Revs rise when changing gears on 4th Gen VTEC Lude?? - Honda Prelude Forum

CDR_UK · 10-22-2003, 12:47 PM

Tonight I changed the coolant in my lude, and on the way home from work, I noticed for the first time, that between gear shifts the revs were rising like 1-200rpm by themselves before dropping.

Is this related to the coolant change or just a coincidence? When I bled the system, it looked like a steady stream of coolant from the thermostat, but I could be mistaken and it needs bleeding again.

Another thing is that after refilling the coolant, I started the engine with the rad cap off, and waited at least 20mins, but the fan didn't even cut in. The temp gauge was just reading normal, and I had to get home so couldn't wait anymore. The performance on the way home was good - same as usual as far as I could tell.

When I got home I let it idle for 2-3mins, but no fan, and temperature gauge was still at normal.

The outside temperature is quite low - maybe 6C max.

I did a search and found that some other people on this forum and a UK forum had the same behaviour from their ludes - but nobody mentioned changing their coolant.

Can anybody shed any light on this please?

Cheers,

Chris

h22a193 · 10-22-2003, 02:20 PM

dont think the rising of the rom has anything to do with the coolant. Did you mess with your throttle cable at all, if its too tight it could so this, but i doubt collant change ahs anything to do with it.

4bidden · 10-22-2003, 02:32 PM

Start the car and let it idle for a few minutes them bleed it from the thermostat.

yield · 10-22-2003, 02:42 PM

ya, probably a little air still left in there... bleed away

as for the fan, I think a lot of 4th gen fans don't work without ill effects. Don't think I've ever heard mine.

CDR_UK · 10-22-2003, 02:54 PM

Cheers guys,

The fans definitely used to come on in the summer, maybe it's just too cold outside now - but it was idling for more than 20mins and just sitting at normal temperature on the stock gauge. *touch wood* it's never ever ever been above the halfway mark.

I'll try bleeding it in the morning and let you know. It seems like too much of a coincidence for the revs to rise straight after changing the coolant.

Chris

prelude styl · 10-22-2003, 07:20 PM

depending on how you drive it's actually normal. It's like when you press the clutch pedal in to shift and while letting off the gas you're a little slow and are still giving it a bit, it'll rev up like that. I sometimes notice it happening when I'm driving, but can stop it at any time by how I let off the gas when shifting.

CDR_UK · 10-22-2003, 11:44 PM

Thanks for the suggestion, but it seems hard to believe this is normal - it means I changed my driving style after I flushed the coolant?

I bled the sytem again just to be sure that there's no air trapped.

After letting the car idle for 10mins, the temp gauge was in the normal position, but the lower radiator hose was still almost cold - like the thermostat wasn't open yet.

Driving for 5mins (no VTEC), I checked the lower hose again, and it was warm, but by no means hot.

According to the helms, normal operating temperature is reached when the fan has kicked in twice. It also states that the thermostat starts to open at 70c and is fully open at 90c. The fan should cut in at 92c-98c.

It's pretty cold outside around 6c. Could it be that my engine has simply not gotten hot enough to fully open the thermostat, and that's obviously why there's no fan?

BTW, both fans work fine when I switch on the A/C.