Engine running too cool ?
Moderators: User administrators, Moderators
- wibble
- Registered user
- Posts: 25
- Joined: 13 Sep 2007, 15:37
- 80-90 Mem No: 4228
- Location: Defford, NR pershore, worcs
- Contact:
Engine running too cool ?
Checked thru wiki and searched loadsa post but could one of you techy geniuses please help me out cos I still ain't sure what my problem is, if indeed it is one.
Has been running fine. Today took her out for a 20 mile run. Temp gauge only just made it it white area. Luke warm heater output. Touching bottom of rad, it too only felt luke warm. Do I have a coolant system issue here ? Engine seemed to be running fine. Coolant LED flashes for 10 seconds on start up, that's normal isn't it ?
Has been running fine. Today took her out for a 20 mile run. Temp gauge only just made it it white area. Luke warm heater output. Touching bottom of rad, it too only felt luke warm. Do I have a coolant system issue here ? Engine seemed to be running fine. Coolant LED flashes for 10 seconds on start up, that's normal isn't it ?
-
- Trader
- Posts: 3117
- Joined: 08 Oct 2005, 19:36
- 80-90 Mem No: 1
- Location: Huddersfield, WeYo.
- Contact:
What engine?
Sounds like you have no thermostat, or it's stuck open but a van of 1983 vintage it could be lots of other things.
Temp gauge lying.
Faulty temp sender.
Faulty voltage regulator
dodgey wiring.
take the temp sender wire off the sender and earth it, the gauge should shoot up to the end of the scale, if it doesn't, probably a dah fault.
If it does, either sender is goosed or theres a mechanical problem, probably lack of thermostat or dodgey thermostat.
Does the temg gauge get cooler when going down hill and warmer goin g up hill?
Sounds like you have no thermostat, or it's stuck open but a van of 1983 vintage it could be lots of other things.
Temp gauge lying.
Faulty temp sender.
Faulty voltage regulator
dodgey wiring.
take the temp sender wire off the sender and earth it, the gauge should shoot up to the end of the scale, if it doesn't, probably a dah fault.
If it does, either sender is goosed or theres a mechanical problem, probably lack of thermostat or dodgey thermostat.
Does the temg gauge get cooler when going down hill and warmer goin g up hill?
- wibble
- Registered user
- Posts: 25
- Joined: 13 Sep 2007, 15:37
- 80-90 Mem No: 4228
- Location: Defford, NR pershore, worcs
- Contact:
Hi simon
Its a 1.9 DG wasserboxer running on LPG. Only just recently rewired dash & checked it out to OK.
Didn't really notice gauge position on hills exactly but it did move around slightly.Whether this was on an incline or not I can't remember.
I off to Hastings tomorrow (5 hour drive) Can I do this with reluctant thermostat ?
What is significance on gauge position in relation to road gradient as I shall look out for it tomorrow ?
Its a 1.9 DG wasserboxer running on LPG. Only just recently rewired dash & checked it out to OK.
Didn't really notice gauge position on hills exactly but it did move around slightly.Whether this was on an incline or not I can't remember.
I off to Hastings tomorrow (5 hour drive) Can I do this with reluctant thermostat ?
What is significance on gauge position in relation to road gradient as I shall look out for it tomorrow ?
-
- Trader
- Posts: 3117
- Joined: 08 Oct 2005, 19:36
- 80-90 Mem No: 1
- Location: Huddersfield, WeYo.
- Contact:
The thermostat is there to helpt the engine warm up quickly by stopping the flow of coolant to the radiator until the engine is hot enough.
The heater circuit is not part of the thermostatically controlled circuit, so you should have warm heaters if the engine is hot enough regardless of thermostat position.
The thermostat is also there to enable your engine to run at a steady temperature, as steady temps are required for the longevity of your engine, basiclly all the metal components will wear less if they are not subject to constant temperature variations. hot cold hot hold et..
If the thermostat is stuck open, which it sounds like yours might then then engine will take an age to warm up as, as soon as the engine starts producing any heat it is instantly cooled by the radiator, not good for your heaters and not good for your engine.
basically, your thermostat is closed, you start the engine, as the coolant temp rises the thermostat opens slowly, you go up hill then engine gets hotter because it's working, they thermostat open more, to flow more coolant to get cooled by the radiator.
You go down hill, then engine does less work, runs cooler and the thermostat should close to keep the engine at optimum temperature.
if you have no thermostat, you will see this variation, if you do have a good themostat you shouldn't notice it because between the header tank cap holding pressure ijn the system (pressurised water has a higher boiling point) a thermostat to control the amount of flow to the radiator and the radiator cooling fan to keep the temps down if they creep up your needle should sit bang on the middle of the gauge with little or no variation.
Hope that helps.
The heater circuit is not part of the thermostatically controlled circuit, so you should have warm heaters if the engine is hot enough regardless of thermostat position.
The thermostat is also there to enable your engine to run at a steady temperature, as steady temps are required for the longevity of your engine, basiclly all the metal components will wear less if they are not subject to constant temperature variations. hot cold hot hold et..
If the thermostat is stuck open, which it sounds like yours might then then engine will take an age to warm up as, as soon as the engine starts producing any heat it is instantly cooled by the radiator, not good for your heaters and not good for your engine.
basically, your thermostat is closed, you start the engine, as the coolant temp rises the thermostat opens slowly, you go up hill then engine gets hotter because it's working, they thermostat open more, to flow more coolant to get cooled by the radiator.
You go down hill, then engine does less work, runs cooler and the thermostat should close to keep the engine at optimum temperature.
if you have no thermostat, you will see this variation, if you do have a good themostat you shouldn't notice it because between the header tank cap holding pressure ijn the system (pressurised water has a higher boiling point) a thermostat to control the amount of flow to the radiator and the radiator cooling fan to keep the temps down if they creep up your needle should sit bang on the middle of the gauge with little or no variation.
Hope that helps.
- wibble
- Registered user
- Posts: 25
- Joined: 13 Sep 2007, 15:37
- 80-90 Mem No: 4228
- Location: Defford, NR pershore, worcs
- Contact:
Simon, you were spot on with your description of what would happen if my thermostat was on the blink. Temp rising on hills and then falling off on straights. Pint of the amber stuff to you.
Cracked open the thermostat housing yesterday to replace it and found...... sod all except the bottom flange of what once must have been a thermostat. Looks like a previous owner must have had some sort of overheating issue which they solved by hacking the thermostat to bits and putting back the remains.
What gets me is why this wasn't apparent when I first bought the van.
Still new thermostat going in shortly so I can get off to the airshow at fairford next week.
Cracked open the thermostat housing yesterday to replace it and found...... sod all except the bottom flange of what once must have been a thermostat. Looks like a previous owner must have had some sort of overheating issue which they solved by hacking the thermostat to bits and putting back the remains.
What gets me is why this wasn't apparent when I first bought the van.
Still new thermostat going in shortly so I can get off to the airshow at fairford next week.
- ermie571
- Registered user
- Posts: 4970
- Joined: 11 Oct 2005, 11:11
- 80-90 Mem No: 2129
- Location: Minster-on-Sea, Kent: Member 2129 07784052288
oh how I love reading technical......mine behaves exactly like yours, Wibble
so I guess I need a new thermotat too.
How easy did you find replacing said thermostat?
we have a 2.1 lump bolted to 1.9 pipework, so may be a little different, but any tips would be useful!
Em
x

How easy did you find replacing said thermostat?
we have a 2.1 lump bolted to 1.9 pipework, so may be a little different, but any tips would be useful!
Em
x
2.1 DJ 1990 Caravelle (died and gone to heaven)
2.0 AGG (1997 ish) 1984 transporter LPG
2.0 AGG (1997 ish) 1984 transporter LPG
- wibble
- Registered user
- Posts: 25
- Joined: 13 Sep 2007, 15:37
- 80-90 Mem No: 4228
- Location: Defford, NR pershore, worcs
- Contact:
Bolts holding housing together came off surprisingly easily. Issue was separating the two halves. Did in end by hammering a screwdriver in between bolt housings. Other than that was very straight forward. PS don't forget to drain coolant first otherwise you get a free shower.ermie571 wrote:oh how I love reading technical......mine behaves exactly like yours, Wibbleso I guess I need a new thermotat too.
How easy did you find replacing said thermostat?
we have a 2.1 lump bolted to 1.9 pipework, so may be a little different, but any tips would be useful!
Em
x
- wibble
- Registered user
- Posts: 25
- Joined: 13 Sep 2007, 15:37
- 80-90 Mem No: 4228
- Location: Defford, NR pershore, worcs
- Contact:
Was terrified of it but you know what, she went with no issues even overtaking stuff too !!!!!!!!1664 wrote:wibble wrote:as anyone in the Midlands knows that's one long steep climb up the Cotswold escarpment.
I know it well - never been up it in my camper though.....

- Ian Hulley
- Registered user
- Posts: 12661
- Joined: 11 Oct 2005, 08:08
- 80-90 Mem No: 1323
- Location: Wirksworth, Derbyshire ... or at t'mill
Don't get too excited yet pepes! My £300 Mondeo had no thermostat when I bought it and was running cool. I replaced the stat and brought the running temp up to scratch and promtly left a trail of smoke everywhere I went due to slack pistons and the cats pee oil they recomend for the Zetec. Clever of the previous owner don't you think! I had budgetted for a short engine though so no problem. Dream machine otherwise though as we are almost invisible to fuz and yobs alike as a pair of silly old codgers in a sad old ex travelling saleman's car. And the parts are cheap as chips.ermie571 wrote:Ian,
thnaks for the warning....hopefully not going JK/GSF still trying to get vw parts to answer the phone!!
Em
x
Cheers Ken
Well-timed silence hath more eloquence than speech.
"A quiet shy boy who took little part in games or sport"
88 High top 2.1 WBX
"A quiet shy boy who took little part in games or sport"
88 High top 2.1 WBX
- kevtherev
- Registered user
- Posts: 18832
- Joined: 23 Oct 2005, 20:13
- 80-90 Mem No: 2264
- Location: Country estate Wolverhampton Actually
wibble wrote: one long steep climb up the cotswolds escarpment.
aaaahh the Cotswold escarpment, they say that time stands still up there.
post offices... public phone boxes..cottage hospitals...morris minors... village fetes with a tombola and people off to church every sunday...
*sigh*
AGG 2.0L 8V. (Golf GTi MkIII)