Normal for a FMIC to have fluctuating temperature?

[Bang876]

Is it normal for a heavily modify engine, especially one with a big rotated set up turbo to generate so much heat that it constantly changes the engine temperature. I am currently pushing about 20psi on my current tune but could easily swap my map to 25psi. Car is pushing slightly above 400whp and engine is fully built. On the highway i have been noticing the constant ups and downs of the temperature gauge. For example it would start at cold then gradually build up near to hot then reset back to cold. This process repeats over and over. In the city if i drive with a heavy foot it climbs up hot very quickly but never stays there long. I am new to the car and never owned a car with this much HP. I understand the fundamentals of how intercoolers work with turbo but since this is my first hands on experience i feel like something is wrong.. All the other cars i ever owned never had turbo and temperature gauge never so much as move. Am i being paranoid or is this normal for a such as this. Thank you

 

[Grinder34]

On the highway i have been noticing the constant ups and downs of the temperature gauge. For example it would start at cold then gradually build up near to hot then reset back to cold.

No, that doesn't sound right at all. It sounds like it could be a thermostat issue. How high on the temp gauge is it getting?

 

[STimedic]

You more than likely have a problem with your cooling system. Check your connector plugs, fan relays....I assume it's tuned, check the tune for the temp setting for the fans to come on. If all of those check out or have been replaced and the problem is still there, it's either the temp sensor or the thermostat. Temp sensor can be checked with a ohmmeter. If that checks out then it is without a doubt a faulty thermostat. Make sure you 'burp' the coolant system if you end up replacing the 'stat, otherwise bad juju will ensconce you.

 

[Bang876]

Thanks for the suggestions guys i will keep that in mind? I hope this is nothing major but I have been expecting something like this to occur so should have a around 5k to spend on any issues when i get back. The car has been seating idle for seven months now, what should be the first thing i do once i get back?

 

[Grinder34]

Bang,

The temp gauge in the car doesn't really have much/anything to do with the car being FMIC. The temp gauge is for coolant not for IAT. Anways, The fact that the temp can rise but also cool off quickly, seems to indicate that something is actively broken, rather than the cooling capacity of your car not being sufficient. If you simply needed more cooling, you wouldnt notice any problems unless you were pushing your engine. At that point you'd notice the temps slowly creeping up, until you eased off, and then they'd slowly come back down again.

It sounds like your heat-up can happen even in cruise, and that your temps can drop suddenly. That's an issue of something being broken! It sounds like your car's cooling system is staying "off" (like fans off, or thermostat closed) for too long, but once it turns "on" its effective at lowring the temps quickly. Before upgrading to a new radiator and fans, I'd either get the system checked out, or check it our yourself. Most of the things should be checkable with a few simple tools to save you some money. But if you dont fix/replace the broken bits, the problem may persist even with an upgrade!

 

[Vermont]

^ What he said.

Best bang for your buck right now since you already have a new radiator and fans coming is install them and while your at it, check out the temp sensor and see if it is working along with the fans. I am willing to bet you have no idea how to check the tune, so don't worry about that. Also this sounds much more like a faulty thermostat not opening at the right time. Does this problem happen under idle? Like if you let your car sit and idle will it over heat? Reason I ask is you can check to see if the thermostat is opening by holding the top coolant line in your hand and having some one sit in the car watching the temp gauge. If the temp starts to climb past middle and you don't feel any coolant in the hose that is in your hand (the top one) and don't see any coolant moving inside the radiator then you have a bad thermostat...

 

[Bang876]

^ What he said.

Best bang for your buck right now since you already have a new radiator and fans coming is install them and while your at it, check out the temp sensor and see if it is working along with the fans. I am willing to bet you have no idea how to check the tune, so don't worry about that. Also this sounds much more like a faulty thermostat not opening at the right time. Does this problem happen under idle? Like if you let your car sit and idle will it over heat? Reason I ask is you can check to see if the thermostat is opening by holding the top coolant line in your hand and having some one sit in the car watching the temp gauge. If the temp starts to climb past middle and you don't feel any coolant in the hose that is in your hand (the top one) and don't see any coolant moving inside the radiator then you have a bad thermostat...

the car while on idle gradually cool off and the temp gauge slowly goes to cool. The turbo timer i have is tune to keep the car on until the temp is at cool. I have notice in instances when I drive crazy and then pull up to a gas station and the car will literally stay for about 7mins before turning off.

 

[HolyCrapItsFast]

the car while on idle gradually cool off and the temp gauge slowly goes to cool. The turbo timer i have is tune to keep the car on until the temp is at cool. I have notice in instances when I drive crazy and then pull up to a gas station and the car will literally stay for about 7mins before turning off.

This sounds to me as though there might be a blockage somewhere in the radiator or somewhere else in the system or the water pump is not functioning properly. With out any load on the car the system is adequate enough to cool but when you add any load it is not efficient and it heats up.

I also note that in your OP you mention "heavily modified". In some cases this is the case with stock radiators on heavily modified cars to exhibit over heating under heavy driving situation but you usually only see this on the track.

If you have done everything as previously prescribed then you may need to upgrade your radiator if you haven't already.

 

[HolyCrapItsFast]

If you have an AccessPort or a Tactrix you can monitor and log the ECT? This will confirm the readings at the gauge and give us more of a clue as to what is going on.

The temperature should hover around 192* give or take and it can climb to fan temps (212*) while idling or driving heavy but it should never go over that. If you installed a lower thermostat then you will see allot of fluctuation between the thermostat temp and the fan temps and are dependent on outside conditions and driving conditions but again it should never exceed fan temps.