Mtf1980

Overflow tank issues

59 posts in this topic

The metal insert inside the nipple where it fails has been removed in the revised tank . Time will tell if it holds up better than the original design 

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4 hours ago, sparkfanatic said:

The metal insert inside the nipple where it fails has been removed in the revised tank . Time will tell if it holds up better than the original design 

Let us hope the new design is a genuine improvement.

I never had to design any plastic components during my 23 years working for an outfit which designed and manufactured machines subjected the most brutal loads in machinery world. So I know nothing about designing parts made from plastic. But physics is physics no matter what material is used. Our machine structure was put together by welding together mild steel plates upto 12" thick. One category of machines we designed and built were cold extrusion presses. You start with a cold rolled steel bar and whack it between 2 dies made of tool steel with such force that the cold metal becomes plastic and flows to take shape of the dies. The impact forces generated on the welded steel structure of the press are unbelievable. 

 

Now that you understand where I am coming from, one thing I always avoided was to avoid any critical welded joint to bending stress. Bending stress during each cycle cause alternating tensile and compression stresses and that is a short cut to fatigue failure. I always strived to design any welded joint with shear stresses
(instead of tensile stress). Looking at the coolant overflow tank the return hose is attached to the horizontal nipple of the plastic tank. Which means every bump the car hits will cause bending stress on the plastic nipple extension from tank. The designer had 2 options..either beef up the plastic enough to lower bending stress below fatigue stress level..or design the return hose coming in from the top which will minimize bending stresses in the plastic.

 

Just my 2 cents worth. Incidentally our largest customer for our machines was General Motors, who used them in mass production of metal components for the their automobiles.  

Edited by Bobby MSME

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17 hours ago, Bobby MSME said:

[Snipped]...Bending stress during each cycle cause alternating tensile and compression stresses and that is a short cut to fatigue failure. I always strived to design any welded joint with shear stresses (instead of tensile stress). Looking at the coolant overflow tank the return hose is attached to the horizontal nipple of the plastic tank. Which means every bump the car hits will cause bending stress on the plastic nipple extension from tank. The designer had 2 options..either beef up the plastic enough to lower bending stress below fatigue stress level..or design the return hose coming in from the top which will minimize bending stresses in the plastic.

Excellent analogy Bobby...I covered this exact stress factor due to bumping/vibration in a previous post. This would not be an issue if the tank and material were designed with that in mind. Having a metal tube insert in the coolant return area causes more expansion differential than a tank with common material. It is my understanding that the new tank design now available for the Spark, Sonic and Cruze do NOT have the metal insert in the coolant return location..common material but not sure if the plastic is a different grade to withstand the hot/cold cycle that will deteriorate the flex of the plastic material...Still, it has obviously been noted and perhaps corrected by supplier to the tanks to GM. I still believe that although no recall is needed, failure should be covered under some kind of notice to dealers.

Ben&Jerry's likes this

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There's a expansion and contraction issue with that metal insert eventually weakening and then  splitting the plastic nipple along with probably the stress helping it along . Fortunately the tank is cheap and easy to replace . I bought all new hoses that I haven't gotten around to install yet .

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 I purchased my 2014 Spark new and after a few months I had problems with it overheating and they ended up having to replace the over fill for the antifreeze so apparently it's a bug in the car but after they replaced it everything seems fine with that part of it anyway.

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Edited by Dawn G
Misspelled

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Just sent my Spark away on a flatbed to be worked on at the dealer tomorrow. I noticed a lack of heat about a week ago and thought it was a thermostat issue. Kept driving it and then had the impetus to check the coolant level thanks to this forum and didn’t see any in the expansion tank :/ 

 

Bought coolant right after noticing the dangerously low level and filled the tank until it was a puddle in the tank because the engine was still hot. Filled it up the rest of the way this morning when the engine was cold. After driving for 15 mins I saw stem coming from the hood and the smell of dexos wafted in the cabin. Pulled over and let the car cool and saw bubbling out of the expansion tank nipple closest to the firewall on the top of the tank (I assume this is the dreaded return nipple). Let it cool some more for 90 mins and then drove it home about 20 minutes. I checked again and saw fresh dexos splattered over the left side of the engine bay. I decided that I couldn’t drive my car to the dealer near my house (about 25 miles away) so I dropped my car off at the dealer for a service appointment tomorrow. 

 

Reading this thread has has given me a much greater understanding of this issue and I can go into the dealer much more confidently. I’m still wondering what’s causing the coolant surge and if it’s related to the head gasket at all. I’m also getting the water pump inspected since I drove it around on low coolant (no light ever came on but still).

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  ..

Edited by Mr.tozzi

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My spark finally got the overflow tank issue. I think it’s leaking from the seam. Going to get a new one and do the swap, only have 28,000 on her now. 

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Picked up a new tank with revised part at my local dealer. Going to swap tomarrow. 

 

 

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