1999corvettels1

I have had a mystery leak on the coolant overflow tank for maybe 3 years, very small leak that looked like it was coming from under the cap, and then running somehow down to the seam of the tank, and having the coolant there.

I have wiped it off and driven it, and not seen it for a long time, but after time, I would see the coolant at the seam.

Today I took the car for a drive first time in 2 months, and after getting back I hooked up the charger to charge the battery a little more, I saw bubbling where the steam line connects.

Wiped it with a rag and saw a hairline crack on the tube the line hooks to, so, that must have been where it was leaking all along.

I tried to wiggle it and it moved and the crack expands.

Is this a common failure area on these tanks?

1999corvettels1

I'm going to guess when it would leak before, it only did it when the car was sitting, because I would look at the tank after a drive to see, and it would be clean.

Sitting is bad for cars lol

maxx2200

Mine had an intermittent leak (hot) around the bottom of the nipple. It would leak in an area that I coudn't see. Finally located it and replaced the tank and cap. Easy job and not expensive.
I agree that sitting for extended periods of time takes it's toll on certain items. All the more reason to drive!

1999corvettels1

Oh, I would not attempt to fix it, just replace it. My car has about 82K on it, probably just time that made the plastic break.

LoneStarFRC

Yes. Heat aging plus over time it can get damaged from leaning on it or putting weight on it while working on the car, especially when covered with a fender cover. I fabbed a small piece of rubber (from fuel line hose) and slid/wedged it underneath that nipple to keep it from flexing downward if weight is put on it. Kind of a "half circle" shape.

For new tank:

amazondotcom

ACDelco 10405218 Radiator Surge Tank $57.65 w/free shipping

DARRYLZO6

Like they said. If its original its likely leaking from the stem or the seam. Rock Auto seems to be the cheapest about $50. Also the newer versions seem to be clearer plastic. Ask me how I know.

1999corvettels1

Not too bad, I would have never thought of Amazon for car parts.

Hmm, I don't remember ever leaning on it before, but it's possible.

LoneStarFRC

It's an easy thing to do especially when you don't realize you're doing it. Usually most guys cover their fender with a fender cover or blanket or some such, and are not aware.

Although I like Rock, I've also had Amazon on my "favorite source" list for several years and have found some items cheaper, especially when there's no charge for shipping. They can be very competitive on many things.

DARRYLZO6

jgump

Mine leaked there as well at 75K. Replaced the tank with new. Looks Purdy.

Vetteman Jack

I have heard of them cracking in that location before. New tank and you're set to go.

racebum

all the coolant hoses and the radiator should be changed at ten years on a c5 imo. every coolant hose on there is at risk of this happening and a single tow can be as expensive as replacing all of this stuff. the plastic also gets brittle on the radiator but that's not usually the worst issue. the worst part is heat transfer is reduced via debris and scaling over the years. this means the car starts running hotter increasing your chance of detonation among other things

EddyVeter

I just received my new tank from Amazon. Thanks for the info. One question though. I didn't look yet but I'm pretty sure the one in my car does not have a temperature sensor on the bottom. If so I guess I just ignore the connection then?

EddyVeter

OK, so I just saw on another thread that 2000+ vehicles do not have the connector to tank. Can I still use the tank I purchased even though it has a connector on it. I assume it shouldn't matter but you never know.

Thanks for you help.

LoneStarFRC

I can't think of any reason why not. If there's nothing to plug in, just disregard.

Btw, before the end of the C5 run, GM changed the spec on the cap from 15lb to 18lb so if you go to replace, don't bother looking for a 15. Just a FYI.

EddyVeter

Thanks LoneStar for your info and cap data too. I'll hopefully get to this tomorrow. This forum has been very helpful and appreciate the depth of knowledge and info here.

onspeed

Had same issue as you back in June. Changed the tank with one on clearance at Rockauto for $30. All is well now, coolant level doesn't change at all.