end up with big air pockets in the system which greatly reduces the effectiveness of the cooling system.

Of course the gasket might blow near an oil gallery in which case you won't get overheating symptoms.

[JustCallMeOrlando]

Or in my case it'll just burn coolant and not overheat either

[mtp_69_i]

Mine leaks coolant out but nothing into the combustion chamber or oil galleries so all it does do is get hot.

Still drives fine, just have to top it up every now and then.

[SL666]

If the gasket is leaking combustion gases into a water jacket, overheating is one of the first symptoms. You end up with big air pockets in the system which greatly reduces the effectiveness of the cooling system.

Of course the gasket might blow near an oil gallery in which case you won't get overheating symptoms.

or if its a gemini it will blow between cylinders..

I understand that happens (must be a peculiar to particular engines to overheat in these circumstances) but its still going to be using water, or pushing water into the overflow, etc etc, in my experience it will also stumble on at least one cyl when you try to start it in the morning.

I tend to find though that a BHG is moreoften caused by overheating, warping the head and decreasing the squish on the gasket..

It just seems to be that in any thread here about overheating, the finger always gets firmly pointed at a BHG, when i would think that would be one of the last places to go looking? or one of the easiest to dispell? I'm worried that noobs might be getting ripped off by workshops because they drop their cars in saying 'its got a blown headgasket' or they pull them apart and don't know what to look for to be able to tell that its definately there. (or the gasket gets destroyed when you pull the head off)

[MR 1JZ]

It seems every time someone says their car is overheating, someone suggests they have a BHG, i can't see how this is possible, can someone please explain it to me.

I'm not talking about when a BHG leaks all the coolant out and the car overheats, or pushes all the coolant out of the overflow, these are both obvious symptoms.

people always suggest that becuase they are used to the 7M threads

[Admiral coFF33]

^^ LOL

Seems like supras and soarers and the BHG all go together like a loving family

[haison]

Amen.
(10chars)

[oldcorollas]

It just seems to be that in any thread here about overheating, the finger always gets firmly pointed at a BHG, when i would think that would be one of the last places to go looking? or one of the easiest to dispell? I'm worried that noobs might be getting ripped off by workshops because they drop their cars in saying 'its got a blown headgasket'

well.. it's one of the more serious issues that could cause overheating, and lcukily enough, one of the easiest to dispel.. so it';s better to check for it first and prevent further damage.

however, some people just latch onto one thing and suggest it to everyone.. such is the nature of internet learning.

[MR 1JZ]

such is the nature of being teh intarwebs mechanikz!

fixed for you

[Jorrs]

If the gasket is leaking combustion gases into a water jacket, overheating is one of the first symptoms. You end up with big air pockets in the system which greatly reduces the effectiveness of the cooling system.

Of course the gasket might blow near an oil gallery in which case you won't get overheating symptoms.

yes thats what happened to mine, i didnt have any overheating issues, just oil in my coolant and vice bersa.

[Joshstix]

There is also the fact that all the basics that tend to cause overheating problems tend to be extremely reliable with Toyota's in general and a large percentage of over heating Toyota's are caused by blown head gaskets.

[SL666]

There is also the fact that all the basics that tend to cause overheating problems tend to be extremely reliable with Toyota's in general and a large percentage of over heating Toyota's are caused by blown head gaskets.

I dissagree, most overheating questions on here are about "ive just bought this car, and it does this" or "i've just put a twin turbo 1u into a toyota stout and it seems to be cooking"

its unusual to see one with a 'as factory' car.. and i would still dispute that the majority of those would be caused by a BHG, or even anything vaguely related.

[mtp_69_i]

I dissagree, most overheating questions on here are about "ive just bought this car, and it does this" or "i've just put a twin turbo 1u into a toyota stout and it seems to be cooking"

its unusual to see one with a 'as factory' car.. and i would still dispute that the majority of those would be caused by a BHG, or even anything vaguely related.

check out my for sale thread sometime

bone stock ST162 celica with a leaky head gasket.

[SL666]

chemi-weld worked on the excel i flogged to work and back for ages.