Printable View
My FF water temperature is pretty much on target while I'm on the track. Typically around 190 degrees while driving it hard.
But, as soon as I pull into pit lane the temp rises rapidly to 250 degrees and the coolant system pushes coolant into the overflow tank and spews fluid out of the tank and through the radiator cap.
Any ideas on what is happening? Why are we seeing this when slowing down into pit lane?
The obvious difference between the two situations is decreased/no airflow at pit lane speed vs on track, and decreased/idle speed of water pump.
If your water pump impeller has broken/eroded/not so flashy, it might be pumping "good enough" at raised/on track rpm, but not pushing enough at idle.
The other thing is air flow through the rad - it might be enough at 100 mph, but can't get through the rad at slow speed - bent over fins, buildup of crud between fins, other type restriction(s)...
Hope that is of some assistance, GC
Would a small electric fan to turn on in pit lane be feasible ? Very low current draw. ..
Not an unusual problem at all. Most likely you are still pushing the car hard for that last lap before coming in the pits, so the heat energy stored in the engine block and head is still near its peak.By suddenly slowing down to pit entrance speed and then stopping, all that heat energy has to go somewhere, which of course is the water. But since you are now going slow or almost stopped, there is not enough airflow through the radiators to reject it faster that the speed that it is being absorbed from the engine, so the water gets hottter and hotter, boils, and starts going out the overflow.
The cure is to run the last lap slower to give the engine time to cool down a bit. It will probably still puke a bit, after you stop, but as long as your overflow/return bottle is big enough, it shouldn't be a problem.
Glenn & Richard. A prime example of why I lovr Spex Speed :thumbup::thumbup:
Also, check that your Rad Cap is holding the pressure that listed.
I looked at the radiator and it is not obstructed by any debris. It seems to be fine.Quote:
Originally Posted by glenn cooper
However, I have thought about the water pump. When the water temp is high and I rev the motor the temp decreases pretty rapidly making me think that the pump may not be at full efficiency.
Thanks for your input.
Good point. I recall that when we ran the car at Mid Ohio I took slow cool down laps and did not experience over heating. But, at recent events I drove it hard before pitting and this is where I experienced the problem.Quote:
Originally Posted by R. Pare
I put a new rad cap on that is 16 psi and the problem persists. Is 16 psi enough? Would a slightly higher psi cap, say 18 psi, be enough to solve the problem?Quote:
Originally Posted by kea
If the cooling system is adquate to provide proper cooling at speed don't bother making the water pump "more efficient"...it's just going to rob more horsepower pumping more water than needed while racing.Quote:
Originally Posted by Ralph Z.
Slower cool down lap. When in the paddock coming off the track keeping the revs off of idle helps cooling and oil pressure.
I would think that for your vehicle, 16 lbs should be enough.
Another thing to check is that ALL of the air entering the radiator ducts is actually going through the radiators and not partially escaping through open spaces around the radiator. Blocking them off will not cure the boil-over problem you described, but will help keep temps down a bit better while out on the track.
The problem is not the cap rating - you just need to realize that it takes time to cool a racing-hot engine before coming into the pits and parking it.
To help a bit on restoring the water to the system if the engine still boils over a bit, add in an adequately sized coolant recovery bottle and its hose.
If your water level is low, when you slow to idle speed, the block pressure and flow are insufficient to keep the head full of water. The pressure cap will help but also install a coolant recovery system and be absolutely anal about evacuating all the air from the water system.
Any air in the system will make it impossible to maintain block pressure when you stop the engine. This allows the water to boil and over heat the engine.
And, removing air from the system means running the motor without the cap for a period of time?Quote:
Originally Posted by S Lathrop
No.Quote:
Originally Posted by Ralph Z.
You simply fill the system to the top of the cap, and install the cap. The caps have a relief valve to allow air in as the engine cools. The coolant recovery system catches any water that overflows and returns it as the engine cools. The system brings coolant in from the recovery tank.
Got it. Thanks.
That's why in the olden days it was not called the 'final lap' rather, it was a COOL DOWN lap. :)Quote:
Originally Posted by R. Pare
Ever notice even the Pros run that final lap really slowly? It isn't just so they can wave to the crowd better :)
The air intake of the Alexis nose does not appear to be overly generous. So, too, with my Crossle 20F. My procedure for the cool down lap is NOT to go too slow or fast. I coast down to a speed equivalent of 3rd gear at 3500 +/- and try to maintain it until slow down and turn off into the paddock. At or about that rpm, the engine doesn't have to work very hard, yet the speed is enough to force cooler air through the radiator. Go much slower and the air through the radiator will surely be inadequate. Once within the paddock, no more than 30 sec at "no faster than a person can walk", otherwise shut'r down. Why? Temperatures persistent around that high a temperature might just possibly warp the head. Sounds to me that just perhaps you have more of a problem than you realize. How long has this problem occurred? As expensive as a new aluminum radiator may be, that solved all my problems. The original radiator while in good condition, simply could not dispel the built up heat in the block, especially if you are/were doing a lot of drafting. The old original radiator is being saved for those who wish to have original equipment. GL. I've been there. :o
Here is a photo of the radiator. Looks like it is a replacement and pretty hefty.
I like your cool down process. I'll be trying it out at the next outing. :thumbsup:
Quote:
Originally Posted by Ralph Z.
The assumption is that the cap is at the highest point in the system. It should be in a properly designed cooling system.Quote:
Originally Posted by S Lathrop
Other times packaging of the system and aero means compromises are made (ask any 6th gen Honda Civic DIY'r) getting air out of the cooling system is very important, and simply filling to the top of the cap won't get it done.
The Alexis is a good looking car. :thumbsup:
In filling its system, you might look into raising the rear slightly to make sure that no air can get trapped in the radiator. Assuming that the upper hose is the water exit from the radiator, you shouldn't have a problem with air getting trapped while running. Even so, it wouldn't hurt to have a bleed line back to the header tank.
When filling the system up frest, use water and water wetter, not anti-freeze. Make sure that there is a bleed hole in the thermostat itself. Run the engine up until the thermostat opens, then shut it off, let cool a bit, and remove the radiator cap to see if the water level has dropped. If it has, add water and repeat until it stops dropping.
[QUOTE=R. Pare;402158]The Alexis is a good looking car. :thumbsup:
:D:D:D
Looks great Ralph!