Problem with coolant flow?
 

Looking at the Lancer today I've found an issue with coolant flow, I thought the thermostat wasn't opening so I've replaced it today and refilled with coolant, I ran it in and couldn't get any decent temp on the return hose.
The feed was noticeably hot, but the return cold. The fans were running fast.

This has been an ongoing issue and I reckon has been affecting FE - the fans appear to spend a great deal of time running to me.

I made the coolant mixture stronger (50/50) instead of 33%, and similar results.

Today going for a drive I decided to stop pulse and gliding and instead keep the rpms to speed and this appeared to be bringing the temperatures down (noticed on the gauge the temp was down).

The theory is, when I pulse and glide, during the pulse the coolant flows fairly well, but the glide causes the timing belt driven water pump to spin too slowly to get the flow required and so the fans run a lot more often then they probably need to.

Q 1: What's going to be more efficient to use - fan electrical energy or pulse and glide?
Q 2: What solution exists to this problem?
I don't want the head overheating to the point it warps, but likewise there's little point in having the fans running if the thermostat hasn't opened (feeling the return hose it's not very hot, but low flow would also do that).

I'm looking closely at the sensor too - I had the car off and checked the temperature sensor with a multi meter and it's reading 0.08 to 0.10 kOhm, so the manual says 0.26 - 0.36 would be around 80 deg C - I left it some time - around 15 minutes or more, and it's dropped to 0.13 to 0.15 kOhm - not a great drop in temp, would it be ?

If you can put a ScanGauge (or maybe an UltraGauge??) in it you should be able to read engine temp digitally.

My Civic also doesn't cool the coolant much when at idle speed. I think that's pretty standard with an engine-driven pump.

Sorry I can't try interpret the temp sensor data. Radiator's return hose should feel cooler than the upper hose, definitely.

The fans definitely put a load on the alternator and thus on the engine. I avoid any setup that causes my (single) fan to run a lot. That definitely affects your fuel economy.

Have the radiator checked for partial blockages. I would think a 2004 model would still be good but radiators will transfer less heat when they get older, just like cholestrol in humans restricts blood flow. Also make sure the cooling system is "bled" properly if you have done anything that could cause an air pocket, which can also cause the problem you describe.

regards
Mech

good call OM, years ago I had the same air lock on a fiero, got rid of the air and no more overheating the head. now for my 2cents if all is found ok how about drilling a bigger bypass hole in your spare thermstat and test that, it will flow more cool anti freeze at a lower speed on the pump

We'd flushed the radiator before hand yesterday.

The sensor right now is reading 0.98kOhm, which according to the factory manual is about 40oC - it's been off all night, so I don't think that's right (or the manual is wrong).
I'll swap out the sensor, and get a higher flowing thermostat and see if that fixes the issue.

EDIT: The manual was wrong (it refers to two sensors in the same year - the sensor appears correct based on the right values).

As for air in the system, I can't see any bleeder screw to release air, and I did run the system in with the cap off through to operating temp and then some, and then filled until it dropped no more.
I don't think there is air in the system but I'd like to find a way to be sure :)

With the cap off, squeeze the upper rad hose repeatedly.

That was done too, it won't have any air in that part of the system.
It's got to be a flow issue, the stat opens and the pump is spinning off the timing belt.

Electric Water Pumps (EWP)

These have the right idea, shame about the pump price though - a bit high.

toc I just reread your post and you say the supply is hot and the return is cool could you have the flow reversed , some cars run the cool water to the head first and some to the block first whats the manual say. I think some cars run both fans when the ac is on .

My driving today just proved it.
There's nothing wrong with the sensor, the fans appear to be working as intended (i'd love a current switch to determine for sure!).

The design isn't great:
The sensor before the thermostat drives the coolant temp gauge, the fans have a fan controller that operates on PWM.
The thermostat opens at 82oC.
The fans appear to run around 82 and up (just guessing).
The fans try and control the one coolant sensor.

There's not enough flow through the radiator when I pulse and glide,

There's two possible ways I can fathom that would be better:
- A temperature sensor at the top of the radiator - the fans modulate to maintain that temperature at like 75.'
- An electric pump, get rid of the thermostat, and the pump runs as needed at speeds as needed resolving the flow issue. Since the thermostat is out of the equation and the flow maintained correctly, correct temperature conditions are maintained.

The first would control the fans better then using the one in the block - but to put it together I need to find the known values that the fans turn on / off at (I hope it's higher than 82!).

Better flow will result in an even temperature so an electric water pump would be nice, but this presents a problem - The timing belt would still be driving the old pump, I'd need to remove it to get the best results which means removing the load that pump puts on that belt and maintaining the pulley in place - the only way I can think of that would do this is cutting the fins off the pump giving it no coolant to move.

This is all up in the air though, I don't realistically know how much fuel it takes to pulse and glide and run it hot (but i'd still be concerned about the head with low flow).

still not making much since . does it overheat at idle, the system should cool no matter what. unless 1. blown head gasket, 2. oiling problem 3. air lock