Howdy folks,

Our 05 MCS, Scarlet, has an intermittent coolant leak. It leaves a little puddle under in the garage, various sizes of puddle depending on the day. Has done this on a very intermittent basis for a long time until recently, now getting more consistent. It's dripping off the front of the engine smack in the middle of the car where the water pump is, but not really while it's running. I installed a new Beck / Arnley water pump a while back, it has maybe 55k on it. I would have expected better from what I thought was a reputable brand, and I hate just replacing stuff when I don't know for sure if that's the problem.

Now it's on jack stands in service mode, as I have several things I need to do to it. I degreased it (also replacing oil pan gasket and crank pos o-ring, messy), so I washed away the evidence. I can still run the engine, so I'll let it get good and warm tomorrow in service mode and see if it gives me any visible evidence. I did notice today that the long upper rad hose has abraided significantly in one spot against the fan shroud. I'm amazed that bad boy didn't burst, it's not far off. That could be the leak, but I squeezed all over that spot and couldn't make it weep when cold.

Looking for advice, experience, something else to check while I'm looking. Or if it's just the water pump, and I gotta "suck it up buttercup", so be it. Thanks!

Jeremy

 

Maybe it's UV dye time. Could be the pump but could be a hose, connector, clamp, the bleeder, or the radiator itself. Or some combination.

 

UPDATE:

I have put the engine through two complete warmup - cooldown cycles, 30 - 40 minutes of idling, low speed fan was cycling normally. Remember it's on stands in service mode, so I can't drive it. No leaks, ARRGH. Using a flashlight and a mirror from above and below, I have found angles where I can see the bottom of the joint of the flange to the block by the lower bolt, the lower edge of that flange where the WP inserts with the big o-ring, the bottom edge of the WP itself where coolant should end up if coming from the weep hole (can't see the weep hole though), and the bottom of the rad hose that attaches to the WP. I can also see the radiator of course. The intermittent leaks have come right from the center of the car, and these are the cooling components in the center. Dry as a bone. That's frustrating, the intermittent thing.

I'm thinking it has to do with thermal expansion / contraction on thermal cycling. Even though the coolant temp was reaching 221C idling, everything I'm sure many components get hotter when driving for real. And thinking back (remember that there has been a very intermittent leak for a long time), the first time I noticed it was on a trip to Big Bear on a cold, near freezing morning in front of the cabin. Same location, little green puddle smack in the middle. I remember going "oh no, I just replaced this stuff", but then it didn't really get any worse. That was at least two years ago, and I've had to add coolant, just a bit, maybe once every two or three months. That makes me think it's most likely the big o-ring - insert fitting into the flange. I assembled that with silicone grease on the o-ring.

Help! Anybody had this combination of symptoms?

Thanks again, Jeremy

 

Middle towards front of engine compartment or middle at firewall?

 

Hi Euro, middle front, where the WP is on a 1st gen MCS.

 

Middle left then if near water pump...left side of SC.

Maybe bad connection there ?

That's almost same location of the Thermostat ( just above it ) .....a common leaker. I think I'm on my 3rd or 4th at 244K miles.

OEM gasket comes as kit with new Thermostat.

If it does needs replacing go OEM......

Seen some 1st Gen owners go "cheap" installing aftermarket thermostats not taking into consideration that the gasket which is the usual reason for being in there in the first place is an inferrior gasket. IMO the OEM one lasts longer.....

 

Ok, I'll take a look in there. I did the t-stat housing once before, and I'd have expected the leak to show up a little more to the left.

Anybody else experienced a very intermittent, thermal-cycling related leak as described?

 

Bump...anybody?

I'll be looking carefully at the T-stat housing area today. But again, that's more to the left, and my intermittent leak is smack in the middle-front where the WP is. Anybody have an intermittent coolant leak they fixed in the past?

Thx!

 

Welp, it finally showed itself. As mentioned, I ran it twice with full thermal cycles, no leak. Then it sat on the jack stands for a couple weeks while waiting for some other parts. Sometime in those last two weeks it decided to leak, so weird to me. It's that bloody o-ring seal where the pump inserts into the flange. I put that together carefully when I did the WP, grease on the o-rings, let everything center up before tightening the flange to the block. So what's up with that?

So, gotta get a couple o-rings (the one at the flange-to-block interface is the same PN).

Do people use the Mini OEM o-rings, are they anything special? Or just regular Buna o-rings? I don't remember them looking particularly special.

Jeremy