Testing for blown head gasket
Discussion
Opinions please from those who know far more than I:
What value does an emissions test have in determining whether a head gasket has gone? My garage missed the problem in my MG despite doing this test (and bizzarely still stand by this method, despite me having proven them wrong...).
I spoke to a second garage (an MG specialist) who said testing emissions to determine whether the head gasket had gone was worthless and they never do it.
Are they both right???
What value does an emissions test have in determining whether a head gasket has gone? My garage missed the problem in my MG despite doing this test (and bizzarely still stand by this method, despite me having proven them wrong...).
I spoke to a second garage (an MG specialist) who said testing emissions to determine whether the head gasket had gone was worthless and they never do it.
Are they both right???
busman said:
Opinions please from those who know far more than I:
What value does an emissions test have in determining whether a head gasket has gone? My garage missed the problem in my MG despite doing this test (and bizzarely still stand by this method, despite me having proven them wrong...).
I spoke to a second garage (an MG specialist) who said testing emissions to determine whether the head gasket had gone was worthless and they never do it.
Are they both right???
What value does an emissions test have in determining whether a head gasket has gone? My garage missed the problem in my MG despite doing this test (and bizzarely still stand by this method, despite me having proven them wrong...).
I spoke to a second garage (an MG specialist) who said testing emissions to determine whether the head gasket had gone was worthless and they never do it.
Are they both right???
no - id rekon the second one is right and that the first one is really barking up the wrong tree. there are a myriad of other tests that will more accurately identify a blown hg and theyre not hard to do! A fair bit of water vapour would be the only thing i can think of that you can spot in the exhaust but this will vary anyway dependant on engine temp / ambient temp / fuel age / etc etc
surely a comp test with a gas probe in the coolant combined with an analysis of the oil and checks for sudden water / oil loss would be the way to go to check an HG?
GreenV8S said:
They're commonly called block testers. Maybe this is what your MG guys meant when they said emission tester? Although to me that mean exhaust gas emissions, and I don't see how you would detect a blown head gasket from exhaust emissions.
i dont know if it is that bad??????
really bad but the water spout of the filler cap would give it away first
block tester search for it on ebay
A compression test will let you know if a head gasket has failed. The device itself costs about £20 (halfords do them), and you simply test each cylinder, they should match the manufacturers values for pressure, and if there is, IIRC, a 10% (could be 15%?) variance in two adjacent cylinders (compared to the other cylinders), then the head gasket is most probably leaking.
To do the test, car must have been warmed up to normal temperature. Then switch off engine, disable the ignition(remove the leads or whatever, but make sure it is safe) and then:
remove a spark plug
plug in the compression tester
turn engine over for a set number of times (can't remember, but I think it was 10 times? The compression tester thing will probably have instructions), and keep an eye on how the pressure builds up (will be quick at first and then slow down)
record values
replace spark plug and go onto the next one.
This test can also help with finding other problems with the cylinders.
The mayo stuff on the dipstick or cap doesn't always mean head gasket failure, it could just be condensation.
To do the test, car must have been warmed up to normal temperature. Then switch off engine, disable the ignition(remove the leads or whatever, but make sure it is safe) and then:
remove a spark plug
plug in the compression tester
turn engine over for a set number of times (can't remember, but I think it was 10 times? The compression tester thing will probably have instructions), and keep an eye on how the pressure builds up (will be quick at first and then slow down)
record values
replace spark plug and go onto the next one.
This test can also help with finding other problems with the cylinders.
The mayo stuff on the dipstick or cap doesn't always mean head gasket failure, it could just be condensation.
ninja_eli said:
A compression test will let you know if a head gasket has failed.
There are so many faults that can affect the compression test results, and so many types of HGF that won't affect it, that I don't think a compression test is a very reliable way to detect HGF.
If you have exhaust gases in the coolant or oil in the water, it's almost certainly HGF or head/block failure (shifted liner etc). If you have water in the oil it may be HGF or it may just be condensation. HGF may cause low compression, or high compression, or not affect it at all.
The easiest way(and most common on the K)to check for HGF on this engine is to test for hydrocarbons in the cooling system,easily done by waving a gas analyser over the filler of the expansion bottle,if its failed it will detect hydrocarbons straight away(quick test)follow this up with the dye test (block tester)where the blue fluid changes to green/yellow(depending on brand) when combustion gases are detected in the coolant,the K can normally be found with an oil scum film in the expansion bottle,sometimes accompanied by a slight misfire on idle in extreme cases,if you run the car up to temperature then crack the coolant bottle top slighly enough to release the pressure(dont remove you may scald yourself)you can usually smell a exhaust smell from the pressure escaping(not good and a sure sign of failure),K series are generally not very good at covering up there HGF for long,any reputable garage can carry out these tests for you,good luck
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