Coolant Leak

[SoCalDMC12]

While in traffic yesterday, I noticed my engine temp creeping up past normal. I stopped for a bit, filled the coolant bottle (which was almost empty) and was able to make it home. Later, I topped off the coolant, and took a 45 minute shakedown drive. The temp remained normal, and there was no coolant on my garage floor.

Today, I pressure tested the system, and (sadly) coolant began to leak from the lower-front-center of the engine. What I found odd was that visible signs of a leak only manifested when I did the pressure test. I would have expected to see coolant on my floor after my shakedown drive.

I'm taking her in to DMCCA next week to have the problem fixed. (Hoping it's not the water pump!!!)

[DMCMW Dave]

Coolant leaks can deceive you. When the engine is cold, there is very little pressure to force the coolant out (i.e. just gravity). Leaks can close up when the temp goes up so nothing is lost while driving.

A pressure test cold will show leaks that are not there when hot.

This often shows up as a cars that drip coolant overnight after a drive and then don't drip any more until next time.

[Citizen]

I discovered a coolant leak about six months ago. Found small traces on the garage floor, so I began capturing the coolant. I could never precisely trace the source, but it was coming from above or around the cat. I was hoping it was loose hose clamp or something easy. Had the car at DMC for some other work, and while there Stephen identified it as a bad freeze plug. I guess at 30+ years old, those plugs can deteriorate quite a bit.

Yes the leak was slow, but it was never going to get better, only worse. Has to be replaced. I was just glad it wasn't a gasket somewhere, or the water pump.

Maybe yours could be a freeze plug too?

[rundmc]

Don't feel bad, SoCal. I pressure tested my "leakless" cooling system cold after a fresh flush and refill and the system literally started leaking at EVERY junction point from bow to stern, creating a lake in the valley of death which has forced me to disassemble the intake manifold to clean, reassemble and test AGAIN.

[SoCalDMC12]

Coolant leaks can deceive you. When the engine is cold, there is very little pressure to force the coolant out (i.e. just gravity). Leaks can close up when the temp goes up so nothing is lost while driving.

A pressure test cold will show leaks that are not there when hot.

This often shows up as a cars that drip coolant overnight after a drive and then don't drip any more until next time.

I haven't seen any coolant on the floor in a long time, and I've been driving this car daily. I guess there's just a "sweet spot" during which the temp/pressure is just right for a leak to occur while driving, and yesterday the coolant level finally got low enough to cause the engine temp to rise. Fortunately I was really close to home.

Anyway, based on my 45 min. drive yesterday, I should be able to get to DMCCA on Monday to get the problem sorted.

[jawn101]

I haven't seen any coolant on the floor in a long time, and I've been driving this car daily. I guess there's just a "sweet spot" during which the temp/pressure is just right for a leak to occur while driving, and yesterday the coolant level finally got low enough to cause the engine temp to rise. Fortunately I was really close to home.

Anyway, based on my 45 min. drive yesterday, I should be able to get to DMCCA on Monday to get the problem sorted.

Did you run your heater at all during the drive immediately prior to detecting the leak? I ask because my system is tight as can be, with the exception of the heater control valve at the back of the engine. When I use the heater and engage that valve, I periodically see a few drips after the drive. I have a new one in the garage but haven't had a chance to install it yet. They are another one of those parts that is known to fail/rust out, and would be a cheap and relatively simple thing to replace.

[SoCalDMC12]

Did you run your heater at all during the drive immediately prior to detecting the leak? I ask because my system is tight as can be, with the exception of the heater control valve at the back of the engine. When I use the heater and engage that valve, I periodically see a few drips after the drive. I have a new one in the garage but haven't had a chance to install it yet. They are another one of those parts that is known to fail/rust out, and would be a cheap and relatively simple thing to replace.

No, I didn't use the heater (it's been really warm here this week). I did turn on the AC in order to get the fans working... but I don't think that did very much since the root of the problem was a lack of coolant.

[jawn101]

No, I didn't use the heater (it's been really warm here this week). I did turn on the AC in order to get the fans working... but I don't think that did very much since the root of the problem was a lack of coolant.

I was just reminded by another thread that the heater control valve is normally open except when Max A/C is selected. So this may still be involved with your leak.

[DMC5180]

I haven't seen any coolant on the floor in a long time, and I've been driving this car daily. I guess there's just a "sweet spot" during which the temp/pressure is just right for a leak to occur while driving, and yesterday the coolant level finally got low enough to cause the engine temp to rise. Fortunately I was really close to home.

Anyway, based on my 45 min. drive yesterday, I should be able to get to DMCCA on Monday to get the problem sorted.

You may be experiencing this: External seeping head gasket.

79817982

[SoCalDMC12]

You may be experiencing this: External seeping head gasket.

79817982

That looks... pricey.

[DMC5180]

It's not catastrophic yet, but will eventually require head gaskets and I may go Stage II heads at the same time. I've been told to try re-torquing the head bolts one at a time as a possible short term solution, but to expect doing head gaskets in the not to distant future.

[SoCalDMC12]

Well, it's the water pump. Major bummer, but I suppose it could have been worse... At least I didn't overheat and cause major damage to my engine.

[DMC5180]

Well, it's the water pump. Major bummer, but I suppose it could have been worse... At least I didn't overheat and cause major damage to my engine.

Did you verify the coolant was for sure coming from the weep hole behind the Pulley. If it isn't, then it's not the water pump itself, but rather leaking coupler hoses on the back side of it. (VOD)

[SoCalDMC12]

Did you verify the coolant was for sure coming from the weep hole behind the Pulley. If it isn't, then it's not the water pump itself, but rather leaking coupler hoses on the back side of it. (VOD)

Verified. :-(

[DMC5180]

Oh well, It's a good reason to go in and check your VOD and clean things out. Expect for at least one bolt to snap off in the process. (Murphy's law)

[dmc6960]

Mix yourself up some 50/50 ATF/Acetone for the intake, Y-Pipe, and water pump bolts.

[SoCalDMC12]

All fixed. So happy now. :-)