3 replies to this topic

[fotostars]

Hey guys,

so I finally installed a fancy (meaning expensive and accurate) pressure sender on the bypass of the coolant in the back of my engine (1.8 on a '97).

Goal is to monitor if I have a leak or lost of coolant.

I am running a stock Thermostat (new) and a 19PSI Koyo cap (new) on a Koyo Radiator if that helps...

Outside temp was close to 100deg.

 

 

I've wired it to my Traqmate for reliable monitoring.

Sitting on grid, the idiot light (set at 2.5PSI) would regularly light up.

Now I get towards the end of the race and my warning light goes off.

 

I think I understand what's going on on grid (the cap must be releasing to the overflow tank, though it's supposed to hold at 19psi, it seems to give at below 15psi).

But less understanding of what's happening during the race.

 

Attached graphs showing temp on top and PSI at the bottom for both the time I sit on grip, and the time during the race...

 

Any help understand what's really going on would be great. I don't understand why the pressure is not holding up during the race. And may have a complete misunderstanding of what's going on sitting on grid.

 

One last point, It doesn't look like I'm loosing any water along the way. Everytime I check, I have water up to the neck of the radiator filler.

 

Thanks for your wisdows guys! It's driving me a little crazy.

 

 

 

 

 

[steveracer]

You have a small leak somewhere among the 27 hose connectors, plugs, caps, etc.

 

Radiator is full because it draws from the overflow as it cools.

 

 You could also have a defective cap out of the box, it happens. 

 

Also make sure the mating surface for the cap is CLEAN. Even a hair could fubar it.

 

Hot and under pressure the upper hose should be hard as 16 yr old pecker...

[Danny Steyn]

NOPE - this is just a sensitivity setting. On my H2O pressure warning lights, the ones created by Bill Agha, as soon as I come off a hard run, such as the cool down lap or if a full course yellow comes out, the H2O pressure trend would be downward, and the light would come on, despite the static pressure being high.

 

With an adjustment the light remains green. I suspect your unit will have something similar

[Duncan]

Have you put a pressure tester on the radiator and made sure it holds pressure?  You can have tiny leaks that don't result in coolant loss but can affect the ability of the system to hold pressure. 

When I first installed my water pressure sensor it took awhile for the engine to build pressure and the light to turn off.  It would also flicker in grid sometimes as well.  Temperatures were fine and I wasn't loosing coolant.  I drove it for three race weekends without any issue.  When I put a pressure tester on it I noticed a very small leak (1-2 psi over 10 minutes).  I found a slight leak in a rear bypass hose (oem spring clamp). 

 

After that, the system pressured much faster, the light turned off sooner, and it stopped flickering in grid.

 

So while it might be normal behavior, I'd want to be absolutely sure you don't have a small leak.  The pressure tester is the only way to know for sure.  Also, I've had an OEM cap fail, so if the system does hold pressure, I'd change the cap just to make sure.  It's cheap and you should have a spare anyways.

 

Duncan