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coolant behind driver tire under floor pan

4K views 23 replies 12 participants last post by  vincentm 
#1 ·
I've had a slight coolant leak with my STS since I got it. I've noticed water under it behind the drivers front tire a few times. Today I realised it was coolant. I looked and don't see an over flow hose coming off the pressure tank. Where is it coming from?
 
#3 ·
There is no overflow hose on a 5th gen Seville, theres just a flat spot on the top of the tank towards the firewall that any water pushed out of the over flow drips off of. Its either coming from the cap, or from a crack in the tank itself, possible that theres a hole in the line that attaches to the bottom of the tank, but that doesn't happen too often.
 
#4 ·
Get a pressure test kit and track down the leak. I had my coolant tank develop a pin prick hole that would spray coolant all over once the system was pressurized, the plastic can get brittle over time and the coolant will find a way out if it finds a weak spot. Picked up a new tank at a wreck yard for like $20.
 
#6 ·
Its odd, some times this car leaks coolant and some times it doesn't. No rime or reason to it that I've been able to figure out. I know one place it leaks is from the water pump housing from time to time, but not consistently. And I've noticed the spot I questioned about a few times but with the weather where I live I thought it was just frost and ice melting after driving the car. Till today,
when I looked and investigated I saw coolant dripping from the sub-frame under the driver floor board.

I'll try grabbing the coolant pressure tester at work during lunch tomorrow and see if I can find where it may be originating from.

Tire Alloy wheel Automotive tire Wheel Vehicle
 
#8 ·
Water pump shaft seal, water pump capsule to housing seal, water pump housing seal or (the dreaded) crossover gaskets ... are all in line at about that position. Are you sure it's coolant, though (use a paper towel to figure out the color)? Both transmission line and power steering return lines go along that sub frame rail.
 
#10 ·
Is your vehicle equipped with a sunroof?
That could be also one of sun roof drains.
Is a bit too far back to be coolant anything...unless it runs along something before dripping.

Check if you have dripping in the first 20 minutes after turning the engine off, or the dripping shows up much later after that. If is later is not the overflow.
 
#11 ·
Is your vehicle equipped with a sunroof?
That could be also one of sun roof drains.
Is a bit too far back to be coolant anything...unless it runs along something before dripping.
I do have a sun roof, but it is def coolant. I got down and put my fingers in it. I checked under the hood at the same time and didn't see any coolant under the hood other than on top of the water pump housing which I'm aware of and is at the front of the car.
I'm wondering if maybe its the crossover leaking from the bottom towards the firewall. At night I can see a little steam infront of the drivers head lamp after turning the car off, pop the hood and nothing. No coolant any where, no steam.

I love this car, but I'm use to my old SBC's, and I'm having to learn all the odd leak locations and quarks with theses N*'s. I really appreciate your all's input and this forum.
 
#12 ·
These cars a pretty well known for cracking the radiator end case right in front of the upper radiator hose connection on the drivers side. They crack and weep steam. At first you can only see the steam under the right temperature and humidity conditions but later it starts to come out at the edge of the hood right at the front corner and you can see the steam on the top face of the hood. a leak from the radiator end case usually dries before it can drip on the ground though. From the size of the puddle in your picture I would think its either from the surge tank, or the back crossover manifold gasket.
 
#16 · (Edited)
Your radiator core is aluminum; the end tanks are thermoplastic. They're held on with a skrillion bent fingers - and there's a formed seal ring between the core ends and the tanks.

The tanks seem to develop hairline cracks with age. Although a radiator shop CAN replace only the end tanks, the best bet - with a 14 year old radiator - is to replace the whole enchilada.
 
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