I think i may know the answer.

[series111]

Hi to all you good people

As I have said in the heading I think I know what you going to say.

A couple of months ago I fitted a revtec electric 12" fan recored radiator 82 degree thermostat and 13 lb radiator cap to my dolomite sprint, since doing this I have noticed that driving around town at low speeds the temp is half way on the gauge, when driving at speed or going up hill the temp rises to three quarters on the gauge then falls back to half way again.

The system seems to be full with no air locks and the heater works ok, the fan cuts in and out and works ok, I have a revtec adjustable sensor cut into the top hose.

When it was running on the fan belt driven fan it would go up to halfway and stay there what ever, it only started over heating since fitting the electric fan

There does not seem to be any air bubbles rising into the expansion tank, there is a water stain coming from the head under the inlet mamifold which seems to have dried up since I retorqued the head down.

Would it be the head gasket or could it be something else.

[cliftyhanger]

Those symptoms are typical of a radiator not being able to cool enough.
To nail it down, remove the electric fan ad refit the original. If it still gets warmer at speed, the rad is not good enough. If problem solved, leave it alone.

[xvivalve]

The standard Sprint fan is 14" in diameter which is also the approximate height of the radiator.

14" gives a swept area of 41 square inches greater than a 12" fan.

I suspect Clive's suggestion will resolve your problem, so no, I don't think it's the head gasket, but it may well be if you continue!

[MIG Wielder]

I suppose the new fan is "sucking " not "blowing " ?
Tony.

[tamtrucks]

is the water pump any good? just a thought as its not mentioned

[Carledo]

I'm with Clive, sounds like an under-performing rad to me too.

I normally associate this with a rad that has a partial blockage, but there has been a tendency by a few "specialist" rad firms (who should know better) over the last few years to recore Sprint rads with the easier to source and slightly cheaper 1850 core - and it's just not quite good enough, especially higher in the rev range or when working hard.

I know there's a difference in the core count, IIRC the 1850 has 24 cores and the Sprint is 28, (no doubt Alun or somene will correct me if i'm wrong) There also is (or was) an uprated close pack core for Sprint which may still be available, though I haven't bought one in a good few years now.

A car fitted with an electric fan will exhibit a lot of temperature fluctuation on the guage that an engine driven fan car won't and this can cause some hysteria among Sprint drivers who drive with one eye on the temp guage at all times and respond badly to a fraction of a mm movement in the needle. This CAN take a bit of adapting to!

HOWEVER, any Sprint SHOULD be able to run at a CONSTANT temp (actual temp shown can vary dependent on a myriad of other factors) despite hills or revs or ambient temp (at least up to around 35 degrees C) so long as air is passing through the rad. If it doesn't and temp shown is load dependent WHILST DRIVING, it's a rad problem.

Steve

[soe8m]

Currently I'm driving someone elses project (don't start) that did overheat at the start when going to drive it. No thermostat fitted and a faulty pressure cap were the cause.

The car didn't had the original fan but a kenlowe electric fitted with about 50 brackets, 120 tiewraps and about 10cm from the core. No shroud ofcourse with these things.

I replaced the kenlowe by a decent Derale fan, the best there are and what does make a revotec thing or similar look like toy's.

That was last summer. I didn't wired the fan in yet as the car needed more wiring later and the plan was all at once.

I do drive that car daily for a year without any fan and that goes fine with a healthy engine. At normal traffic a fan isn't needed and when at idle for a traffic light when the temp rises on a hot day putting the heater on is enough to keep it in limits.


In other words, your electric fan isn't the problem. Do you have the correct type of thermostat fitted? A lot have a single type fitted and then trying to cure some overheating. A dual valve is needed.

Do you have enough coolant in the engine? New pressurecaps aren't that accurate and spill your coolant so after some miles and not checking yet it can be loo low. It's easy to temporary T-in a pressure gauge and (bicycle tire) pump to see at what pressure the cap does open. The average garage workshop should have one also to check cooling systems for leaks. Then you are sure seeing it open at 13. Buying just a new one doesn't say anything.

A few simple things can cause major issues and most of the time it's a simple wrong part or a faulty new aftermarket part.

Jeroen

[tangocharlie1]

i'm confused why did you go to the trouble of changing to a an electric fan/radiator if it was working perfectly well with the standard set up?

[Richard the old one]

Having recently had a problem where the pressure cap on one of my cars stuck and caused the system to overpressure with the result that the water pump started to leak, I decided to check the operating pressures on the four 1500HLs that I run and a new spare cap that I have purchased from Rimmers.

I did this using a tyre inflator and a spare water expansion bottle see photograph of the set up that I used. Actually It would be quite simple to do the test on the car by just disconnecting the hose from the top of the radiator and connecting the inflator to the hose. The readings I obtained were 14.5, 14, 13, 13 and 10. The two that vented at 13 were actually new recently from Rimmers. The results raise the question.

What affect will the slightly higher and lower pressures have and should I change them as I have not noticed any problems.

[series111]

Thank you for all your answers, yes it is a sucker fan, and yes it is the right thermostat, what I will have to do is put the old one on and give that a try.

Will it do any harm running like this, as Steve says with a electric fan the temp will go up and down?

[sprint95m]

i'm confused why did you go to the trouble of changing to a an electric fan/radiator if it was working perfectly well with the standard set up?

That is an interesting question, so I shall comment if I may.


When I ran my first Sprint through the nineties I did so with a standard set up and
encountered no problems whatsoever.

However, for my current (second) Sprint I am going for an electric fan
mainly because the viscous coupling could fail resulting in the fan destroying the radiator
but also because there is a small efficiency gain by not driving a the belt driven fan all the time.

On my 1850 I did fit a Saab radiator as an experiment, but other than being much cheaper
I concluded this offers no real advantage over the standard radiator.
At first I did run without a fan and it didn’t seem inclined to overheat and then when I fitted an electric fan
I don’t think it ever came on (it was really quiet even with the bonnet opened. Can’t remember the make
but it was marked made in Italy.) I did then fit a warning light to come on when it was running just to confirm..


Maybe not a big concern, but a belt driven fan makes a lot of noise
causing wild life to vacate the road readily.
You can get a (silent to us) whistle instead…….



Ian

[soe8m]

And on a dynojet with or without an original fan there's a difference of 4 hp at the wheels. An electric fan will give a much lower fuel consumption.

Jeroen

[Carledo]

If it USED to run bang on normal then we can assume the guage is not faulty and it's readings can be trusted. It's not unknown for a sender to give a false high reading when there is nothing actually wrong with the car, but this is probably NOT the case with yours.

In which case, I would say that so long as it doesn't go OVER 3/4 without the fan coming in and bringing the temp down again, you are probably safe to drive it.

HOWEVER, this business of it getting overly warm when driving at higher road speeds or under load (like climbing hills) does need investigating.

As a preliminary, i'd be counting the number of horizontal tubes in the rad core and also making sure it has 3 rows of tubes, i've seen all manner of things done to radiators over the years and take nothing for granted! If I can find a proper OE Sprint rad round here, i'll do a tube count and confirm the numbers.

Steve

[Bumpa]

This topic is discussed endlessly on the MGB V8 sites I read. The question that needs to be asked is "Is it overheating or is it just hot?". My MGB V8 seems to need it's twin fans almost permanently at town speeds in warm weather, but it's not overheating in that it suffers no harm and loses no coolant.

Stuck in traffic in France with the shade temp at 37 C with the fans running, the V8's temp gauge (calibrated in Fahrenheit) reached 230 degrees (top of the scale) and then started to enter the oil pressure gauge zone on those dual gauges that MG use. My wife and I were overheating for sure, but the engine was fine. The fuel injection made sure it didn't stumble or run rough and it lost no coolant. I don't consider it overheated, it just got hot!

It sounds like your electric fan isn't as efficient as the viscous fan, but I don't consider it to have overheated.

[Carledo]

This topic is discussed endlessly on the MGB V8 sites I read.

It sounds like your electric fan isn't as efficient as the viscous fan, but I don't consider it to have overheated.

The thing is, that any engine driven viscous fan does nothing at all over 5mph! Once you are moving, the passage of cold(er) air through the rad takes over the chore of cooling. The same should be true with an electric fan. You should really only have the fan deploy when in stationary or near stationary traffic, if it's coming in while on the move, then the engine is undercooled, simple as!

My Dolomega, with it's 2.2 Vauxhall engine and Saab rad with a 12" pusher fan is a proper mongrel, but it cools properly. even on a hot day (like a couple of weeks ago at the Gaydon show) it runs uphill and down dale at motorway speeds and the guage needle never budges from its "normal" value which is about 3/8 up the guage. However, sit in traffic for 5 mins and the guage shoots up to just over 5/8 and the fan deploys. Get rolling again and it's back to 3/8 in a couple of minutes. In winter, it hardly ever gets hot enough for the fan to cut in. This engine has a 92 degree thermostat and the guage is a mishmash of parts with a Triumph guage and a Vauxhall sender. I have no idea what precise temperature "normal" is and I don't need to. I suspect if it read true, "normal" would be at 3/4 and the fan would come in just short of the red bit! Which would be just the same really but give me kittens anyway, so i'll leave well alone!

The MGBGT with V8 fitted is a bit of a special case, it's a very cramped fit in the engine bay, so not much room for airflow round the block, there's not much room for the giant rad that engine seems to prefer (they ALWAYS seem to run hot, even in cars that were built for them) and lastly the car has a very low frontal area with a concomitant small and shallow grille, which doesn't help when driving, especially in high ambients. Were it my car, i'd have (as the Dolomega has) some extra holes for cold air in the valance, under the bumper and also a big batch of louvres in the bonnet to help get the hot air out again!

Steve