Cooling... help

[anonymous-user]

Bought the car a couple of months back (1995 400HC Serpentine), I checked the fans come on and off. I have done some jobs on her over the last couple of weeks and one them beeing changing the coolant. What has developed now is a temp gauge flapping about, and as soon as I pull up the fans come on and stay on, they only go off when I pull away or lift the bonnet up!! Now the embarassing bit, when I bought it I checked that fans come on and off, but I remeber it was with the bonnet up! thought nothing more. This is what I have done so far;

Drained flushed with Holts rad flush, then back flushed the rad, and refilled, axactly 33% glyco/de-ionnised water.
Bled the rad, topped up the header, and the expansion stays at half full.
Bled the manifold via a tube with a stop end conveniently placed next to the thermostat/temp sensor (?)

I give up now...! running round she sits at 70 so all ok here. On tickover at standstill, the fans just stay on (and on)and she goes to about 80-85 no higher.

Help?

>>> Edited by anonymous-user on Wednesday 9th March 21:04

>>> Edited by anonymous-user on Wednesday 9th March 21:04

[Nuggs]

Sorry Dobi, not sure I understand. It sounds like:

• your fans come on when you're static; and

• they go off when you get some cool air into the engine bay, either by pulling away or lifting the bonnet up

Have I missed something, but isn't that a good thing, preventing the car from overheating while standing still (most people have the opposite problem!)?

Anyway, it does sound like your thermostat and/or otter switch could be up the creek. It might pay to try fitting the Leven cooling kit.

Really sorry if I have misunderstood your post

[mongoose]

as you gauge sits at 70 on the run,then either your thermostat is ok(most likely)or its suck open,so i wouldnt change this first.id try the otter switch though,as this seems the most likelt culprit if your sure the system is bled completely.personally i wouldnt go mad and buy the leven kit.i found the water wetter makes no noticeable difference whatsoever,and you can buy all the parts cheaper at your local motorfactors.ps.i think its better to run 50/50 antifreeze/water,it gives better protection and you never know when you might only be able to get water in an emergency!!

[deeen]

I'm with Nuggs, I don't think you have a problem. Mine sits at 90 when idling after a run, but only manages 70 / 75 on a motorway run at this time of year.

I wouldn't worry, panic slowly if it approaches 100, panic a bit quicker if it goes past that temp!

[parrot of doom]

Hmmm, my thermostat is about 80-85 while driving, and 90+ when stationary. Fans work ok though.

[M@H]

Dobi, how is your driving style..? If you are running the car at reasonable/highish revs just before you stop then then the fans will spring into life pronto as the heat you have created has got to get dissapated. I tend to cruise gently to a stop outside my house, adopting the principal of the trackday cooling down lap... if on a trackday you come straight off track having been caning the car and stop the engine, you'll as often as not have a big puff of steam from under the bonnet as the car boils the water in the block. (this is not to be reccommended)

Matt.

[Nuggs]

parrot of doom said:

Hmmm, my thermostat is about 80-85 while driving, and 90+ when stationary. Fans work ok though.

Parrot, IIRC the early Chims (i.e. non-Cerbera-style front) do tend to run a little hotter as not so much cool air gets through the front dam.

[mongoose]

Dobi said:

On tickover, the fans just stay on (and on)and she goes to about 80-85 no higher. Help?

this is a problem.the fans shouldnt just stay on.as the others have suggested they cut in quite soon once youve stopped,particularly if you have a long slow approach to stopping like i have where i live.once the fans cut in they should stay on for a minute or so then cut off.then on and off until stabilises around 90-93 if you wait long enough i find ,and they just continue to turn on and off.although this is on a griff 500,my chim 500 was the same,id expect similar for 400 also.

[deeen]

parrot of doom said:

Hmmm, my thermostat is about 80-85 while driving, and 90+ when stationary. Fans work ok though.

Sounds fine, within the normal variation for these cars I think. As I said, I don't start to get excited until my needle tickles the 100 mark.

[spend]

I think it would be prudent to get your temp gauge checked. It can flutter if the spade connector to the sender is 'tired'. Fans coming on could indicate that your gauge is under-reading. Personally I wouldnt bank on the gauge. If you cant get somebody to do it, Maplins sell the cheap IR thermometer for @£30 at the mo IIRC.

Dave

[chimburt]

erm. your car works. leave it alone!

the cooling system is a bit border-line, and you do have to keep an eye on it for changes in behaviour, so that you can pounce if anything goes pear-shaped before any damage is done.
the behaviour you describe is fine though. doesn't sound as though the gauge is flapping around to me - the fact that the temp is stable at idle is good, and although the fans stay on this is most likely due to a lower temp otter switch being fitted. if you had the regular one then it would probably cut in and out at around 90-85. i have always been happy for the fans to come in a bit earlier to be on the safe side, even if they do stay on until the traffic starts to move again.
if you are really worried about it you can re-wire the fans with extra relays from another supply - this will make them run a bit quicker ( the original supply system is 'on the edge' to say the least, in terms of current supply capability ), but you'd probably find it behaves exactly the same way.
if you are super-worried you can get a temp gauge as somebody else suggested and point it at things, but of course you won't be able to do that with the bonnet down......


don't worry until the needle hits 100+ or you get a sudden change in behaviour from it.

[j8 tro]

Dobi
I have an early (94) 400 and had concerns within my running temperature in the first few weeks of ownership. Firstly my temp gauge jumped around when I hit bumps and was traced back to a faulty spade fixing as spend mentioned (look under the bonnet in front of the 400 stamped cover. connected directly to the front) replace this and it should sort out the jumpy readings. Also note that the gauge and the actual fans kicking in are in no way connected.

I have also learnt that earlier Chims do run hotter for some reason. Mine runs about 80 degrees normally and my fans don’t kick in till well after 90. Due to a couple of 20 pence 50 pence moments I went to central TVR near me who had a quick look.
He said everything looked fine but my fans did kick in a bit hit and miss. On/off a couple of times before kicking in properly. I bought a new otter switch from them for about £12 which ill fit myself. (30mm socket under the bottom of the block, looks quite simple to do). Haven’t done mine yet but am assured by C-TVR the fans will kick in sooner.
Hope this helps

[M@H]

j8 tro said:

.... I bought a new otter switch from them for about £12 which ill fit myself. (30mm socket under the bottom of the block, looks quite simple to do).

Block !!!??

The Otter Switch is threaded into the bottom of the swirl pot, not the engine-block

Matt

[j8 tro]

My mistake........been a long day..........

[M@H]

No worries.. just checking

[spend]

Just noticed you said the tank is only 1/2 full. Is it a pre-serp with the 1 big expansion / swirl tank?

Anybody else with a pre-serp that only has 1/2 full swirl tank? Dont think I'd have any water in heater or heads if mine was that low. On mine normal is only about 50-60mm from the top - when filling pumping the air out by squeezing the rad hoses works fine for me.

[2 Smokin Barrels]

Nuggs said:

parrot of doom said: Hmmm, my thermostat is about 80-85 while driving, and 90+ when stationary. Fans work ok though. Parrot, IIRC the early Chims (i.e. non-Cerbera-style front) do tend to run a little hotter as not so much cool air gets through the front dam.

My experience has been the opposite. That is to say the newer cars show a higher temperature on the guage, particularly when stationary. (They may actually be cooled more efficiently by the later front end, but guages say the opposite)

[anonymous-user]

Thanks for all the replies. Mongoose is spot on, at standstill the fans wont kick in and out as he describes... my wedge used to turn the fans on/off almost rythmically (crap spelling!). I have also noticed from the bible that it dosnt have a shield fitted next to the otter switch, so if there has been a lower setting otter fitted plus its getting the heat straight of the exhaust this is probably why they dont cut of until I drive off and get better air flow through the car.

I must admit when you read all the threads it really helps. Cheers all.

I will have another play over the weekend.