Coolant loss - head gasket? BMC 1.5

[SimonA]

For a while now every time I check the water level in the Bowman heat exchanger I have found it empty. The engine never overheats. Today I run it up to temperature and went out with the engine covers off, I noticed that above 2000rpm the coolant was running out of the overflow below the pressure cap. At lower revs all was fine. I then stopped the engine, took off the pressure cap and run the engine, almost immediately the coolant came shooting out of the filler. I didn't notice a lot of bubbles which was what I was looking for.

Next I took off the oil cap to check for mayonnaise which is usually a sign of a blown headgasket. There wasn't any. I checked the dipstick and the oil looked runny but with no sign of any white or milky stuff.

Does this sound like it could be the head gasket? I had the entire engine rebuilt about 3 years ago at great expense and it hasn't really run a lot of hours since.

The engine runs fine and starts straight away. The only thing I have discovered is a small wet patch of what appears to be diesel under number 1 injector. The fuel pipes are all tight so it hasn't come from them. Once again a possible sign of a head gasket?

How difficult is it to change the head gasket on a BMC?

 

[vas]

shouldn't you start with a new pressure cap? (much cheaper than a cyl/head removal or whatever. Don't know this engine at all, but many engines run a pressurised system that iirc enables coolant to run at a higher temp without boiling...
A leaky/loose spring or whatever on the pressure cap would produce such symptoms.

all imho of course

V.

 

[Jurgen]

Just had a Head Gasket go on my 4.2DL Mercruiser

Most obvious sign is oil in the coolant.

Check your oil filler cap for signs of emulsified oil.

Again dont know your engine so hopefully Mercuryman or Volvopaul will read the thread and offer advice/opinion.

Best of luck

 

[volvopaul]

For a while now every time I check the water level in the Bowman heat exchanger I have found it empty. The engine never overheats. Today I run it up to temperature and went out with the engine covers off, I noticed that above 2000rpm the coolant was running out of the overflow below the pressure cap. At lower revs all was fine. I then stopped the engine, took off the pressure cap and run the engine, almost immediately the coolant came shooting out of the filler. I didn't notice a lot of bubbles which was what I was looking for.

Next I took off the oil cap to check for mayonnaise which is usually a sign of a blown headgasket. There wasn't any. I checked the dipstick and the oil looked runny but with no sign of any white or milky stuff.

Does this sound like it could be the head gasket? I had the entire engine rebuilt about 3 years ago at great expense and it hasn't really run a lot of hours since.

The engine runs fine and starts straight away. The only thing I have discovered is a small wet patch of what appears to be diesel under number 1 injector. The fuel pipes are all tight so it hasn't come from them. Once again a possible sign of a head gasket?

How difficult is it to change the head gasket on a BMC?

These engines always spill out coolant as there just isn't enough volume in the heat exchanger , most people fill itbtomthe top to find it pushed out after a run. To test for head gasket you can buy fluid to test for compression gasses in the coolant.
I often test for a quick resot by fitting a rubber latex glove over the cap aperture, clamp it with your hand and run the engine, if it expands very quickly then there is a big chance compression gasses are doing this which means head off and new gasket, I would also check for distortion at a machine shop.

 

[SimonA]

I often test for a quick resot by fitting a rubber latex glove over the cap aperture, clamp it with your hand and run the engine, if it expands very quickly then there is a big chance compression gasses are doing this which means head off and new gasket, I would also check for distortion at a machine shop.

Thank you, I will try that.

 

[Nostrodamus]

I had an almost identical problem with my volvo..I would often find that the coolant level had dropped after using the engine for a while as it had run through the overflow pipe and into the engine bilge. I found it was my own fault for putting too much in. I needed to fill it to about an inch below the cap. When I did this it ran a bit cooler for some reason and there was no loss of fluid.
I don't have a expansion tank which most boats seem too and wondered if adding one would make any difference?

 

[PCUK]

I fitted a reservoir to my 1.5 as it always did the same thing.

 

[Nostrodamus]

I fitted a reservoir to my 1.5 as it always did the same thing.

Thanks PCUK.. saved me time and money