Temperature and fast idle

Hi guys, I have 2 weird anomalies just popped out of my 2000 5th Gen and wondering if you can help me isolate the problem.

Firstly, my fan use to come on at 103 degrees celsius (217F) and stay on till 98 celsius (208F). However, just recently the fan only turns on at 110 celsius (230F). What can be wrong? I've just flush and changed the coolant. It was working well for 3 weeks and suddenly this.

Secondly, the fast idle on my bike will usually return to normal idling rpm once it hit 55 celsius (131F). However, now it continues to fast idle till 80 celsius (176) or more.


Could these 2 problems be related? T-stat stuck? Electrical faults?

Tks!
hansen

 

If your rad's are getting hot below 150F your t-stat is stuck open. As your temp goes past about 180 to 190 you should notice the t-stat open and the rads start getting hot. If your coolant temperature is changing somewhat normally it may not be your t-stat. When you flushed the system did you make sure you got all the air out? Air in the system can cause weird problems. You can also test the thremo sensor to make sure it's giving you an accurate coolant temp reading. Good Luck!

Action

 

Sound like ECT sensor, engine coolant temperature sensor. But I was under the impression that the 2k model had a wax valve Idle Air Control valve. I am not sure, my 98 has a manual idle boost, looks like a choke lever. Doubles as a redneck cruise control at slower speeds . Could be air in the system as well. Need to double check that first.

 

00-01 have a "fast idle wax unit". Mines out. Luckly I found the wax unit part for $18. Just need to order it.

 

Tks guys. Just came back from a trip, will rip the fairing and do the checks.

On a side note, any bad things will happen if I remove the T-stat completely? I live in the tropics, and temp do not go below 20 degrees celsius.

 

It will take the bike longer to warm up causing it to run on the rich side. Some of the guys here are saying with no tstat your bike will over heat. One of my friends took his out and I don't remember him over heating but he used his bike mainly for fun on the weekends and not as a daily commuter.

Action

 

With my t-stat stuck open and in the city my bike had no problems reaching 230F. I find the reason being the coolant was just rushing through the rads to fast. It'll probably be worse with no t-stat cuase there would be a hint of resistance.


The only people that I know that dont run t-stat are drag racers. They start, warm up, go down the strip, turn around and turn the vehicle off. I can see why they dont cuase their HIGH horsepower engines dont take long to warm up anyways.

 

So your saying that a properly working tstat would close at high temps to restrict coolant flow? No way! Any vehicle can exceed its recommended temperature even with a 100% functioning coolant system. I had the same thing when mine was stuck open. If it was warm out or I got stuck in traffic it would heat up. All that proves is that you are exceeding your systems ability to exchange heat. The VFR's side mounted rads are not the greatest at shedding heat anyway and the fans not much help in low speed conditions.

Action

 

Would close at high temps??? What the hell are you talking about. I never said that.


T-stat or no t-stat a bikes gonna get hot sitting still on a hot day. I'm talking about when the bikes in motion. The pump is spinning as fast or faster than the engine is. So no t-stat means the coolant is hauling ass thru the system and not being cooled properly. If this wasnt true then nothing would be running a t-stat.

 

In manual under troubleshooting, if the engine temp is too high, the T-stat could be stuck CLOSED; if the temp is too low, the T-stat is stuck OPEN. Hence we can conclude that the T-stat valves open to increase the cooling (allowing more coolant flow to radiator).

Question is, is it possible to 'overcool' our bike? Without the T-stat coolant will flow faster (maximum rate) and hence achieve maximum cooling capacity.

A cool engine is always better right?

My pov is that T-stat are for countries that has very low ambient temp. Just like why you use anti-freeze in the coolant. I'm using Waterwetter, which has no anti-freeze properties at all.

 

If you leave out the thermostat it will take longer for the bike to warm up, if it warms up completely at all. On a bike with O2 sensors, i.e. 2k+ models, the bike will never reach closed loop fuel mixture operation, thus causing the bike to run rich all the time, as well as cause premature wear on the engine due to the low temps. It is not physically possible for the bike to overheat without the thermostat as the main purpose of the thermostat is to allow for faster warmup and regulation of coolant flow at low temperatures. Without the thermostat the coolant flows unrestricted all the time. I do not recommend running your bike without a thermostat because the bike was designed to run at a predetermined temperature to maximize horsepower and minimize engine wear. However it is better for the engine to run on the lower side of that temperature spectrum.

Oh yeah, and the fuel injector pulse is determined by the ECT and IAT, so the fuel computer will assume the bike is not warmed up and will dump more fuel in the cylinders.

 

You got the close/open backwards.


You need a thermostat. Plain and simple.


Teh faster your bike warms up, the faster it gets into closed loop and runs correctly.

 

Sorry if I misunderstood you post. You said "With my t-stat stuck open and in the city my bike had no problems reaching 230F. I find the reason being the coolant was just rushing through the rads to fast."

The only thing in the system that would slow the flow of coolant is the tstat partly, or completely, closing.

Anyway, I hope everyone has a good Christmas and a better New Year

Action

 

Thanks guys. I've bleed out the coolant and top up + burp the system. Now it seems to be back to normal!

Learn something new: when you bike topple coolant leaks out, you might wanna check there's no air in the cooling system.

My guess is that air is trapped at the wax unit, causing both anomalies?