How to Confirm HG Leak?

[e30rik]

So my 325is is eating coolant like crazy. I pressure tested the cooling system and couldn’t find any leaks so I’m obviously suspecting the head gasket now. I do get some steam out of the exhaust but goes away when the engine is at operating temp. The car does not overheat ever and the oil and coolant don’t seem to be mixing visually. I even bought one of those exhaust gas testers for the expansion tank, it passed the test.

I guess I don’t mind doing the hg job but is there any way I can confirm that’s the issue before I go that deep?

[88Sedan]

Make sure it's not a pinhole leak somewhere. I think they make UV dye for coolant like they do for oil. That and protective glasses at a dark time can help you locate any leaks. There are no signs of dry coolant anywhere?

[reelizmpro]

Sounds like you have already performed a block test but are you sure you did it correctly? When I first did it, I barely noticed a change in the color from blue to blue/green (not yellow) so I didn't think it was a HG. Turns out it was a bad HG. I suppose I didn't run the test long enough for the fluid to turn yellow. Green = Blue/Yellow. So any change to green/yellow should indicate presence of exhaust gas in the cooling system.

[e30rik]

Make sure it's not a pinhole leak somewhere. I think they make UV dye for coolant like they do for oil. That and protective glasses at a dark time can help you locate any leaks. There are no signs of dry coolant anywhere?

No signs of dried coolant and I feel like with the amount I'm losing an external leak would have been pretty evident with a pressure test but I like the dye idea.

Sounds like you have already performed a block test but are you sure you did it correctly? When I first did it, I barely noticed a change in the color from blue to blue/green (not yellow) so I didn't think it was a HG. Turns out it was a bad HG. I suppose I didn't run the test long enough for the fluid to turn yellow. Green = Blue/Yellow. So any change to green/yellow should indicate presence of exhaust gas in the cooling system.

Good point, when I performed the test I was definitely looking for a clear change. I may have missed a slight blue to green. I guess I'll try the test one more time and watch closely.

[bangn]

Check the overflow hose hasn't been pushing out coolant (tip of the hose will be wet and should be dry),

is your temp gauge displaying hotter - ie at the first line after center?

does the engine cough and splutter at startup and then clear up?

are any of the plugs coloured/black differently than the rest?

have you inspected the bottom of each radiator tank as the ends can leak slowly when faulty?

do you smell any coolant or get a horrid haze on the windscreen when you put on the heater?

[TobyB]

Taste the moisture coming out of the tailpipe- that'll tell you in a hot second if it's coolant.

2 things to try- relieve the pressure in the cooling system, then
start it cold, rev it once or twice to 3500, then switch off. Then see if
a; the rad hoses are pressurized or
2; there is coolant in any of the bores.

hth
t

[88Sedan]

Depending on general engine condition as well, you may remove the spark plugs and with a light look into the cylinders/top of pistons and if one or two are much cleaner than the rest than that's probably where the coolant is going.

[e30rik]

Check the overflow hose hasn't been pushing out coolant (tip of the hose will be wet and should be dry),

is your temp gauge displaying hotter - ie at the first line after center?

does the engine cough and splutter at startup and then clear up?

are any of the plugs coloured/black differently than the rest?

have you inspected the bottom of each radiator tank as the ends can leak slowly when faulty?

do you smell any coolant or get a horrid haze on the windscreen when you put on the heater?

I put the overflow in a bottle and got nothing.

Temp never goes higher than middle.

The engine is running a bit weird but I guess I should mention It's been sitting for a couple months, finally have some time to work on it now.

Plugs all look roughly the same.

I checked the whole system for external leaks and don't smell any coolant inside the car.

Taste the moisture coming out of the tailpipe- that'll tell you in a hot second if it's coolant.

2 things to try- relieve the pressure in the cooling system, then
start it cold, rev it once or twice to 3500, then switch off. Then see if
a; the rad hoses are pressurized or
2; there is coolant in any of the bores.

hth
t

I didn't get any moisture from the exhaust today but it is like 90 degrees here now. I tried what you said, the hoses didn't seem to pressurize, I pulled the plugs, didn't really see anything.

I also ran the block test again, let it run for a few minutes and watched the fluid closely, it stayed blue.

So, when I was last driving the car (a couple months ago) I didn't see any indication of water in the oil but today was the first time I've touched it since and there did seem to be a little cream on the dipstick but then I pull it 5 seconds later and it just looks like regular oil at the proper level. I think condensation is unlikely with the ambient temp out here. I guess I'll drain the oil tomorrow and see.

[TobyB]

I don't mean to get your hopes up too much, but you don't have the usual headgasket symptoms.

Sure the heater core's ok?

t

[e30rik]

I don't mean to get your hopes up too much, but you don't have the usual headgasket symptoms.

Sure the heater core's ok?

t

Preparing for the worst but I did drain the oil and it was just oil so we're good there. I ordered the UV dye that was mentioned and I'll see if I can detect a leak that way. As for the heater core, I can't really be sure of anything but I don't smell coolant in the interior, no moisture on the floor and no haze on the windshield.

[e30rik]

Alright, another update... I added the dye to the expansion tank and I still can't find any external leaks. I even rented the pressure tester again and this time I took the spark plugs out while testing. It pretty much held pressure for about an hour and a half, maybe half a psi loss, if that. Plug holes are dry, I even pulled the fuel pump fuse and spun the engine, no coolant came out. Pressure test would show a leak in the heater core, correct? If so, it has to be the expansion tank cap, tho I did check that with the black light. As I said before the car has been sitting and the weather was colder when I was driving it but I definitely had to add close to a gallon of coolant during that time so it went somewhere... I guess replace the cap and send it?

[TobyB]

That's what I'd do, after making DAMNED sure the level light on the reservoir worked!

t
that light has saved at least 3 engines for me- so far.

[e30davie]

I have a dumb suggestion. is it automatic? its not inside your automatic gearbox by any chance?

or the classic, its in your sump? I filled a sump with water once.

A gallon (4 litres?) is a heck of a lot of water. although if you've pressurized the cooling system then my 2 ideas don't make any sense.

[e30rik]

Bad news, UV dye gave me the answer, just not the one I hoped for lol. There’s a very tiny amount of bright green under the oil cap. Still makes no sense because of the amount of water I lost originally would have surely been evident when I drained the oil? She still runs pretty good so hopefully I didn’t damage the engine too much.