Head crack

30csl

30csl

Well-Known Member
Site Donor
Messages
1,345
Reaction score
15
Location
London/Herts
Hi guys,

since replacing the head gasket on my csl i have used the car quite a bit - it has gone well including the 1300 mile trip to Ireland.

Trouble is i have a feeling the head is cracked. Everyone i talk to says it cant be as it would be more obvious.

Why do i think it? When car is left idling up to temp - all is fine and the coolant stays in the syste, but if i take it for a drive and hammer it when i come home it seems to have lost quite a bit of water and evidence is some has come out of the overflow on the tank. Also when i take the header tank cap off there is a smell of exhaust gases.

I did compression readings for the sylinders and all were in line and good.

Short of pulling the head anyway to know for sure!?

I expected the coolant level to 'settle' but since then it has taken too much water for my comfort.

Thanks,

Rohan

p.s. - the head really is the mechanical achilles heel on these cars!
 
Hi Rohan,

doesn't sound, that the head is cracked. If the coolant remains (even just by relaxed driving) everything looks quite OK.

If the head is cracked the engine will "burn" water, which ends in enormous white steam coming from the exhaust. And it would also normally end up in an overheating of the coolant.

Also a good hint will be white grease/mudd sitting under the cap of the valve cover, which is a result of the existance of water inside the engine oil circle.

Your problem may probably come from the cap of the coolant reservoir. Could be, that it releases (over) pressure to early.

Also when i take the header tank cap off there is a smell of exhaust gases
Click to expand...

Would be more a sign, that the piston rings are leaking a bit imho.


Ingo
 
Hi Sfdon, I will try those next but have heard varying reports on their effectiveness.

Arnie, the cap sometimes has a slight milkiness but nothing much and not after a proper drive. Why would worn rings make coolant smell of exhaust gases?

Is it possible to have a crack where water is pressurised by the compression stroke but is not sucked into the engine? Otherwise one spark plug should look different right?

Thanks,

Rohan
 
Rohan,

Have you checked the condition of the oil? Does it look like coolant is getting mixed into it (milky/cloudy colour)?

When running with the coolant cap off, and warm, do you see bubbles in the reservoir? Potential source of the exhaust smell.

No obvious external coolant leaks?
 
Why would worn rings make coolant smell of exhaust gases?
Click to expand...

sry, was my mistake in reading your initial post. (Thought the smell was coming out of the valve cover, by opening it's cap.

The head of the original engine really can be a nightmare.
This was also a reason for me to do an upgrade to a later M30 engine. :roll:
 
30csl said:
Hi guys,

since replacing the head gasket on my csl i have used the car quite a bit - it has gone well including the 1300 mile trip to Ireland.

Trouble is i have a feeling the head is cracked. Everyone i talk to says it cant be as it would be more obvious.

Why do i think it? When car is left idling up to temp - all is fine and the coolant stays in the syste, but if i take it for a drive and hammer it when i come home it seems to have lost quite a bit of water and evidence is some has come out of the overflow on the tank. Also when i take the header tank cap off there is a smell of exhaust gases.

I did compression readings for the sylinders and all were in line and good.

Short of pulling the head anyway to know for sure!?

I expected the coolant level to 'settle' but since then it has taken too much water for my comfort.

Thanks,

Rohan

p.s. - the head really is the mechanical achilles heel on these cars!
Click to expand...

Hi Rohan,

I seem to recall similar discussions on this board - but never any specific resolution. I have neglected to search for similar threads and fear I may be repeating myself in this post. Sorry if this is the case.

If you have a hairline crack in either the head or the head gasket, (not saying that you do) the defect might be most apparent when the engine is cold. When the engine is warm, the metal expands and seals any fissures. Exhaust smell in the coolant is consistent with that theory since a cold engine’s coolant system is generally not under pressure. Combustion gases may somehow force their way into the coolant system and displace some of the liquid.

Of course, when things get hot and the engine is shut down, the pressurized coolant may seep between the fissure and into a combustion chamber. If things are hot enough the seeped coolant evaporates. At some point you might notice hard starting a cold engine and a misfire - that may clear up as you drive. If that happens, or if you suspect it is happening, you might pull the plugs - when the engine is still cold - and look for moisture. An exceptionally “steam cleaned” plug is another telltale sign.

Over the years I have experienced what you are describing but the symptoms became too pronounced to ignore - poor cold running and significant coolant loss. As mentioned, you could just have a leak somewhere in your cooling system. When you push things, pressure naturally rises. If the system cannot handle the pressure, you see external leaks. A whimpy radiator cap can have that affect. As you know, radiator caps are pressure rated and maybe yours has gotten tired or has a compromised gasket. Radiators, overflow/expansion tanks don't last forever, could yours have a barely there leak? (I just had a 1 year old plastic tank crack at the filler neck.) A lazy thermostat can also raise the pressure, but it usually goes hand in hand with overheating. Lastly, as you pointed out, cooling systems generally find their own coolant levels and will not tolerate being overfilled. Could you be inadvertently overfilling yours?

Hth

p1030132.jpg



DSCN27823.jpg
img4677w.jpg

 
Well guys, thanks for all the help. MM - it is not too different when warm or cold. The oil looks fine, no visible coolant leaks, no bubbles when idling with cap off and it only seems to throw it out of the header tank when driven hard. I think suggestionx for a new radiator cap are a good next step. If the header tank didn't smell of exhaust I wouldn't be too concerned. Damn weak heads!
 
30csl said:
Well guys, thanks for all the help. MM - it is not too different when warm or cold. The oil looks fine, no visible coolant leaks, no bubbles when idling with cap off and it only seems to throw it out of the header tank when driven hard. I think suggestionx for a new radiator cap are a good next step. If the header tank didn't smell of exhaust I wouldn't be too concerned. Damn weak heads!
Click to expand...

Are you sure about that smell. Because when the car is not running even the exhaust does not smell of exhaust. Maybe try Febreeze?
 
30csl said:
not too different when warm or cold. The oil looks fine, no visible coolant leaks, no bubbles when idling with cap off and it only seems to throw it out of the header tank when driven hard. Damn weak heads!
Click to expand...

R:

You never state exactly how much coolant you are loosing per day or mile - which leads me to wonder if you couldn't continue driving for a very long time as-is. I would bet that most folk who have a head or head gasket problem only discover it after the temperature gauge reads 2:00 o'clock or when onlookers ask if the car is steam powered. By the time this happens, it's a little late to start thinking about that last 1990 coolant flush. Also, you did not explain whether you are topping up the system with Guinness or Watney's Red Barrel.

Anecdotally, I have seen cars driven for years while being nursed along with frequent radiator top ups. But this can also be due to minor radiator leaks, loose hoses and weeping water pumps that some can overlook. Not advocating this, unless you work for an Autoclub or you have a trusty factory sponsored support team.

To be sure, the later head design with more metal around the water jackets is superior to the older version. However, (gulp) there are many of the earlier heads still in service and used on a regular basis. If given the choice, I would elect the newer version, but that doesn't mean I would automatically exclude using the older-style if it were still in decent shape. The thinner water jackets may be more prone to deterioration and failure, but much of that may be due to neglect of the coolant system. I base this on having seen a few failed M10, M30 and other aluminum heads that were extremely corroded. Such corrosion generally occurs over a long time, with routine maintenance - much quicker without it. For that reason, I would be more inclined to blame a head gasket before condemning the head, even if it is an early version.

P1010188.jpg


0ead6c05.jpg

12f14f74.jpg
 
....Or you could pressure test it to be sure - kits are readily available to determine hot or cold internal or external leaks
 
I had a hairline crack in the head on my Austin Healey Sprite race car that was very difficult to find. It would run perfectly fine but after about 15 minutes on the track, it would start over heating. The hairline crack was small enough that very little coolant would get into the combustion chamber but compressed gasses could get through it into the coolant. This caused the coolant to foam up and increase the pressure in the cooling system. This foam would then slowly get pushed out of the radiator cap into the catch tank. I eventually found the hairline crack and had to scrap the head.

I suspect you may have a similar problem but it could also be a head gasket causing it.
 
MM mentioned something very briefly that I think you should check: the possibility of a leaking water pump.

Warm the engine up, then get your head under the front center of the engine and look up with a good light. There is an approximately 1/8" (3 mm) hole in the "neck" of the water pump casting that runs forward to the fan pulley. If there is a drop of water there, the water pump seal is leaking. I suppose it will leak more after a good warmup when coolant system pressure is up to 1 bar.

Eventually the bearing will corrode and the fan will become wobbly, possible (eventually, again) to the point where it can hit the radiator core. You will hear the wobbly-ness before the core is endangered, usually on startup or shutdown.

A slightly leaking pump gives you some time to consider how soon you want to replace the pump, as long as you are diligent about adding coolant.

Although plain water is the best heat transfer fluid, if you only run water in your cooling system it may corrode things much faster. This we don't want; use a little approved coolant in the concentration appropriate to your climate and needs.
 
Hi Rohan,

I think the pressure testing idea wins as your next step IMO, however just to add - I know the previous owner of my car (69 2800 CS) had this problem - He solved it by getting hold of what he called a "Spanish copy head" - Which has thicker metal between cylinders as mentioned previously here.
 
Ok guys,

I will take the advice and go buy a coolant system tester - given i am unlikely ever not to own an M30 engined BMW it is a good investment!

I did check for leaks and the water pump and all other likely leak sources are dry - i also had it running in the garage with cardboard under it and that was bone dry. I only meddled with the head to fix an oil leak which has stopped but it may mean i have cracked the head in the process of changing the gasket - same old story - one step forward two back.
 
Did you clean the head bolt bores when you changed the head gasket?
 
You must log in or register to reply here.
Back
Top