[mrennie]

Hello,

Last year, I noticed a small coolant leak somewhere near the DS bottom corner of my Griffin aluminum rad. This rad was from a group buy we did here probably 10-12 years ago. My car is not yet fully assembled and has not seen the road, but the rad was used with my engine test stand back in 2014 and had no leaks then.

So the rad had been installed in the core support last summer awaiting the car to finish assembly, and I had put some coolant in it that brought the level up about 4" from the bottom. I didn't fill it completely as I still had to finish the heater hose connections. Rad cap was installed and the drain fitting on the DS is actually a pipe plug.

About 2 weeks after I added the 1 jug of coolant, I noticed some had leaked out and had dripped onto the floor. I wiped it up and took a quick look and did not see an obvious spot where it was leaking from. Several weeks later, saw the same thing and wiped it up, intending to trace it later. Both times I saw coolant, I would estimate it was not more than 2-3 tablespoons, just enough to run down the core support bottom rail and drip 6-7 times on the floor.

Now the weird part...it stopped dripping and has been dry all fall & winter, then started again 2 weeks ago. So I bought a Stant cooling system test kit, finished all the heater hose connections, confirmed all hose clamps and drain plug was tight, wiped the leaked coolant off the the core support then pressurized the system to 18PSI.

The pressure did not drop AT ALL over a 4 hour period. There were no drips or wet spots of coolant that I could find.

WTH?? How can there be an intermittent leak under no pressure but no leak under pressure?

Anyone ever seen this before?

[25stevem]

My guess is that the drain plug you put in is not sealing well on its threads until you have pressure in the rad.

Even though pipe thread should not need Teflon tape on its threads I would drain the rad and put some on the plug and see what the out come is.

I would also look very closely at the bung while the plug is out as you may have split it by running the pipe plug in too far.
If so Aluminium is a easy repair!

[PunchT37]

Yep. Have seen that. It got down to 17 degrees here one night. Next morning saw a small puddle of coolant on the floor. Same place. Driver`s side radiator. Cold Case radiator. Pressure checked it. No leaks. Still has not leaked again. Petcock tight, hose clamps tight. Hmmm.

[25stevem]

I have also seen with aluminum rads where a hose clamp was way tighter then needed and crushed a hose nipple into a oblong shape..

[TxSportCoupe]

I’ve seen this also where different materials seemed to expand/contract at different rates and could cause what I deemed “low pressure, cold leaks”.
Usually the result of imperfect mating surfaces, not being tight enough, etc. It’s always a saga to figure it out and a 3 minute fix.
I chased a cold trans leak on my ride for two years. Changed trans cooler lines, pan, pan gasket, all manner of seals. It was the O ring on the modulator the whole time. And it had to get to the 20s in my garage to make it leak. And when it did, it would be a 3’ long 18” wide river of trans fluid. I was hot when I found it was a 10¢ O ring and I’d spent hundreds for nothing.


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[PunchT37]

Originally Posted by TxSportCoupe

I’ve seen this also where different materials seemed to expand/contract at different rates and could cause what I deemed “low pressure, cold leaks”.



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I believe that to be true in my case. Petcock into rad tank material differences along with cold conditions.

[TxSportCoupe]

Originally Posted by PunchT37

I believe that to be true in my case. Petcock into rad tank material differences along with cold conditions.

I bet with a single wrap of Teflon tape it never does it again. It will come up with something new. Because that’s what these cars do. They meet secretly at night and plot out how to trigger us! I’m certain of it. LOL!


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[mrennie]

Originally Posted by 25stevem

My guess is that the drain plug you put in is not sealing well on its threads until you have pressure in the rad.

Even though pipe thread should not need Teflon tape on its threads I would drain the rad and put some on the plug and see what the out come is.

I used Permatex liquid teflon thread sealant on the steel plug when I installed it. Unfortunately the rad support covers the plug so I can't get a good look at it.

The posts about different materials make sense. I managed to get an allen key into the plug and got another 1/3 turn so will see what happens.

Thanks everyone.

[PunchT37]

Originally Posted by TxSportCoupe

I bet with a single wrap of Teflon tape it never does it again. It will come up with something new. Because that’s what these cars do. They meet secretly at night and plot out how to trigger us! I’m certain of it. LOL!


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It hasn`t leaked a drop since then. IF I do wrap teflon on it, it`s sure to start some sh!t with me.

[zippy]

My years with large diesel generator engines, Like 4,200CI plus in displacement. When things get cold, they shrink. No matter HOW tight clamps and seals are on things, with long terms of cold sitting, leaks of coolant and oil always appear. Seals and hoses dry, and expand and contract with the ambient temps. Letting some dribbles here and there. Fire em up, Let em get hot and the rubber remolds itself to clamp and nipple, Good to go and will take a week or maybe a month of non running, to leak again. With you sitting idle for so long, I wouldnt worry. Once ou fire her up, then retighten everything once hot. Won't have any leaks unless she sits for a couple years

[dataway]

My GTO with freshly installed engine, trans, radiator etc. all juiced up didn't leak a drop for three months while shop temps averaged around 70 degrees ... now that it has been sitting undisturbed for months at about 45 degrees ... I see some drops under it. All of them showed up in the last one month of very cold weather.

Doesn't help that I go down a couple times a week and heat the shop up to 60 degrees for a few hours at a time. I can hear the lids on all the paint cans in the shop "oil canning" with the temp changes.

[Scott Roberts]

Originally Posted by zippy

My years with large diesel generator engines, Like 4,200CI plus in displacement. When things get cold, they shrink. No matter HOW tight clamps and seals are on things, with long terms of cold sitting, leaks of coolant and oil always appear. Seals and hoses dry, and expand and contract with the ambient temps. Letting some dribbles here and there. Fire em up, Let em get hot and the rubber remolds itself to clamp and nipple, Good to go and will take a week or maybe a month of non running, to leak again. With you sitting idle for so long, I wouldnt worry. Once ou fire her up, then retighten everything once hot. Won't have any leaks unless she sits for a couple years

Did you really say 4,200 ci diesel? What is that in?

[TxSportCoupe]

Originally Posted by PunchT37

It hasn`t leaked a drop since then. IF I do wrap teflon on it, it`s sure to start some sh!t with me.

Good call. I’ve opened up cans of worms unnecessarily, by fixing what ain’t broke. It will let you know when it’s time. They always do. I just pray I’m close to home when the notifications come. So far, I’ve been fortunate in that this car has done all of its puking and exploding at the house.


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[Sirrotica]

Originally Posted by Scott Roberts

Did you really say 4,200 ci diesel? What is that in?

Stationary engine used on oil field equipment, etc.

Engine.......Bore &..Cylinders....RPM.....HP
series .......Stroke
R5-V16.....17 × 21....V16.........514..13,618

[25stevem]

A common back up generator Deisel is a 16 cylinder model with 645 cid per cylinder, this totals out to 10,320 cid.
The earlier model of this 16 cylinder that was used in Tug boats especially during the change over period from steam to internal combustion was 567 cid per cylinder.
The 645 model was also made in a 20 cylinder version for a total of 12,900 cid.

You should see the Crank grinder needed to handle these !