cooling system

[mark_n2]

I have coolant leaking from the Reservoir or somewhere in that area. What is strange is after sitting a week, the system is still pressureized which tells me the cap and reservoir are fine. From the reservoir a line runs to a metal cylinder. This has stains around the top, but not enough to account for the amount of fluid under the car, wrong location as well. Can someone tell me the function of this cylinder. I can see how it could be the expansion tank, but what I dont see is how this cylinder is vented. I was going to remove this wknd and figure the system out, but was hoping someone could give a pointer. Car runs fine, never runs hot, no oil in the coolant and no coolant in the oil so not concern about a blown gasket.. i hope.

[FWB]

the cylinder is a overflow tank, look under the water pump there is a hole in the casting on the snout. a leak there will usually be after running and system will remain pressurized. however a pressure tester will take the guesswork out.

[mark_n2]

Thanks, I checked the water pump- seep hole is dry. So, the cylinder is the catch tank. How it vented?

[FWB]

i don't think it is under pressure, if you have an expansion tank its not. the overflow will simply catch overflow when the expansion tanks cap gets over-pressurized. start the motor bring it up to temp then shut it off. at this point the cooling system will make its most pressure. now is the time the leak will rear its ugly head.

[RedBarchetta]

Mark, take a finger or two and feel under the water neck/thermostat housing at the front of the intake manifold that the expansion tank connects to. If it's damp then that's your problem. Also check the tightness of the two thermostat housing bolts. They shouldn't be torqued too tight (it is aluminum!), but vibration has been known to loosen these. Also a good look from underneath with a flashlight will usually allow you to "follow the trail" and you can see where the water is originating from better. Good luck!

-Dean #747

[WildBill1965]

Check the thermostat housing, sometimes they will leak after sitting for a while may need to be tighened up a little or a new gasket. Don't get carried away as this is usally aluminum

[mark_n2]

Thanks, I plan on going under the car this wknd.

[Blas]

Assuming you have a Superformance, and have the usual arrangement… (Your SPF car number would help here)…
And just so we have our terms correct here; The Expansion Tank is usually connected to the engine and then a big hose from it goes to the radiator. The Overflow Tank is connected to the Expansion Tank via a small hose and may only have a small drain valve on the bottom.
The staining on the overflow tank is probably just some excess coolant – there probably is e a small vent hole drilled on the top of the overflow tank where it came from.
Do you have the black painted brass expansion tank or the stainless steel expansion tank?
If it’s the black one, the usual problem is fatigue on the bottom hose connection to the tank because of the vibration of the engine and poor original design of the tanks bracing, I’ll just bet the tank brazing is cracked allowing more vibration on the tank flange. Look here first for the problem.. The stainless tanks have had very few problems. A good radiator shop can refurbish this Expansion Tank quite reasonably. The SS tanks cost major $$$.

[mark_n2]

Thanks again,
SPO2561
Roush 327R
SS Tank

[mark_n2]

that should read 427R

[Blas]

I would probably clean everything up with "Simple Green" and watch it.
If you recently replaced or topped-of the antifreeze you may have overfilled the system and the leak you see may only be the system looking for equilibrium...The expansion tank should only be filled up to the hole in the tank divider inside with fluid...put you finger inside the tank and you can feel the hole in the divider.

[madmaxx]

my guess is it where your water pump bolts to the block. Notorious for leaking there. See if it is not damp in the little valley on the driver side adjacent to where the pump bolts to the block. If it is there the best solution is to add some bars leak to the cooling system, half a bottle is fine and the leak will be forever gone. You could replace the gasket but more than likely it will rear its ugly head. GM, Ford, Chrystel all instruct to add leak sealant anytime the system is flushed to catch these nuisance leak.

[dont]

Be sure and check ALL of your hose clamps. A slight leak can run down a hose to a weird spot to drip.

[Got the Bug]

Originally Posted by madmaxx

my guess is it where your water pump bolts to the block. Notorious for leaking there.

Especially the bolt that holds the alternator on and passes through the water pump. I had to replace an alternator on my Roush and when I removed the bolt coolant started dripping out. As soon as I snugged the bolt back up, the drip stopped and I haven't had any problems. Agree with Blas, clean it up and then investigate (coolant can go everywhere). If you can't find the source, you can try a dye kit and light.

[Night Enforcer]

Mark n2, I have the same set up as you have. My system started leaking within the first 500 miles. The culprit was the hose clamp on the outbound hose coming out of the expansion tank heading towards the radiator. It would not tighten enough to seal the connection. It felt tight and would not tighten any more but still leaked. I replaced it with a new hose clamp, tightened it up and had no other problems. The spots on the floor did not correspond at all with the leak, as the coolant would drip down and follow a weird path before dripping on the floor. My son also has the same set up on his car and had a problem too, but it was the next clamp towards the radiator on his that was not tight enough and would not tighten. He replaced his and has had no other problems.

Good luck

[mark_n2]

Thanks, I didnt get a chance this wknd to check all the suggestions provided but hopefully will get around to it next wknd. I'll post an update once I find the leak.

[danc30]

Another question is, why is it still pressurized after sitting for a week. I just went through an issue like this and it was pushing coolant past the cap due to a reaction of UV dye and watter wetter in my system.

Do you have UV dye in the system?

[mark_n2]

UV dye- nope. I am confused by the pressurization as well. I checked on the cap but did not see a PSI rating? Can anyone tell me this specification?

[FWB]

caps vary but it should be around 18 psi