Do I have a Head problem or a shagged expansion tank cap?

following on from yesterday , I have carried out a COMP test on all cylinders and they're as follows:

Cylinder - Psi

2 - 130

4 - 125

6 - 130

8 - 115

1 - 120

3 - 125

5 - 130

7 - 125


in the actual compression test I cranked the engine 5 times each time a measurement was taken with throttle on maximum on every test. now wheather I've done it correctly, i donno.:(
what is the ideal test result supposed to be ? are they excessively low , I know cylinder 8 is measuring rather low 115. Is all not revealed yet ?? will I still need to do a lead-down test as well ?

are they the wet or dry numbers...

what youve done is near enough to correct but just for argument the correct method (well the way I do it) for doing the comp test is...

• disable the fuel pump, (you should also dump the fuel out of the rail/carby I normally do this by starting the car then pulling the fuel pump relay or unhooking the suction line to the tank while the engine is running)
• remove all the plugs and leads
• fit a test plug to the coil or refit leads and plugs to the coil packs then earth the plugs so they will spark normally, This stops any potential damage to the electrics.
• fit the compression gauge to the desired pot and crank it over till it reaches max pressure (should only take 4-5 revolutions)
• repeat as required on all cylinders.

This is your dry test.

put about a teaspoon of oil down each pot and wind the engine over by hand 2-3 revolutions to spread the oil and then repeat the test on all cylinders.

this is your wet test.

your pressures should all read higher on the wet test than the dry test. If you have a low pot (#8 in your case on your last test) that comes up good with a little oil then you have the start of bad ring/bore tolerance, If it stays low (relative to the other pots) or doesnt change then you have either a dodgy valve/gasket or something else bad and its time for a leakdown test.

at this point given that all your other pots are fairly close a proper leak down tester shouldnt be required just get an old plug, hack it up and fit a QD for an airline to it (weld) so that you can put air into the pot at about 100psi. fit it up and add the pressure then listen for where the air is going to.

Dave , those readings above are from a "Dry test" , from what you've described , engine was cranked 5 times on full throttle :)on each test as said , the car had also been driven on gas prior to switching it off, it seems from your post that I also need to do a "wet test" as well.

also I took expasnion tank off completely and gave it a good fluch and clean , put it back then flushed the cooling system again with tap water a few times to try and flush out some of the Chemweld , some came out , I dare say ther is a heap still inside , but I have also noticed very tiny silver specs which appears to be metals shaving in cooling system ???:( is that normal ?? i shall think not ? and also very mynute amounts of oil. probably too early to panic Yet...:(

Running a hose through your rad isn't flushing it.I paid $110 today to get my defender done,pay the money,they pressure test as part of the service and refill with coolant.The pressure test will show up a problem. Pat

If its actually oil and not just residue you might as well stop now and pull the heads. the metal shavings might be bits off of the impeller or they might be bits left over from a poorly cleaned up machining job.

I'll be bringing my flushing gun with me (sis put the wrong coolant in her crumpledoor) but I wont have a pressure tester if you've got a decent air compressor I can line up letting you use the flush gun for a few hours as needed. Once youve gotten the comp tests sorted and the leak down checked and your happy with it take it down to your local radiator place and ask them to give the cooling system the full 9 yards.

Quote:

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Originally Posted by PAT303

Running a hose through your rad isn't flushing it.I paid $110 today to get my defender done,pay the money,they pressure test as part of the service and refill with coolant.The pressure test will show up a problem. Pat

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actually Pat , that's not quite the way I did it , I drained all the old coolant out by undoing the bottom radiator hose , I then placed it back in, filled the radiator with water ,switched the car on, let the engine run idle for about 15-20 minute each time and got it hot I then switched it off undid the bottom radiator hose again and drained all the hot water out and replaced the bottom hose ,I repeated this process 5 times , that's how I was seeing metal shaving & chemi-weld appearing at the top radiator plug, if it were coming out from bowls of the engine.

TBH - It's not uncommon for the head gasket around Cyl 1, 2, 7 or 8 to fail and for the gases to end up in the cooling system (due to the proximity of the water channels to the edge of the cylinder).

BTW - When it last happened to me, the pressure build up blew out my radiator. :o

M

Heres another easy way to test for a head leak,
Do this test cold, first thing in the morning .
Fill the expansion tank up till overflowing. disconnect coil lead and crank engine. If the level goes up and starts to spill over the top of the expansion bottle then it is being pumped out by compression gasses. I would agree also with Camel Landy, I think number 8 cyl is possibly where the leak is, as all the end cylinders are very close to the water jacket...

JC

Quote:

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Originally Posted by justinc

Heres another easy way to test for a head leak,
Do this test cold, first thing in the morning .
Fill the expansion tank up till overflowing. disconnect coil lead and crank engine. If the level goes up and starts to spill over the top of the expansion bottle then it is being pumped out by compression gasses. I would agree also with Camel Landy, I think number 8 cyl is possibly where the leak is, as all the end cylinders are very close to the water jacket...

JC

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Thanks Justin , Just out of curiousity , would it matter if this test was done whilst car was parked on a steep drive way , or will it need to be parked flat?

justinc, OOC, how well does that work on a head/gasket thats just letting go?