87 325is cooling sys help

[15Michaeljoseph]

So, I've had this bizarre condition for about 8 months, and I'm turning to r3v to help me. here's the info you get: It all started when my brand new upper rad hose blew for no reason, I was driving, but I didn't let the car get over 1/4 the way to hot. okay.... replaced the hose, bled the coolant. Then coolant starts to dissapear. bled it again. tank drains about half a tank per week and a half. took it to te mechanic (he installed this engine, my other one got toasted from a timing belt) Leakdown pressure tests found no leaks whatsoever in the system, but I've still been loosing coolant at a pretty steady pace. I took the advice of a post on a forum and hooked up a catch bottle to the overflow hose of my reservoir. For the first few weeks, little went into the bottle, but more recently, the thing's been full. filled almost to the brim with my fresh coolant. My guess is that there's too much pressure in the system, forcing it out of the expansion tank. I've already replaced the reservoir cap with new one, thinking this may solve the problem. It did not. I have the cylinder-looking coolant tank, mounted on the passenger side (i know there were like 3 different designs) so is it possible i bought the wrong cap? are they all the same? do I have too much pressure, and probably a busted head gasket? (thats what i read online), plus, yesterday I drove home, parked in the garage, and what's that? little droplets of oil on the driveway and in the street? lovely. backed it out... yessir, about 3x3in circle of oil on the floor, closer to the rear of the engine, but I doubt it's the rear main seal, that just got done.
the mechanic i've been using is INSISTANT that it isn't the headgasket. The car doesn't make smoke or anything, and the temp gauge is even below operating temp, always. so.... I'm really hoping I don't have a cracked head.
This problem has been giving ME a cracked head.

what do you think?


sent from 1987 via e30

[jlevie]

It sounds to me like a bad head gasket. The definitive test is to pressurize each cylinder with 170-180psi for several minutes while monitoring cooling system pressure with a sensitive gauge. A negative result on a cold engine requires that the test be repeated on a hot engine.

One DIY test is the catch tank in conjunction with a new expansion tank cap, which you have done with a positive result. Fluid in the catch bottle and the failure of the new hose indicates excessive cooling system pressure, which will be the result of a head gasket leak.

Another is to remove the cap when the engine is completely cold to release any pressure. The hoses will be soft. Drive the car, let the engine get completely cold, and see if the hoses are hard. Hard hoses then indicate that air is being pumped into the cooling system.

The last method is to fully bleed the cooling system, drive the car a bit, and re-bleed. Release of a significant amount of air during a re-bleed is evidence of a head gasket leak

[15Michaeljoseph]

I'm going to try those last two... thanks a lot man


sent from 1987 via e30

[blasphemy101]

Sounds very similar to a problem I had with a friend on his E34. A radiator hose blew up. Installed new hose, coolant bled fine and temp was solid. The new hose blew off later that night. I thought the system might be getting pressurized from a blown headgasket, but we spend the day trying to bleed the system fully.

The car went to two mechanics and got a new radiator before the shop concluded it was a blown headgasket. It may be the stereotypical case, but blown headgasktet != giant clouds of billowing white smoke.

[15Michaeljoseph]

but blown headgasktet != giant clouds of billowing white smoke.

well, I don't have a lot of smoke, lol, just the usual stuff you see in the winter.
oil's still coming out...front of the bell housing. oh jeez. calling the mechanic in a few to see what he thinks.



sent from 1987 via e30

[15Michaeljoseph]

my new conclusion: still too much pressure, but it can't be the HG, because it was replaced and the head was resurfaced. Also, I'm leaning toward a rear main seal for that oil.

so what else could cause the pressure?


sent from 1987 via e30

[dnguyen1963]

How can you be so sure about the HG? Where can the coolant system get air from? The air has to be pumped into the coolant system, i.e. the pistons via leaky HG. Just because you have had the head resurfaced and a new HG does not guarantee that your engine is having no leaks.

[jlevie]

+1

If the cooling system is over pressurizing, the head gasket is leaking or the head is cracked.

[blasphemy101]

well, I don't have a lot of smoke, lol, just the usual stuff you see in the winter.
oil's still coming out...front of the bell housing. oh jeez. calling the mechanic in a few to see what he thinks.



sent from 1987 via e30

Sorry if I wasn't clear. I was trying to say you can still have a blown headgasket, even if your car isn't making cumulonimbus clouds in your driveway.

A compression test might be helpful. My friend's M30 read slightly lower on two side-by-side cylinders.

How can you be so sure about the HG? Where can the coolant system get air from?

Also this - there are only so many ways large amounts of pressure can build up in your cooling system.