Overheating temp ?

[Solitude]

My car has the fan wired direct to first stop on the key (comes on permanently when ignition is on)

Whilst driving she runs at around 70 deg up to around 90 deg (on the dial).

Stuck in traffic today, she crept up to over 100 and would have risen more unless i'd moved on (as fan is running already there is nothing else to "kick in")

I was wondering at what point i should become concerned and pull over !!

Any input chaps ?

Gavin

[jmorgan]

From experience, rad to be in tip top condition. No air locks, pressure caps tight and sealing cap on swan neck good and not leaking. Pipe work to the various bit at the top of the engine to be a simple as possible and feeds back to the expansion tank correct.

Off the top of me head.

Edit. My fan comes on with a switch not all the time. I never use the overide unless in traffic and can see the thermostat kick in and off on the temp gauge when giving it some. Still no fan .

I really really must wire it to the temp sensor, just on the overide at the moment.

Edit two. I filled the gaps around the rad to stream the air in. There are huge gaps around it if not looked after properly the air will spill around it. Bought a temp tell tale sticky and attached it to the top hose off the thermostat housing and found my guage is pretty bang on. Got a infra red temp reader and cheacke the go and return feeds for the temp difference.

Edited by jmorgan on Monday 25th April 15:40

[jeff m]

I don't have a 350 but due to lack of replies....

100...time for concern.
A car shouldn't run between 70 and 100.
It should reach its running temp and stay there.
A combination of things need to be right for this to happen.
Full coolant system with correct antifreeze %.
A working thermostat.
An unclogged rad, decent fan that operates at correct temp. (It should maintain optimum engine temp.)

Possible solutions.
Check radiater cowling is complete and not removed by prev owner who thought it wasn't needed.
Flush coolant system (including heater)
New thermostat.
Don't stop at red lights

ETA if it is a aftermarket fan check the blades are installed correctly. It is possible to have a fan blowing in the right direction even with the "cupping" of the blade in the wrong direction.

Edited by jeff m on Monday 25th April 15:40

[Tasmindevil]

Possibly 110-115, running around 85 is a good temp but some run lower and depends on your thermostat, mine drops to 70 as well but I will be going for a different thermostat as I would prefer to be up in the mid 80's on the open road. I also have belt and braces with the fan (Twin fans), runs off the otter but I have a back up switch as well.

[jmorgan]

Got this knocking around. Usual disclaimer for its use. Mine is different

[KelWedge]

Much over 100 is worry time, I saw 120 (once) on mine, on the old engine

[adam quantrill]

110 is time to worry but when the fan kicks in it should come down to 90.

I don't think it should boil until over 118C with a decent radiator cap.

The question is - how accurate is your temperature gauge?

[dixiebabes]

Mine boiled over ages ago at 110 but as adam says how accurate is the gauge?

dix

[Solitude]

Thank you chaps.
I have no idea how good the gauge is and no idea apart from opening up while hot and shoving a thermometer down her throat !!

The fact that (whilst in traffic) she climbs, leads me to believe she works (accurate or not) and that if my fan is running constantly, then sooner or later she will boil.

I will get panned for this but hey.....what is the cap on the swan neck for? I have topped her up via the bottle, is that correct ? Where is the stat...(top of the rad i suppose) and how hard is it (stat, rad et-al) to get it all out and check/flush and carry out remedial workS

I appear to have no leaks, but am in mind to replace pipework as she sat for eight years, and like the bushes, i should imagine they are in self destruct mode !!

I am handy with the tools and un-afraid of dirt, but lack the experience so bear with me lads.

Thank you for all your replies and on-going help and support, and feel free to ask any electrical (domestic or commercial) advice from me in return

Gavin

[Mr Tank]

Hi Gavin

Early 350i!
How early as the water pipe work on the real early cars did cause some problems (Hence the reason for the change)

Also the most common cause I have found on the early cars was the cap on the plastic header tank, it let's water out if it's poorly fitting/worn, down the overfil pipe to the floor! On later cars that's not a problem as the water goes into another tank, which is then sucked back when it cools down!

Andy

[adam quantrill]

Do the test then - you should do this when buying a car:

a) go for a drive to warm up
b) get back and park, leave the engine running
c) observe the fan cuts in at 95-100 ish.
d) rpm shoud be 650 or over when fan cuts in
e) observe that temperature comes down to 90 (ish), fan turns off
f) this cycle should repeat

Check for leaks at the same time, or dumping of coolant out of the overflow.

[Solitude]

Mr Tank said:

Hi Gavin

Early 350i!
How early as the water pipe work on the real early cars did cause some problems (Hence the reason for the change)

Also the most common cause I have found on the early cars was the cap on the plastic header tank, it let's water out if it's poorly fitting/worn, down the overfil pipe to the floor! On later cars that's not a problem as the water goes into another tank, which is then sucked back when it cools down!

Andy

Hi Andy,
Chassis number 5554 if that means anything, (must check the photo's of the factory chalk board i submitted !!) she was registered 19th october 1983

And does not have the "second tank"

I don't think she is losing water mind you.....but stuck in the traffic, i was becoming nervous at the rise in temp.
Thought that the fans would (constantly running) keep her cool !!

Gavin

[dixiebabes]

I hear you Gavin im like that all the time, soon as it goes over 90 i keep getting told off from the missus for taking less than the usual little notice of her!

Dix

[GV]

The best way to test your gauge is to get an infra red heat sensor - quite cheap from the 'bay - fire its laser at your thermo housing and then the temp sesnor and you will get an accurate reading. My gauge was only a couple of degrees out when tested.

Provided you have tight connections, good seals on your pressure caps and a properly bled rad with no air locks you should have a steady temp. You also need to accept that our cars always run hot too

[Jonny weggie]

Gavin,

Your lucky you havent blew your fuse or overheated the relay with the fan being on all the time,my car runs when warm at 84 degrees and in town 90 degrees [sometimes] but fans come on at 86 deg would be to your advantage if things were changed around.

jonny.

[Mr Tank]

Solitude said:

Hi Andy,
Chassis number 5554 if that means anything, (must check the photo's of the factory chalk board i submitted !!) she was registered 19th october 1983

Gavin

Gavin

5544 means she is an early MK 1 350i they do have a differant cooling layout to later cars, apart from lack of the secound tank the bottom hose out of the header tank goes into the heater system not strait into the engine system. I intially had cooling problems with no 1 and found it was losing water out the over flow on the move but didn't when I was parked unles I revered it up high! I changed the tank and cap, problem solved.

Andy

[wedgeinald]

Mine (280) used to "overheat" gauge now tops out at 210F (sorry no C on my gague! but about 85C) Found recently that running it on SUPER unleaded dropped the "average" temp down by 10-20F, I now plan to use ONLY super unleaded fuel. The engine was setup using standard unleaded and runs perfectly well on unleaded, but its obvious now it still prefers the higher octane fuel.

I used to have "only" an elecrtic fan and that was fine but struggled in REALLY hot weather (especially at Classic Le Mans last year when ambient was 40C) putting the "viscous" fan back on and keeping the electric for really hot times has improved things no end (I feel like i could take the electric fan off, but I wont!) the fan is on an overide switch.

I'm considering a rad flush and see if that helps drop the average temp a little more in cooler weather.

Hope some of this is of help...

Norman

[honestjohntoo]

This thread raises some interesting fundamental issues.

wedgeinald said:

putting the "viscous" fan back on and keeping the electric for really hot times has improved things no end (I feel like i could take the electric fan off, but I wont!) the fan is on an overide switch.

Without doubt the way to go! The most misunderstood component in the RV8 (or any other engine) cooling system. It is so clever it puts most owners who choose to remove it at a severe disadvantage.

The underlying requirement for any successful cooling system is STABILITY, and it is the function of a correctly working Viscous fan coupling that guarantees that requirement.

Sure! Other components and good coolant flow have to play their part, but the Viscous Fan Coupling is the only ACTIVE (original) component in play when the engine is at working temperature, in that it employs classic "negative feedback" principles - responding instantly and subtly to any minor changes in the heat being extracted from the coolant by the radiator.

Any change in temperature in that cosy space immediately behind the radiator is instantly detected by the unit's temperature sensitive control valve and the fan speed changes to suit the new heat load. Up or Down, it matters not! The Viscous Fan Coupling will adjust the cooling effect to exactly what is needed to maintain stability of engine temperature.

wedgeinald said:

I'm considering a rad flush and see if that helps drop the average temp a little more in cooler weather.

It's axiomatic, that partially blocked coolant galleries will restrict coolant flow, sometimes so badly that the really hot spots inside the water jacketed engine adjacent to the exhaust valves/manifold will actually cause the coolant thereabouts to bubble into steam, despite the coolant boiling point being raised to 135 deg C at 15 psi - and that steam now seriously threatens to expand rapidly and push coolant out of the system via the expansion tank pressure cap. We have all been there!

And once that happens, no amount of correct function by the Viscous Fan Coupling or other components, can keep things stable. The evidence is seen on the wildly fluctuating engine temperature gauge, similar in many ways to the same effect seen when air locks in the system have not been eliminated.

Flushing and reverse flushing the whole of the cooling system should be a routine biennial task along with several others.

This whole subject of Cooling System Stability is discussed here

Now you are really cooking!

[Wedg1e]

Makes you wonder why the world's manufacturers don't still fit thermostatic fans, since they're that wonderful
Along with drum brakes, single-choke carburettors and 3-speed gearboxes. Oh, and leather friction dampers. To say nothing of acetylene lamps and hand-cranks.

I bet a pound to a pinch of poo that an electronic sensor (a.k.a. K-type thermocouple) can respond more instantly than a lump of wax in a fan boss. Also modern fan design means that blades are more efficient at drawing air, quieter and waste less time stirring up the engine bay. Oh, and they don't sap mechanical energy from the engine (however miniscule an amount it may be).

Still if it works for our man, it can't be all bad...

[jmorgan]

We had to bin out landrover 110 viscous fan but we were dragging a horse box sized trailer loaded with goodies up mountains. Needed the airflow going a lot sooner. Also helped in traffic.


OK, I know, different use etc.