Spraying coolant at WOT- but only in second gear

[pridemore54]

So I haven't had a ton of time behind the wheel of my cobra but both times I have done a WOT pull from a second gear roll (Results in wheels spin for a min before grabbing), I have a small amount of coolant spray from the engine reservoir cap, out the hood heat extractor, and onto my windshield.

With a 2.9L Whipple and a 4lb lower pushing ~23.6lbs of boost at WOT, I'm worried I'm lifting the heads and pressurizing the coolant system. Worth noting, I have a Moroso coolant tank and cap.

However I have done about 10 WOT pulls from third to fourth gear, same boost, with no coolant spray. If I was truly lifting the heads I would expect to see spray no matter what gear, correct?

Hoping the cap is the culprit considering the details. After the second coolant spray, I pulled over and rotated it several times to try and find a spot where it felt the tightest and left it there (It's one of those locking mechanisms that will just kinda tighten up then give so you can rotate it forever). After that I didn't have a chance to try it again at second gear and it's been raining here nonstop so I can't take it out again any time soon.

Any thoughts or suggestions?

 

[01yellercobra]

Are you 100% sure it's the engine coolant and not the intercooler side? A lot of times the o-rings in the intercooler manifold start to go bad and start bleeding boost into the intercooler system.

 

[pridemore54]

Are you 100% sure it's the engine coolant and not the intercooler side? A lot of times the o-rings in the intercooler manifold start to go bad and start bleeding boost into the intercooler system.

Next time I will take a picture to share but I'm fairly positive based on the residual spray I saw around the coolant cap if that makes sense. When I looked at it I didn't have a doubt in my mind that is where it came from and it lines up pretty much perfectly with the driver side heat extractor.

 

[01yellercobra]

I was just making sure. You can get a cooling system pressure tester and see if it holds pressure. If it does, get a new cap and try again. If it doesn't, then it's time to dig deeper.

 

[pridemore54]

I was just making sure. You can get a cooling system pressure tester and see if it holds pressure. If it does, get a new cap and try again. If it doesn't, then it's time to dig deeper.

Sounds like a good plan of attack. Hopefully the testers at harbor freight are decent. I remember seeing one on sale there for $40 a couple weeks ago

Appreciate the input man

 

[01yellercobra]

I think you can also rent them from Autozone using their loan a tool program.

 

[LV_Ford_Fan]

I had a cap that would not hold pressure. It tightened with a click OK. Turns out that the rubber seal inside was warped just slightly but enough not to seal properly. I just bought a new cap.

 

[P49Y-CY]

you alluded to it in your post and hopefully it is not, but that is a symptom of a head gasket issue.

it can be unpredictable and not happen every time you go wot. but the way to rule it out for sure would be to test your engine coolant for combustion gases. best of luck with it

 

[TitanSvt]

I'm having the same issue with WOT. Just had a mechanic give suggestions, after telling him that's my ONLY symptom (no head gasket symptoms at all) he immediately said cavitation..essentially meaning the water pump is spinning too fast and causing the water molecules in the coolant to break apart and turn into air bubbles...he said the fix would be to slow the pump down, either by larger water pump pulley or new pump all together that spins slower or has less fins. Haven't had time to do that yet but, just a thought.

Sent from my SM-G998U using the svtperformance.com mobile app

 

[DSG2003Mach1]

I'm having the same issue with WOT. Just had a mechanic give suggestions, after telling him that's my ONLY symptom (no head gasket symptoms at all) he immediately said cavitation..essentially meaning the water pump is spinning too fast and causing the water molecules in the coolant to break apart and turn into air bubbles...he said the fix would be to slow the pump down, either by larger water pump pulley or new pump all together that spins slower or has less fins. Haven't had time to do that yet but, just a thought.

Sent from my SM-G998U using the svtperformance.com mobile app

A bad tank, bad cap, head gasket, or as mentioned it’s actually from the intercooler and could be that tank, cap or the o-rings

 

[MG0h3]

The only in 2nd gear thing strikes me as a crack or bad seal/cap.

Most inertia sending the fluid back and up towards the cap.


Sent from my iPhone using svtperformance.com

 

[pridemore54]

I'm having the same issue with WOT. Just had a mechanic give suggestions, after telling him that's my ONLY symptom (no head gasket symptoms at all) he immediately said cavitation..essentially meaning the water pump is spinning too fast and causing the water molecules in the coolant to break apart and turn into air bubbles...he said the fix would be to slow the pump down, either by larger water pump pulley or new pump all together that spins slower or has less fins. Haven't had time to do that yet but, just a thought.

This could make sense.

With second gear revving the water pump much faster than the other gears, it could be causing cavitation that I wouldn't see under the more tame rev climbs of the higher gears.

If the pressure test and exhaust test don't show anything, I'll replace the cap and see if that helps. If not, this could be a good next step.

 

[DSG2003Mach1]

In the 20+ years the mod motor has existed I have never in my life heard of an overspun water pump causing a problem. I have a higher flowing water pump that’s also being run by a 10% OD crank pulley and spin to 7k with no issues

Also that’s a pretty poor understanding of cavitation to start with

 

[holiks03cobra]

When mine was spitting coolant at wot it was a head gasket issue/lifting the heads. Get a tester and check for exhaust gases in the coolant.

 

[pridemore54]

Haven't had a chance to grab a tester thanks to the holidays and upcoming travel plans.

However I did get the cobra out and tried a couple more pulls from second gear. No spray at all. I'm hoping this means it really was just the cap needing to be tightened to the right spot.