Earlier today, I changed my battery out, and adjusted one of the hoses leading to the AST. Unfortunately, it ended up pressing against the radiator fan. My stupidity, I guess. I realized the problem after driving a short distance, and then noticed that it had somehow popped down into place, and rested against the left radiator fan.

I rerouted the hoses and zip-tied them...but it was obvious that there was some friction there. It seems to be running at full speed...but I do notice that my temps are now at 90 degrees C instead of it's normal 83-87C.

The thing is that as soon as I shut off the car, the engine overheats! If I turn it off, then flick on the ignition, the temp gauge goes up to 114! Trying to start it at that temp is hard, and I'm not too sure it's good for the engine. The moment it starts, it goes back to normal though.

I'm flumoxed...any ideas what could be the problem? It's perfectly fine when it's running...only when it shuts off does it spike. And the car is running normally with no noticeable differences in power or idle. I'm also not dumping any coolant?

 

i would check the usual things, have you noticed any knocking? check the thermostat perhaps its failed and is restricting flow so that driving you are cooling the block somewhat but when you stop the very hot water is just rercirculating around the block and heat soaking near the sensor!?

 

My knock sensor normally never goes beyond 30 on the PFC. We just replaced the thermostat a few months ago. That would suck if it failed already.

How does the block cool itself once the engine is shut off?

Could it be that the hoses I'm using are a bit too long? I mean, they are kinda long. Could that affect it? The choke on my car has been removed (I had a pretty popular engine builder from Japan tune it, so I trust him...he just won a D1 Street Legal), so starting it always takes a little bit of throttle...it starts up fine when its at it's normal operating temp...so it's not really hard starting...just takes a little gas to get it idling...but it's done that since the reuild, and the compression is fine.

Grrr...I guess I'll just do a compression check tomorrow...but could that be a sign of failing coolant seals? That would suck. This engine only has like 1500 miles on it!

 

Don't worry about it - it's not an actual problem. The reason your water temp. is so high is because since the car is turned off, the coolant is just sitting and boiling in place without any circulation or actual cooling. As soon as you turn on the car and the water pump starts circulating the coolant (and the fans kick on) everything will be back to normal.

So in short, nothing to worry about.

 

I guess the problem is that when it jumps to like 114C...that worries me. Espescially if I try to to start it at that temp. It doesn't like that at all...it'll start...but not very well.

 

The temp should drop very quickly once you start the car, because then coolant will be flowing through the system instead of stagnating around the sensor.

 

Oh yeah...it does. It drops down like someone shoved a bag of icecubes down it...

Maybe I've just never noticed it before...but should it be hard to start the car at 114 degrees?

 

My car always seems a little harder to start when it is that hot too, but I think it is just because the engine reads the intake temps, and leans out the fuel mixture a little which I would think would make it a little harder to start. Maybe somebody else has more insight to this...

 

Yeah, hopefully that's the case. It just feels like this is a "new" problem. I really wonder if it's the rerouting we did with the hoses? Could it be that simple? At normal temp, it starts up fine. It's just at 114 degees, it's not so pretty.

I just want to add that my TPS sensor is bad, but Jin tuned the car to run without out it. That's why it's hard to start. He's an Apex'i certified tuner, too, owns his own shop in Japan...and tuned Drift Samurai's FC in D1...so I'm kinda trusting of his knowledge.

 

not to sound like an idiot here but while you were adjusting stuff in the cooling system, you may have introduced some airbubbles into it?? perhaps?? or by freak chance one of the pressure caps may have developed a leak. either way it sounds like you have air in your system which is causing earlier boiling resulting in your shutdown overheats.

maybe try burping the system a few times to see if it helps out.

 

In my (limited) experience the engine temps jumping like this shortly after shut down is perfectly normal... The engine bay is one massive heat sink with the hood down. As other people have already said, once you turn the car on and get things circulating again the temps will drop quickly. If you are that worried about it you could always pop your hood (if you park your car some place private..) or just drive moderately for a few minutes/miles before coming to a stop.

If I were you I would just pop my hood to let the heat escape immediately after shut down, or get/make a vented hood to do the same. I can't imagine keeping her cool is particularly easy in Hawaii.

The massive engine temps when sitting still is the same reason you will see temp increases in stopped traffic. This is when you roll down the windows and crank the heat!!

Are you sure the temps are a new problem in your car? or could you have just started to notice it...?

 

^^^ fendamonky's got it right - heat soak is VERY noticeable in FD's. And 114C is not that hot for the coolant in the engine right after shutdown - it's pretty normal.

As far as the hard starting, the AIT sensor heatsoaks and sets the mixture too lean to easily start until the incoming air cools the AIT back to reality.

Dave

 

Hmm...maybe it's just me being paranoid. Maybe I've never tried to start it back up, immediately after driving. Weird...thanks for the help guys...I think I'm going to go ahead and do some more upgrades to the cooling system. I have a base model, and sure would appreciate another oil cooler.

 

Get a vented hood and you'll be set!

 

I thought that a car that was difficult to start when hot was an indication of bad coolant seals?

 

Sometimes, but not a definitive symptom.

 

It can be low compression, or coolant on the spark plugs due to bad coolant seals.

That's in an extreme case, as in, 'man, the damn car really doesnt want to start.'

Even fresh motors won't fire up as nicely heatsoaked as they will stone cold.

 

get a vented hood, and turn on the A/C when it get near to 100*C. it will cool down the oil...also.

 

vented hood arnt gona stop heat soak, btw 110+ is normal once you shut of the car, Ive seen my car as high as 117

 

I have a similar problem with my car.

It always starts but you have to crank it over and hit the gas pedal a couple times.

Our cars do have hot start assists i think, so that might be an issue... i think?

 

I'm surprised we have a thread like this without mention of the fan mod.

That can run your cooling fans for ~10min after shutdown and helps limit heatsoak after shutdown. I don't think it does much to cool the coolant in the engine, but at least it keeps air moving into the engine bay and certainly cools the rad down.

 

yea I always, shut down the engine, turn ignition back on and then let turbo timer do its work for like 3-4mins

 

Which work is this? As has been discussed many, many times, coolant temperatures will climb in this situation because of lack of airflow through the radiator. Turbos timers are used to prevent oil coking in oil cooled turbos. Since FD turbos are primarily water cooled, turbo timers are pointless. After the turbo timer has done its work temperatures will still climb to 110C+.

The 110C+ temperatures seen soon after shutdown are caused by localized temperature increases due to a heat soaking engine block, which should be fairly obvious since temperature will drop back to < 90C within seconds after a restart. No automotive cooling system is going to be able to bring temperatures down 20C in that length of time.

 

didnt I say I shut down the engine first? Turn ignition back on so the turbo timer restarts, (not starting the car and just letting the thermos work to help the local heat soak)

 

If you are still running the HT12's than a turbo timer does more harm than good.