VN running cold, not thermostat.

[savage1987]

Just changed the thermostat in my VN s1 V6 the other day, still running cold. Barely above the cold mark on the gauge.

Things I know so far:

Registers on gauge so I know it isn't the sender wire or the coolant temp sensor
Thermostat is new and factory temp so it isn't that
O ring is under thermostat like it's meant to be
Replaced housing seal, plenty of coolant in the system
Thermo fan operating correctly

Is there any chance I could have put it in backwards? Surely this makes absolutely no difference even if it is possible.. Other thing, I didn't bleed the coolant system afterwards and I read somewhere that this can trick the sensor a bit if there are bubbles in the system

Any thoughts?
Sam

[Morton]

Is it possible that the coolant temp sender is ready to be replaced? It may be fouled and sending a dodgy signal.

I don't think you would've put the thermostat in backwards.

It's basically impossible for the car to run, and be at or around 60 degrees for any sustained period of time - so you know that if you leave the car idling in the driveway for half an hour, and it still reads bugger-all on the gauge, that the gauge is not telling you the truth You just have to find out why.

[lowrida56]

fell the top of the radiator after you take it for a drive, if its really hot then you know its the sender or gauge...

[savage1987]

The gauge heated up when I let it idle on the spot even for just a couple of minutes. Got to around normal temp. As soon as I started going along the highway again it went straight back down to just off cold.

Assuming this rules out the temp sender

The same car, years ago now, had a thermostat that was stuck wide open.. it never even registered on the gauge until you sat in traffic for AGES on a hot day. They can run quite cold for quite a long time was like that for over a year when Dad had it.

[88GreenVN]

My 88 wagon ran cold as for years and years (from new) - temp gauge would only move 3-4mm off stone cold.

Would only get hot towing the van @ 80+kph on a 40 deg. day

[savage1987]

Dammit I want my car to warm up properly!!! lol I was so sure it was the thermostat playing up but apparently not

[88GreenVN]

Dammit I want my car to warm up properly!!! lol I was so sure it was the thermostat playing up but apparently not

Have you tested the sender properly? With a multi meter - if that the tool to use

[savage1987]

Nope it warms up fine and reads normal on the gauge after idling for a bit

I'm leaving the sender alone

[88GreenVN]

Nope it warms up fine and reads normal on the gauge after idling for a bit

I'm leaving the sender alone

Hmm probably best - that way you cant bust something that aint broke

[commsirac]

It would be good to verify what temp the motor is running at, perhaps your sender is ok, but nothing you have told us verifies that. Measuring the temp of the water that comes out of the top hose is the surest way, if you can get a infrared gun on to this then you will have some answers.

Thermostats that are put in backwards can work ok, once the are open to the flow, but in the critical time when they are heating up, the thermostatic element is on the cold side of the engine and may not heat up until its blown the bottom hose off or similar.

It does sound like you have another defective thermostat, can you detect that the top hose is getting warm well before the gauge hits the cold mark from cold start up?
What else could it be....dont know, suggest taking out the thermostat and seeing what it does when you heat it up in a pot of water.

[savage1987]

Oh yeah **** I should have mentioned earlier

LAST THERMOSTAT WAS WARMING UP JUST FINE JUST LAST WEEK SO IT'S NOT THE SENDER. GAUGE WAS READING FINE.


There we go, nobody is going to miss that important bit of info now

Sam

[DavoVP]

perhaps a dodgy thermostat. But if its any help my vp does the same thing, you leave it sitting, it warms up thermo kicks in. Stop start traffic, same deal, But as soon as i get rolling it sits just a tad of cold. On a realy hot day sits on 1/4.

I dont mind realy, i run gas and have never had a converter ice up. and its not chugging extra fuel because the car thinks its cold because the gas metering system is seperat from the fuel ( the ecu cant tell the gas system to dump extra because its cold )

In winter i would like it to sit up around normal so my heater actualy works lol, But its summer again, so ill leave it for a while :P Oh heater works just fine in summer In winter its all the windows up, idle for 10 mins to heat cabin then dont open the windows for the entire trip or you freeze ya balls off lol.

[savage1987]

My old thermostat was running it hotter than this one FFS... lol

Old one's cruising temp was just starting to come down so I figured get a new one and it'll run nice and warm again.. FAIL.

And not that it's related but my heater takes a good 10min of driving to heat up properly.

[88GreenVN]

My old thermostat was running it hotter than this one FFS... lol

Old one's cruising temp was just starting to come down so I figured get a new one and it'll run nice and warm again.. FAIL.

And not that it's related but my heater takes a good 10min of driving to heat up properly.

The heater wont work until the thermstat opens Is that right? Maybe not

[commsirac]

The heater wont work until the thermstat opens Is that right? Maybe not

No, that isnt right. The heater circuit is part of the circuit that circulates the water through the cylinder head with the assistance of the water pump. It will work regardless of whether the thermostat is open or not.
However, the heater being cold indicates that the coolant temperature inside the motor is low and this can only(well I cant think of anything else) happen if the thermostat is opening at too low a temperature and/ or the wrong thermostat is fitted and it doesnt set and seal the aperature properly.
Again, if the top radiator hose gets warm in the first few minutes of driving, the thermostat is not doing its job.

[vn calais manual]

is that 10 min of driving from a cold start? of course your heater has to warm up... it uses ur coolant which also has to warm up.

[88GreenVN]

No, that isnt right. The heater circuit is part of the circuit that circulates the water through the cylinder head with the assistance of the water pump. It will work regardless of whether the thermostat is open or not.
However, the heater being cold indicates that the coolant temperature inside the motor is low and this can only(well I cant think of anything else) happen if the thermostat is opening at too low a temperature and/ or the wrong thermostat is fitted and it doesnt set and seal the aperature properly.
Again, if the top radiator hose gets warm in the first few minutes of driving, the thermostat is not doing its job.

So the cold engine temp is a thermostat being stuck open and letting the coolant flow too much. OK got it - thanks.

[savage1987]

Yep heater comment was irrelevant. Sorry guys

[commsirac]

Yep heater comment was irrelevant. Sorry guys

?? I think it is relevant, its indicating that the coolant in the heater isnt getting hot, which is an indicator that the coolant in the engine isnt getting hot....which is an indicator that the thermostat isnt doing its job. Or did you heater have this problem before you changed thermostats?

[savage1987]

Heater's always taken a while to heat up. It's a VN

Thermostat is definitely running the motor colder than the old one. When I get a chance I'll put the old one back and that'll tell me if it's definitely the thermostat.

Sam