Need some advice about this issue:

engine is fully build run about 2kmiles tuned on dyno and not overheated on the dyno. using mishimoto fan and aluminum half size rad.

the car always lost coolant after build and there is no mixing not in coolant and not in oil few leaks were fixed but it still lose coolant no leaks found (never looked on the water pump maybe it has small leak). no smoke from exhaust.

on a regular drive car never overheated but after few pulls and then slow drive needle starts to rise up never passed the 3/4 fan is working and it is not going down (on high way temp not climbs) when i start the heater temp goes to his right place little bit under the half.

What do you think is the problem from where to start?

Thanks!

 

if you can get your hands on a cooling system pressure tester then that would make finding the leak a lot easier.

 

yes, will have one in 2 or 3 days, hope to find a leak

Do you think this is the reason for the main issue in my first post?

Thanks

 

its a good possibility. its the first logical place to start, then go from there.

 

it happened also when coolant level was ok,
of course finding the leak is a good start but does a small leak with no missing coolant can cause overheating?

 

up...

 

if it spikes after a boost pull then the boost and compression and heat is making its way into the coolant passage and making it airbound. the coolant loss is from the added pressure pushing the coolant passed the rad cap

 

by that you mean i have a leaky head gasket or some crack?

if so why i don't see evidence of mixing?

can air pass from iacv to coolant?

also never saw coolant coming out from the cap. (checked while it happened)

it happens only after boost like spike and due to the needle movement it really looks like air.

Thanks!!

 

are you running a coolant over flow?

 

yes

 

if compression was entering the cooling system you would notice it in the over flow. it would be filling up with coolant if not over flowing and possibly boiling

 

make sure your fan is spinning the right way
loosing coolant can result in lost of system pressure

 

overflow is filling with coolant but with very small amount ,this is ok, no over filling.

i will try the pressure test to find any leak.

 

Fan spin to the correct side.

made Pressure test and there is no leaks or pressure lose ,it stays stable on 16-17psi.

when engine is working pressure gauge needle is not bouncing (HG or warped head/block symptom) and pressure build in the system.

i bleed the system went for a hard ride and it happened again (no magics).

when it happens 2 thing will make temp back to the correct level drive on high way or working heater.

the rad is a aluminum came with new 1.1bar cap, any chance its the cap that not hold pressure??

What do you think??

 

up...

 

by a better fan something shrouded and sealed at the radiator...

Do a poor mans leak down, warm the car fully with the radiator cap OFF, once thermostat is open and car is FULLY warmed up put cap back on. boost on it a few times, pull over check to see if the radiator hoses are hard, if they are headgasket is probably leaking...

Just because its not mixing coolant into the oil or pushing coolant badly or smoking etc etc doesnt mean you dont have a headgasket issue...

 

Cap tested also and found ok.

Allthogh i will test it with new one.

Then i will try to replace thermostat and flush the system and
clean rad.

If it want help i will do new HG.

Will update

Thanks