Cooling

[cdt]

What temperature should the fans kick in at? Mine don't seem to kick in until about half way into the red on the water temperature guage - about 110 degrees.

Also when driving the water temperature will suddenly seem to go up, without any change in driving speed. So if I'm travelling at a constant speed of 70mph, the temperature will suddenly go up from just below the bar to well into the red and back down when the fans kick in. It isn't a problem as the fans always kick in. Just that I'd have thought the air traveling through the radiator should cool it down.

Any ideas, could the airflow through the radiator be blocked? Going to try putting some water wetter in the radiator.

[badredwedge]

The fan should kick in at about 88-90 deg, thats assuming that you guage is correct. As for a sudden rise maybe short of water or an airlock ?? Let us know how you get on with wetter water, I have been thinking about getting some.

[matt-man]

Water wetter is pretty good from me and my dads experiance in the ultima.

We had a few minor issues with the car getting hot when in traffic at Lemans the first year we took her, so did lots to stop it happening again including an Oil cooler with a big fan, water wetter, extra fans in th engine bay and all sorts...did the job so i guess the water wetter helps!

As tescos say, every little helps...

[cdt]

badredwedge said:

The fan should kick in at about 88-90 deg, thats assuming that you guage is correct. As for a sudden rise maybe short of water or an airlock ?? Let us know how you get on with wetter water, I have been thinking about getting some.

Coolant level looks okay, how can I tell if I have an airlock and how do I get rid of it?

[GreenV8S]

Either the gauge is lying, or you have a cooling system problem which could damage the engine if left. It's really bad for the engine to have the temperature go up and down like that and you want to get that fixed if it really is happening. But there's a chance it is just an electrical problem with the gauge, so don't get the petrol and matches out just yet.

[silverback mike]

Mine comes in at spot on 100. Always been the same apparently....

[leorest]

cdt said:

Coolant level looks okay, how can I tell if I have an airlock and how do I get rid of it?

I've always had success with parking on a slope (or sitting the front on stands) and running the car up to temp with the swan neck cap off and keeping it brimmed. Heater obviously needs to be full on. Some have fitted a bleed point for the heater which may help but I've got by without this. When I first got the car I flushed the system for ages in both directions, using mains pressure, till crystal clear water came out. Since then cooling has never been a problem.

[leorest]

cdt said:

...the temperature will suddenly go up from just below the bar to well into the red and back down when the fans kick in. It isn't a problem as the fans always kick in.

As the fans seem to follow the gauge I think it's unlikely to be electrical as the circuits are quite separate. As Mr V8S says best to get it checked out. My money would be on an airlock but that's only because I can't think of anything else which would cause a sudden rise in coolant temperature.

[matt-man]

I do sometimes find that whilst my car is warming up and im driving, until the temp is getting right up and the thermostat opens the temp stays at about 80 and jumps up to the red but quite quickly then settling again to about 80 where it stays for the rest of the journey!

Sounds similar...does it do this in traffic to? You could always change the thermostat so that it comes in earlier? Its definatly better to be safe than sorry...i think!

[cdt]

leorest said:

cdt said: ...the temperature will suddenly go up from just below the bar to well into the red and back down when the fans kick in. It isn't a problem as the fans always kick in. As the fans seem to follow the gauge I think it's unlikely to be electrical as the circuits are quite separate. As Mr V8S says best to get it checked out. My money would be on an airlock but that's only because I can't think of anything else which would cause a sudden rise in coolant temperature.

I must double check the fans come in to reduce the temperature (hard to tell at speed), fairly sure though.

[cdt]

leorest said:

I've always had success with parking on a slope (or sitting the front on stands) and running the car up to temp with the swan neck cap off and keeping it brimmed. Heater obviously needs to be full on. Some have fitted a bleed point for the heater which may help but I've got by without this.

Does this need to be started with the engine/radiator cold? Can you clarify what you mean by 'keeping it brimmed'.

How easy is it to flush the system? Is it all described in the wedge bible?

Thanks.

[Jon S]

When I first got my 350 i the temperature gauge sometimes went up and back down again for no reason, just during normal driving.

I used to check the coolant level at the expansion tank, but through these threads read it should be checked at the swan neck filler. Sure enough when I checked it there, the level was a bit low. So left it running for a while with the cap off and topped it up and since then it runs slightly cooler and the gauge doesnt seem to go up and down anymore. Must have got rid of an airlock when I topped up the system properly.

[jmorgan]

Best thing I did was to fit the heater system bleed valve.

As for the various methods, I tried the official way, the unofficial way, jacks and all sorts. None of them hit it on the head in one go and I have a steep drive. Bit of them all in my circumstances but a lot easier since the valve. Next idea is a an easy access valve or a suitable hole on the corner of the rad away from the top hose side.

[dickymint]

Looks like the AJP engines had similar problems?
http://cgi.ebay.co.uk/TVR-CERBERA-V8-

[cdt]

When checked at the swan neck what should the correct level be?

[dickymint]

Right up to the brim - it helps to squish the rubber hose a lot to release more air.

[jmorgan]

Don't know how relevant this bit is. I was getting a few issues with an airlock after I thought I had bled it OK. The top of my expansion tank appeared to be as low as or lower than the pipes feeding my heater matrix. So the air in a cold system expansion tank used to go for a wander around the engine. Lifted the tank and altered a bleed pipe and it seemed to behave a bit more. Still not perfect on some days.

[leorest]

cdt said:

Does this need to be started with the engine/radiator cold? Can you clarify what you mean by 'keeping it brimmed'. How easy is it to flush the system? Is it all described in the wedge bible? Thanks.

By flushing I mean disconnect a coolant pipe and clamp a garden hose in one side and run mains water pressure for a while then move the hose to the other side and flush again. This has now flushed in both directions. You can do this in a few places like top and bottom hoses and heater matrix. When doing the radiator it's wise to disconnect both ends so that you don't push all the crud out of the rad and into the block! It helps if there's no hosepipe ban and you are not on a water meter as you do use quite a few gallons!
'keeping it brimmed'= any time a gulp of air comes out the top put more coolant mixture in until no more goes in (eg stop adding more when your feet get wet)
Always start from cold as opening the swan neck when it's under pressure can be quite.... interesting. As it warms up you will see the level go down when the thermostat opens and also go up as the water expands. If a bit of water comes out don't worry just keep going until air bubbles stop coming out. As already said squeezing some of the hoses can help. It certainly gives you the feeling that you are doing some good. If your hoses are less than perfect the constant squeezing will damage them but in that case you're better off finding this out in your garage rather than in traffic on the way to Le Mans.
I'd say it's pretty easy flushing the system so long as you don't mind getting a bit wet.
One last thing. Keep an eye on the temperature while you do this just in case things go sky high!
Hope that helps some,
Leo

[TwoRobs]

Have had a 1986 350i for 3 years and when driving at speed the temperature always rose from 80 into the red, dropped to 80 and minutes later back to the red, etc, etc. Although the coolant needed topping up every 100 or so miles never had a problem. Searched and found a thread from Digga951 on 3rd December and realised that I incorrectly had two pressure caps. Replaced the cap on the swan neck with a blank cap. Pleased to say that the temperature is now a steady 80 at motorway speeds and hopefully the top up problem has also been solved.

[cdt]

Tried the topping up on a slope and its removed the air, coupled with the water wetter the temp stays below the line on the guage almost all of the time now.

Thanks for the help.