Cool heater in the cold weather

[A900ss]

This is my first winter with the tvr so I may be expecting too much but my heater is very cool when moving.

It warms up nicely when I get to some traffic lights but anytime on the move, it's cool. It certainly made the roof off driving today less pleasant than normal.

I know the temp gauges on these are renowned to be useless but on the move (single A roads) it is reading about 60 degrees, sometimes lower. The same driving in the summer was 75/80 ish degrees. When I get to traffic lights and I feel warmth coming from the heater, the temp gauge has moved to circa 70 degrees as the car isn't moving in the cold air.

Reading the forum it looks like the heater does cool a bit on the move but they are still normally effective. Likewise 60 on the move seems too low.

What is the best way to check if the thermostat is stuck open without actually taking it out?

Any other thoughts most welcome.

(PS - I don't suspect an air leak or the heater valve as the heater does get hot when the car isn't moving)

Edited by A900ss on Saturday 23 November 16:22

[TV8]

My money is on an air lock or not opening fully at the heater valve. Plus cold air getting in under the drivers door seal and through the holes in the inner seal behind the carpet!

[QBee]

Mine does exactly the same. But once warm it stays warm.
So if you want a warm journey get going, and after ten minutes stop with the engine running until the fans cut in - won't take long.
I went for a drive this morning. Four miles to a village pub. Parked for ten minutes while I made a menu enquiry, then three miles into town. Within a few seconds of joining a traffic light queue I heard the fans cut in and the heater was toasty.

[A900ss]

QBee, mine gets warm at the traffic lights but then cools down (heater and temp gauge) when moving again.

PS - I checked my swirl pot just in case and it was full to the brim.

[Harrytsg]

This has the hallmarks of the thermostat stuck open.

For the sake of 10 mins to change and 3 days to bleed, its worth changing it to at least eliminate.

[MethylatedSpirit]

Harrytsg said:

This has the hallmarks of the thermostat stuck open.

For the sake of 10 mins to change and 3 days to bleed, its worth changing it to at least eliminate.

This is your most likely culprit. Listen to this person.

[A900ss]

I assume the test is to hold the top hose and feel if it warms up slowly with the engine (thermostat stuck open) or gets warm suddenly (thermostat working correctly).

[anonymous-user]

MethylatedSpirit said:

This is your most likely culprit. Listen to this person.

Must agree that's what cured mine.

[TV8]

A900ss said:

QBee, mine gets warm at the traffic lights but then cools down (heater and temp gauge) when moving again.

PS - I checked my swirl pot just in case and it was full to the brim.

Not sure if the serp is the same as the pre-serp for bleeding, but my pre-serp needed to have the front up-high on jacks to get all the air out.

[BIGMIKE1]

Mines similar to QBEE once the temp gets up its not too bad but it struggles to get up if I just drive off and get on fast moving roads, plus I already put a new thermostat in and it did improve but still seems to cool massively when on the move in cold weather.

[sheel]

Buy a cheapy laser thermometer from Maplins, you can point it about around the engine to get some temps, mine was running cold, swopped to an 88 deg stat last year, was out today and the gauge was well down in the cold air but the heater was toasty, normally see 75 to 90 in the summer but she was well down again today, got to the stage of not worrying, car is happy and heater is hot,,,,,,,good enough

Rich

[ChimpOnGas]

Definitely an airlock, no matter how much you've convinced yourself it isn't.

I've been through all this and now have a heater like a real car

Actually to be fair the chimaera heater is damn good, but at speed a tiny airlock can mean the hot coolant bypasses it almost completely.

Get the air out, and get your excellent heater back.

I was out doing 100 leptons on the M25 today and I actually had to turn the heater down a bit as the cabin was roasting.

My Canems software (which is 100 times more accurate than the TVR gauges) tells me I idle at 90 degrees, and even at speed on a chilly day like today the coolant never falls bellow 80.

Bleed it up mate, and you'll have a lovely toasty TVR winter

[A900ss]

What's the process for bleeding?

[ATG]

A900ss said:

What's the process for bleeding?

Stand on head in passenger footwell to try to see what's going on behind the dash.

Sneeze.

You will you are bleeding profusely.

[ChimpOnGas]

A900ss said:

What's the process for bleeding?

Jack the car up at the front as high as you can, support with axle stands.

This helps to force a solid column of water through the heater matrix which sits relatively lowish in the system.

Put the heater onto full so the heater valve is fully open creating the maximum flow around the core.

Undo the brass plug in the swirl pot & insert a big funnel to create a header of coolant.

At this point you can also remove the blue cap from the header tank and half fill.

To be hones the header tank is less critical, keep in mind you're trying to get rid of the air and by it's very nature air will always try & find its way to the highest point.

Start the engine, fill the funnel, raise the revs lightly and squeeze the the top hose to the swirl pot.

Keep the revs up, and watch the air bubble out as you squeeze that top hose.

Once you're happy all the air has been expelled, remove the funnel, replace & do up the brass swirl pot plug.

Lower the car, drive at speed with the heater on full to test.

Feel the difference

PS: There's also a bleed nut on the corner of the rad, starting the process here is not a bad idea.

Remember, the last bit of air will normally be at the highest point, so work your way up the system to burp it out.

[BIGMIKE1]

^^^^^^^ this is how I've always bled mine since reading daves method, only thing I'd add is I find once its all cooled down I bleed the rad again and just top up the levels again then usually ok.

[A900ss]

Just started her from cold and then held the top hose to see if it got warm very fast (as in thermostat just opening) or warmed up gently (as in thermostat stuck open).

Hose warmed up gently and even when it was warm, water temp gauge still hadn't moved from bottom.

Looks like my thermostat is stuck open.

[Goaty Bill]

Agreeing with all of the foregoing regarding airlocks, thermostats and rad filling.

David's method here is also documented elsewhere, but his would seem to be the most comprehensive and fully descriptive I have come across.
I will add that bleeding air via the screw in the top corner of the radiator (as mentioned in his 'PS') has proven an essential part of the process in my case.

With the cold weather, my standard, decrepit and disastrously inaccurate gauge tells me that I am about 90 at a standstill, 80 in moving traffic, and as low as 60 on motorway cruise, but my heater has remains hot (though it does get a fraction cooler after a while on the motorway).

[Chuffmeister]

I didn't get on very well with the above method and ended up with more coolant on the drive than in the swirl pot, especially when the car got warm. From what remember, I started by filling the swirl pot and expansion tank and leaving the caps off until circulated. I replaced the cap on the expansion tank and I allowed the water to circulate a couple of times. I then topped up the swirl tank and ensured that the expansion tank retained about an inch in the bottom. I bled the air by using the radiator bleed screw and the hose on the side of the intake manifold. Seems to be working fine.

[Goaty Bill]

The big funnel is an essential part of this process.
I have attached a large flower pot to the top of mine, holds around 3-4 litres for the running up period, when water and bubbles can get a bit active