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-   -   Expansion Tank Cracking (http://www.clubcobra.com/forums/era-speak-bob-putnam/146080-expansion-tank-cracking.html)

RockBit 07-09-2022 09:21 AM
Expansion Tank Cracking
 
1 Attachment(s)
I have had my expansion/surge tank crack twice, and have had it repaired at a radiator shop both times. I can't remember the particulars about the first time (cracked in solder joint between tank bottom and tube to thermostat), but the second time it cracked was after a hard acceleration. It cracked in the corner of the tank top on the passenger side.

After searching, the most likely explanation is that the upper radiator hose is too stiff, and stresses the surge tank when the engine rocks over from torque.

Short of buying a new, stronger surge tank, does anyone have a suggestion for how to fix this?

g4g2g7 07-09-2022 09:57 AM
1 Attachment(s)
Might just be the angle of the photo, but looking at something simple first that might tie into your comment about stress under torque, kinda looks like the upper hard elbow doesn’t line up with the radiator inlet preloading the setup?

Morris 07-09-2022 09:59 AM
Yes......go to a SS tank and change the hoses to silicone rubber hoses.....

Check out Pegasus Racing or HRP Racing....

bobcowan 07-10-2022 09:30 AM
If the engine is moving enough to damage the tank, it's putting stress on other areas as well. You've only discovered the weakest link. When you fix that, you'll find the next one.

I would install solid motor mounts. Cheaper. Easier. Fixes everything

RockBit 07-11-2022 06:37 AM
Quote:
Originally Posted by g4g2g7 (Post 1508392)
Might just be the angle of the photo, but looking at something simple first that might tie into your comment about stress under torque, kinda looks like the upper hard elbow doesn’t line up with the radiator inlet preloading the setup?
I think what you are seeing is just from the angle of the photo. The hose connecting the upper radiator outlet to the tube has a radius in it and is short.

RockBit 07-11-2022 06:38 AM
Quote:
Originally Posted by Morris (Post 1508393)
Yes......go to a SS tank and change the hoses to silicone rubber hoses.....

Check out Pegasus Racing or HRP Racing....
Thanks for the suggestion. I am hoping to fix this without having to purchase a new surge tank. They seem to be in short supply, as well.

RockBit 07-11-2022 06:41 AM
Quote:
Originally Posted by bobcowan (Post 1508424)
If the engine is moving enough to damage the tank, it's putting stress on other areas as well. You've only discovered the weakest link. When you fix that, you'll find the next one.

I would install solid motor mounts. Cheaper. Easier. Fixes everything
I have an aluminum block. With solid motor mounts, would the be a danger of stripping the motor mount threads in the block? My engine dynoed at 660 lb-ft…

strictlypersonl 07-11-2022 07:29 AM
This might help.
https://erareplicas.com/427man/engin...tmod/index.htm

RockBit 07-11-2022 08:40 AM
Quote:
Originally Posted by strictlypersonl (Post 1508450)
Thanks Bob, but I already have the bolt through the motor mount.

bobcowan 07-11-2022 09:59 AM
Quote:
Originally Posted by RockBit (Post 1508449)
I have an aluminum block. With solid motor mounts, would the be a danger of stripping the motor mount threads in the block? My engine dynoed at 660 lb-ft…
Not a problem. I also have an alum block, and am making similar power.

Chicagowil 07-12-2022 12:19 PM
Quote:
Originally Posted by RockBit (Post 1508449)
I have an aluminum block. With solid motor mounts, would the be a danger of stripping the motor mount threads in the block? My engine dynoed at 660 lb-ft…
And solid motor mounts on race (1/4 mi) cars are prone to causing cracks in the side of the block around the mount bolts.

I would suggest replacing the alum elbow and rubber couplers with a pre-formed rubber hose. It would allow for more twist and flex as the motor moves around.

RockBit 07-12-2022 01:43 PM
Quote:
Originally Posted by Chicagowil (Post 1508500)
And solid motor mounts on race (1/4 mi) cars are prone to causing cracks in the side of the block around the mount bolts.

I would suggest replacing the alum elbow and rubber couplers with a pre-formed rubber hose. It would allow for more twist and flex as the motor moves around.
Great suggestion and something I am thinking about. First, though, I am going to rig something up to help me measure the movement of the engine to make sure of the cause. Stay tuned and I’ll post the results.

RockBit 07-16-2022 09:12 AM
I measured the engine movement during a spirited drive and got 1/4 inch. That makes sense as I have a bolt through the engine mount on the driver side.

It does not, however, explain the surge tank cracking. I’m stumped now, and I guess I won’t worry about it until it happens again.

Thanks to everyone for their comments and suggestions.

sunman 07-16-2022 11:49 AM
Maybe the weight of your elbow flopping around and the lack of flexibility is causing the metal fatigue problem.
Make a one piece rubber elbow fit and replace the four ugly hose clamps with two Earls AN style hose fittings to match those other two.

strictlypersonl 07-16-2022 02:26 PM
How about something like this?
https://www.gates.com/us/en/fluid-po...00-000000.html


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