Puking coolant....Bottom rad hose still cold???
 

Guys just a quick question, My car has been puking coolant out the overflow tank the last few times i have driven it. It has a low level in the APS overflow tank (like not far off empty) And it over flows after after 2-3 miles and some hard pulls.

One thing I noticed before taking the car out for a test run today was the OEM fans kicked in after 5-6 mins at idle and the bottom rad hose was still cold when the top rad hose was very warm?? This means the T stat has not opened ?? If the motor was circ'ing coolant but the T stat did not open then the car would be by passing the rad. Would this cause the car to puke coolant from the rad overflow if the T stat is ****ed and not opening?

Any ideas guys?

Could be that or a clog in the radiator.

It sounds like the t stat is stuck closed.

do guys think the stat could be part opening or not opening at the set temp? Im gonna replace it anyway but it must have a fault because the fans should not kick in till the rad/ bottom rad out let are hot showing the coolant is on circ via the rad?

When you put in the new t-stat, pull off the hoses from the radiator and pour water in the top and see if it flows freely out the bottom. This will just eliminate the possibility of a clog in the radiator.

You can always boil a pot of water and then dip the t-stat in it and see if it opens. It may help you sleep at night to know this is the issue.

I heard an interesting theroy that pulling too much timing causes the car to run hot and puke out the overflow. When my car was fresh built with the APS kit it used to puke out the overflow after hard pulls. The car eventually blew up, so now it doesn't do that anymore :ugh2:

the fans and thermostat are independent of each other

the coolant is still circulating past the coolant temp sensor in the back even before the thermostat opens and the fans are triggered by the temp sensor, so they will kick on when you reach the temp

^ what he said. the fans don't care what the t-stat is doing - when A/C isn't on, they're controlled by the temp sensor on the back of the upper coolant pipe (passenger side).

so what you guys are saying is the Fans kick in due to a high coolant temp that could be caused by the lack of flow through the rad due to a posable fault with the stat? I hope its just the stat, Cass the car does not just puke coolant on hard pulls, it just overflows out the breather hole on the APS overflow tank and keeps overflowing untill the car is switched off and cools down. I don't think its a HG problem I pretty sure its a cooling system fault so ill keep trying to track it down.

Thanks so far guys.

I hear what you are saying. Mine used to do the same thing, puke coolant out of the overflow after some spirited driving. Eventually it stopped happening. I just figured I had a bubble and it worked itself out.

Likely air in the system, try bleeding. Also could be failed thermostat or waterpump.

My question is... have you had the cooling system opened recently, or did this problem just come from nowhere after the car has been operating normally for some time?

The motor is on its run in at the moment, Its 4.7K rpm rev limited, It ran fine for 1300miles and then one day just over heated. It has a new OEM water pump but has used the stat of the donor motor I used for the built bottom end.

I doubt the water pump has failed as if i squeeze the top rad hose i can feel the flow going through it.

I bled the car again today with a spill free funnel and took the car out and no overheat/coolan puke after 10mins ball's out driving. I think the air pocket around the stat may have been the fault but can that really happen? Air pocket cause the stat not to open?

Thanks/

Overheating is a sign of air in the system and or a blown headgasket, same thing with coolant puking out of the overflow. In the case of a blown headgasket when a combustion cycle completes the pressure goes through the coolant system (heat and air cause spikes in coolant temps and the air pressure causes it to shoot out excessively)

Try bleeding the system (with the bleed screw) while the car is at normal operating temperature and see if any air comes out.

this happened to me. The air gets trapped behind the thermostat which means that no hot coolant is touching the spring therefore the tstat never opens.

I changed the tstat to a new one, same problem, back to old one, same problem. Then i got a spill free funnel and bled with that and no problem. Air behind tstat keeps it from getting the heat it needs to open.

Thanks for the help guys, Ill bleed the system again and then take the car out for a blast and see how it goes. Fingers crossed for me people!

20$ on napa or on amazon.com

get the spill free funnel. It's damn near impossible to bleed otherwise. I used to spend hours bleeding my car until i got that. Not a single drop of coolant spilled and it took less than an hour. I didn't have to do anything either, just run the car like normal and shut it off to let it cool and run it again. So none of the filling, blah blah, filling.

^ +1

Did mine earlier this week with a spill free funnel

Curious to see if this fixes your problem as Im having the same issue with my APS Extreme kit...

if you have a cold lower radiator hose then that 100% means the thermostat isn't opening.

from there you find the problem. stuck thermostat, bad thermostat, air behind thermostat causing it not to heat up and open.

The design is really simple so it's not likely the thermostat is bad. You can always pull it and put it in water to boil it to see if it opens.

My thermostat was opening forsure... I already replaced the thermostat last year so now im just going to remove it, pick up a better radiator, and have the fans controlled by the Proefi... I'll let you know if that fixes my problem...

No more bleed screw with the APS kit. The coolant T for the turbos replaces it.

Sounds like either air in the system or a bad t-stat to me.