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Matt110

Member Since: 29 Jun 2014
Location: UK
Posts: 685

Those with Thermotop C, in use experiences

Having now got a functional thermotop C, thought I'd ask if it's performance is as expected, as I've no idea this is the only one I've ever had.

All observations made at 7 degree C ambient (or thereabouts).

Before heater:
Cold start. No heat till 10 minutes into drive after driving up a reasonable engine load hill. Heat then available until vehicle idles or the throttle input drops off for long enough that the block cools down. Then goes cold again.

After heater:
With no pre-heat, heat, although minimal, valuable within minute of start-up. With pre-heat, clearly heat available permanently. Never blows cold even from startup.

Where does your temperature needle get to? Appears heater goes into 50% duty before the needle gets to "normal" (recognise this is calibrated to represent a wide range of temperatures to avoid customer concern), and even if left for extended periods of time, with engine off, the engine never reaches "normal" gauge temperature, i.e. half way. If you then drive it.... It does after a few minutes, but will drop to 1/4 again. It's like the heater has bought 1/4 gauge increase on any pre-heater level!

That what everyone else finds?

11th Apr 2021 9:21am

drakes

Member Since: 09 Oct 2009
Location: Consett
Posts: 114

2004 Defender 90 Td5 HT Auto Belize Green

In short yes. I find if using the preheat then the glowplug light goes straight out but as you say the temp gauge does not get to normal temp from the thermo top alone.

11th Apr 2021 4:03pm

SJM2018

Member Since: 06 Jul 2018
Location: Bristol
Posts: 296

2011 Defender 90 Puma 2.4 XS CSW Aintree Green

Depends on ambient temp, whether the heater control is set to hot/cold, whether the fan is engaged and the run time.

It was 3 degrees here this morning, the heather control was set to hot, the fan was off and it had been running about 30 mins.

The temp gauge indicated that it was about 2/3 operating temp when I started the engine.

The temp then dropped to 1/3 operating temp (presumably as the cold oil cools the engine / I put the fan on to warm the cab), but recovered and was at op temp a little over 10 mins after setting off. 2011 CSW XS 90

11th Apr 2021 5:35pm

nosnibod

Member Since: 15 Aug 2007
Location: West Midlands
Posts: 370

1998 Defender 110 300 Tdi SW Bronze Green

I had a Thermo-Top C in my Td5 for years and my experience was pretty much as described - 2/3rds of the way to normal operating temperature ‘on the gauge’.

The Webasto kicks in when the water temperature drops below 60C and cuts out at about 72C, so it all make sense when you think that most diesels run at about 82-86C.

I’m looking forward to the FBH in my new 300tdi - this time I’ve gone for an Eberspacher for a variety of reasons but they all operate on the same principles. I’m looking forward to jumping into a warm and defrosted vehicle in the mornings - even if that’s much less frequently after the pandemic had changed my working practices for the better. Dave
Green Goddess - 1998 Defender 110 300tdi

11th Apr 2021 6:55pm

Matt110

Member Since: 29 Jun 2014
Location: UK
Posts: 685

Thanks all that's superb feedback. I guess what I'm really pleased about is having rebuilt mine before fitting it is working as we'd all expect it to.

Left it running on the drive till it tripped out earlier just so I knew it would and all is well. Five minutes later it tripped in again as the block started cooling.

11th Apr 2021 7:33pm

SJM2018

Member Since: 06 Jul 2018
Location: Bristol
Posts: 296

Fair play rebuilding and fitting yourself - I had a look, but it was too daunting.

I ended up buying the specific Defender version and having it professionally fitted which cost an arm and a leg!

Even with the cost, I still feel very smug when I go out on a frosty morning and the truck is ready to go, while the neighbors are scraping ice / demisting their windows; so you must feel super smug sorting it yourself!! 2011 CSW XS 90

11th Apr 2021 8:28pm

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 8205

2011 Defender 110 Puma 2.4 USW Stornoway Grey

Mine gets to 40 deg after 15mins running and around 60 degrees after 30mins. Working from 5 degrees ambient.

Based on 3 vehicles each having a thermo top fitted to 2.4s, Reading coolant temp off scanguage. Heater on full heat, fan off.

When its 15/20 degrees ambient, 40/45deg coolant temp after 10mins, which is perfect for the heat exchanger for onboard shower.

None of mine drop from horizontal temp reading once up to temp though unless it's 3ish degrees or less. If yours comes down so quickly maybe check thermostat Cheers

James
110 2010 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

11th Apr 2021 9:34pm

SJM2018

Member Since: 06 Jul 2018
Location: Bristol
Posts: 296

Cheers jst, I'll have a look tomorrow morning.

Is it easiest to start the truck (after the webasto gets up to temp), let it run for a minute or so and the gingerly touch the rad?

If the thermostat is shagged, I think I'll go with one of the 82 degrees version (PEL500110). 2011 CSW XS 90

11th Apr 2021 9:46pm

Matt110

Member Since: 29 Jun 2014
Location: UK
Posts: 685

JST that reference to none dropping below normal midpoint on the gauge once up there, what is the vehicle heater doing at that point are you using it or is it turned off? Wondering if you used the vehicle interior heater you'd then get the drop in gauge reported temperature I/we seem to be getting.

11th Apr 2021 10:21pm

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 8205

I use my webasto to preheat prior to start or to maintain heat if parked up, engine off. , I don't run it when the engine is running. ( two water pumps at different speeds)

I get a slight drop in temp after startup, less than 10deg but it climbs back within couple mins driving. Heater set to full heat but I don't turn fan on until engine is at operating temp. It then stays horizontal unless 3sh deg or less and sat in traffic.

I leave fan off to concentrate heat to the block. Heated seats and an air top provide cabin warmth. I also keep engine revs lower until fully warmed up. Cheers

James
110 2010 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

13th Apr 2021 8:06am

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 8205

took a photo this morning to show all the stats from my thermo top. it was run for 25mins prior to starting.

Click image to enlarge Cheers

James
110 2010 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

16th Apr 2021 6:23pm

Matt110

Member Since: 29 Jun 2014
Location: UK
Posts: 685

Superb shot, thanks, that's really reassuring as that's exactly where I'm ending up.

16th Apr 2021 6:28pm

Matt110

Member Since: 29 Jun 2014
Location: UK
Posts: 685

Where does it infer its intake air temperature from, is it the MAF or post turbo?

Just wondering how reliable that would be to use after a while driving.

16th Apr 2021 6:50pm

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 8205

not sure it doesnt change a great deal with engine use/heat. only time you see an increase not expected with ambient is when stopped turned off after a run with heat under bonnet. (as to be expected) Cheers

James
110 2010 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

16th Apr 2021 8:19pm

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