what's the deal with "head gaskets"

londonTiger

I used to read about head gaskets failures and stuff, and apparntly how much of an expensive repair it is.

I didn't know what a head gasket was - I assumed it was an integral part or moving part of the engine. Like some big part on a piston or cylinger or something.

Then I find out that a head gasket is just a rubber seal inbetween the head and the block to prevent leaks I assume.

So why is this repair so expensive? Why are "blow gaskets" such a big problem? Surely any DIYer is able to remove the head and replace the gasket with a new one?

Talking of which my car has done 100K and I presume a lot of stuff like the lambda sensors, head gaskets, gear oil and other stuff need changing. What's the rough mileage for head gasket replacements?

madtrekker

I'm no mechanic (far from it) but I think the problem is not the seal itself needing replacing but the fact that when it goes, steam / water gets into the engine or bits where it's not meant to go, and bu**ers it up. So the true cost is replacing the engine.

colino

The head gasket is just a seal between the cylinder block and the cylinder head. It can be very simple or a complex, multi-part gasket with different components. In very basic car, it is a doddle to do. Unfortunately very basic cars tend to have pretty unstressed engines and the head gasket isn't a regular job.
With complex, multi-valve, over head cam plus perhaps balancer shafts and multiple heads (V and Ws), it becomes more of a mine field for the avaerage punter to know how to take it apart properly and rebuild successfully.
In short, the cost isn't the head gasket, it is the considerable labour costs involved that makes it expensive.

londonTiger

Oh OK. So I presume if you were to add head gasket replacement into the long life service. It should come up to a reasonable £50 or something? rather than £500?

GlynD

A Head Gasket isn't made of rubber. It's usually made of metal and is designed to seal the joint between the cylinder head and the short motor. If there is a failure of the head gasket there will usually be an escape of hot exhaust gasses which burns and erodes either the machined surface of the head or the engine block meaning that, even with a gasket, the joint can't be sealed and will require the damaged surface to be refaced.

The reason it costs so much to repair a head gasket is the time to remove all the gubbins from the top part of the cylinder head to get at the area and of course to replace it once the new gasket has been torqued into place.

No easy job.

There's no rough mileage for a HG replacement. If the engine never overheats the gasket can, quite feasibly, last for the the life of the engine.

Foxy-Stoat_3

HG is the piece of material that seals the head to the block. Its not a nice job, very time consuming and easy to get wrong and difficult to do properly for a diyer. Under normal driving conditions with proper maintenance then the HG should last as long as you own/drive the car, unless you own a Freelander/MGF some Camry's and others.

HG's normal go when the user doesn't check coolant levels or drives while the engine is overheating or if the water pump fails or more commonly/easy fix if the thermostate sticks.

Cause for overheating or low/no coolant are many:
Leaky hoses
Leaky/failed water pumps
Leaky radiator
Failed radiator cap
Improper maintenance
Wrong mixture of coolant/water
Failed water seals
Failed thermostate

Other symptoms:
You are the owner/driver of a Freelander
You are the owner/driver of a MGF

other makes and models have common HG failures.

GlynD

Foxy-Stoat wrote: »

Other symptoms:
You are the owner/driver of a Freelander
You are the owner/driver of a MGF

other makes and models have common HG failures.

I was that soldier

mattyprice4004

madtrekker wrote: »

I'm no mechanic (far from it) but I think the problem is not the seal itself needing replacing but the fact that when it goes, steam / water gets into the engine or bits where it's not meant to go, and bu**ers it up. So the true cost is replacing the engine.

Wrong. It's not a cost of replacing the engine at all - sure, other things may get contaminated when the oil/water mix and this needs to be flushed out, but it's nowhere near an engine change.

Usually it's good practice to replace the thermostat and water pump, but aside from that a good cleaning is all everything needs.

londonTiger wrote: »

Oh OK. So I presume if you were to add head gasket replacement into the long life service. It should come up to a reasonable £50 or something? rather than £500?

No. You have to remove the inlet / exhaust, cambelts, lots of ancillaries etc. It's a good 4-6 hour job on most cars, plus an oil and coolant change plus the parts mentioned above.

Foxy-Stoat wrote: »

HG is the piece of material that seals the head to the block. Its not a nice job, very time consuming and easy to get wrong and difficult to do properly for a diyer. Under normal driving conditions with proper maintenance then the HG should last as long as you own/drive the car, unless you own a Freelander/MGF some Camry's and others.

HG's normal go when the user doesn't check coolant levels or drives while the engine is overheating or if the water pump fails or more commonly/easy fix if the thermostate sticks.

Cause for overheating or low/no coolant are many:
Leaky hoses
Leaky/failed water pumps
Leaky radiator
Failed radiator cap
Improper maintenance
Wrong mixture of coolant/water
Failed water seals
Failed thermostate

Other symptoms:
You are the owner/driver of a Freelander
You are the owner/driver of a MGF

other makes and models have common HG failures.

If you have any MG/Rover with the K series engine, you'll always be told you have HGF, it's going to happen etc etc.

It's simply not true - many go on for 100k+ and are scrapped on their original gasket.
If they do go and the replacement is done properly, it shouldn't go again. They key is to fix the issue that caused the gasket to fail in the first place.

The problem with the Rover K series is the very small coolant capacity, a small leak can soon empty the cooling system, leading to HGF.

Foxy-Stoat_3

Oops, bit slow in replying.

On an un-opened engine you should adopt the, if its not broken, don't fix it method.

Preventative maintenance for a HG is making sure the coolant system is working properly and correctly. Temperature needle in the gauge should sit in the middle, unless you have a stooopid newish BMW where the did away with the temperature gauges!!!!! Replace the water pump when cambelts are changed making sure the radiator fans kick in when they should.

I would replace the thermostate with coolant changes and inspect radiator and coolant hoses and leaks on the garage floor/drive etc etc.

What car have you got? There may be known/common faults that occur. For example my old 18 year old MR2 turbo that had over 150,000 miles on the clock running 1 bar of boost was brought down by a tiny rubber seal on the radiator that was perished and letting in air into the system that costs a few pence to fix, but caused untold amounts of issues until I found the fault.

Foxy-Stoat_3

mattyprice4004 wrote: »

Wrong. It's not a cost of replacing the engine at all - sure, other things may get contaminated when the oil/water mix and this needs to be flushed out, but it's nowhere near an engine change.

Usually it's good practice to replace the thermostat and water pump, but aside from that a good cleaning is all everything needs.



No. You have to remove the inlet / exhaust, cambelts, lots of ancillaries etc. It's a good 4-6 hour job on most cars, plus an oil and coolant change plus the parts mentioned above.



If you have any MG/Rover with the K series engine, you'll always be told you have HGF, it's going to happen etc etc.

It's simply not true - many go on for 100k+ and are scrapped on their original gasket.
If they do go and the replacement is done properly, it shouldn't go again. They key is to fix the issue that caused the gasket to fail in the first place.

The problem with the Rover K series is the very small coolant capacity, a small leak can soon empty the cooling system, leading to HGF.

And many don't reach 30,000 miles until the HG let go which is a joke.

Take a look how many are for sale on some online auction sites for spare/repairs with HG issues, same goes for Freelanders...they all seem to be on 60,000 miles with a new headgasket just fitted. Installs nothing but confidence...NOT

worried_jim

My Rover 214 HG went. £350 repair back in 1997, never drove the same after and offloaded the car part ex for a Celica. Wouldn't touch a K series engine again with a barge pole.