Undercooling Overheating
Turbo Mini Forums

My problem has been over cooling when moving and overheating when stopped.

Overheating.
As soon as there is no air flow under the bonnet the temperature starts to rise rapidly. As soon as the engine speed rises and the the car is moving again the temperature starts to drop.
I fitted a fan under the wing that cuts in automatically at about 90 degrees. It worked very well. It slowed the temperature rise down but it didn't stop it. Fortunately I didn't get stuck in heavy traffic jams during the summer so it was OK.

I thought if I fitted the electric fan to the radiator between the rad and the wing it would pull more air directly through the radiator so stopping the temperature rise when stopped. The fan I have is to deep to fit without wing mods.

Over cooling.
I restored the car and kept it as the original ERA. It has an auxiliary radiator and an oil cooler with no thermostat. The main radiator I fitted a Minispares 2 core rad. All to increase the cooling. And it does. When the car is moving the water temperature reads about 80 degrees and the oil temperature doesn't get above 60 degrees and takes a long time to get to that. When stopped the oil temp starts to rise but doesn't get to very high before the water temp gets too a worrying level.

I thought I should fit a thermostat on the oil cooler to stop the extra cooling of the oil. What I don't want to do is cause a bigger problem with the overheating.
Any suggestions?
Is there an electric fan that fits between the wing and the radiator that doesn't need the inner wing to be cut?

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Edited by ERA1028 on 3rd Jan, 2015.

a quick answer......... do you have a 74 deg stat fitted ? and what size water pump pully do you have on a large one or small ? my guess is it a larger type, anyway tis is just a start for more questions and and answers

It is a large pump pulley and an 88 degree themostat

What condition is the pump in? could it be not pumping enough at idle, but with all your cooling mods, more than enough at speed?

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A small pump pulley would be a good help

the "large" pulley slows the pump and fan speed vs the stock pulley large ones are mostly on high rpm/speed cars (stop start traffic ull want the small one)

has it been fine then it started getting hot at idle or has this always been since it was built or bought?

also what kind of pump? the pressed steel ones imo are not much chop i lean towards the cast ones that have better impeller to case clearance the tighter that gap the more efficient the pump more pressure in the block and head (if the pressure goes up the boiling point goes up ie less chance of air being caught up)

air lock? rusty block/head clogged rad?

are the fueling and ignition good?

a cheep way to get the oil temp up is to just block the air flow to a few rows of fins trail and error but with a gauge not that hard to sort the max temp out

The water pump is a new cast impeller type.
It has always run like this from the rebuild.
The block and head are clear. It has only done about 1500 miles since rebuild.
The fuelling and timing are fine. The car goes great.
I have a smaller pulley that I am going to fit and I thought I would fit a metal 4 blade fan instead of the multi blade plastic one. I also thought to remove the oil cooler and pipe the filter up as standard just to give me an idea how much cooling it is responsible for. My worry is changing things to reduce the cooling and causing problems at the other end of the scale. I think I really need an electric fan as close to the rad as possible. But am reluctant to cut the bodywork.

stupid q era , i'm sure you have thought of, but is the electrical fan blowing the right way ?

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60 degrees is way too cool for the oil. Should be around 90-100 degrees.

Robert had a good point about the fan. I'd also check the pump. Some of the new ones have too much clearance between the impeller and housing.

How well set up is the car as well? Timing and fuelling could have an impact on temps, although i think that is more likely to be at the higher revs (I'm sure someone more technical than me can correct,)

The mechanical fan and the electric fan I fitted are working the right way round. How much is too much clearance at the impeller. I had it R/R at TMS in Knaresborough and it was fine. The guy there did a god job. As I mentioned when I increase the revs the temperature stops rising and can start to drop. I suppose this points to the larger pulley I have on. Putting the smaller one on will increase the pump speed. Anyone any idea the increase in rpm between the two 3.875 and 4.75. Is the Minispares high capacity pump GWP134EVO worth considering? But wont this increase the cooling while moving? The problem I want to stop also. My head is starting to hurt!

yes the smaller pully and HC pump is the way to start, take it from there and you head wont hurt ......lol

if you didn't know those metal fans are fairly noisy

are the HC pumps actually any different? or is it the cast type they simply call a HC vs the pressed steel ones?

no point buying a HC one if its just the cast type like you all ready have worth a check

the actual rpm the pump sees will be dependent on the crank pully size aswell as the pump measure that and take the ratio and multiply it this works for alternator aswell

all the minis ive seen should have some stamped triangle tabs on the rad cowl (the part spot welded to the car) to hold such strip sealing the hot side of the rad to the body making the hot air go out of the bay not recirculate

you have got the fan cowl on just to check?

On 3rd Jan, 2015 ERA1028 said:
before the water temp gets too a worrying level.

Is there an electric fan that fits between the wing and the radiator that doesn't need the inner wing to be cut?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

In my attempts to stop the overheating I fitted a fan under the wing as in the picture in my first post. It slowed the increase down a lot it worked very well but the temperature still rose. A lot slower but it still rose. I thought if I fitted one closer to the rad in the space between the rad and the inner wing it would pull more air through the rad. I made a shroud to go around the rad to close the gap.

All looks good, really that should have a good ability to keep things cool.

Are you sure things like ignition timing and fueling are good at idle etc ?

Cant recall what radiator I had back then, but it was an uprated one of some sort.might have been a 3/4 core kind of thing.
But I'm sure there must be far far more efficient cores available today

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I'll chip in and say that there is something simple wrong here but its difficult to pinpoint what it might be as i dont have half the information i would want to make reasonable suggestion.

I would want to know the exact pluming circuit especially with the extra rad. However, there are plenty minis without this extra rad that dont overheat. Also on the same point, the temp should not drop much below the thermostat temp, which again might point at the extra rad as being the culpret since it has no thermostat.

If you dont want to remove the extra rad to see if it makes a difference ( all be it as i said earlier that many dont have one) you could try a 6mm retrictor in one of the hoses that feeds it.

Edited by Sprocket on 3rd Jan, 2015.

It is piped from the bottom of the main radiator to the aux radiator to a sandwich plate on the head below the thermostat and the top hose.

As Sprocket says, it's strange you should even need an additional rad.

If we seen extreme temps in the UK I could maybe understand this, but for most of the time it shouldnt be needed.

Is your heater plumbing normal ? If anything and you wanted better engine cooling. I'd sooner have taken the heater takeoff near the coil, plumbed it through an additional rad and then returned to the bottom hose or bottom of rad.

The takeoff at the stat I'd sooner use it for your heater. That should promote better water flow through the block/head from a cooling perspective.

Of course on the other hand, when sitting still...your additional rad will be doing nothing other than re-circulating hot water back into the water pump that has not been cooled. So it could very easily be a cause of heating, rather than what you hoped as cooling.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

It's difficult to tell from that photo (really need a close-up of it) but could the mechanical fan be on backwards ?

They can be fitted either way around and, although the genuine ones are marked "engine side" I've seen copies that aren't.

If fitted backwards they still blow in the correct direction - because the angle of the blade relative to the airflow is the same whichever way around they are - but the blades themselves are a curved aerofoil shape (like an aircraft wing) so are much more efficient if the leading edge is hitting the air, not the trailing edge.

That could explain poor performance when the fan is turning slowly.

One other thought, is the spacer fitted ?

There seems a lot of blade in view outside the cowl.

Schrödinger's cat - so which one am I ???

Try blocking the extra rad as an experiment, perhaps (depending how its plumbed) its introducing cool enough water to shut the stat at even tho the engine is getting toasty. If it flows to return in the wrong place.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

I think due to the way the auxiliary radiator is plumbed in there is too much coolent flow through the auxiliary radiator thus causing the temp to drop when driving and to heat when stopped(no air flow through the aux rad). Block the auxiliary and check if the temp behaves in the same way.

The way the aux rad is plumbed in is as the original cars came from ERA so could be classed as standard. Because I have fitted a very efficient main rad that wasn't available in 1989 when the original was built I suspect that I have overdone it hence the to cool running. This is two problems I have to solve to bring the running temp up while keeping the standing temp normal. Some good suggestions so far some that confirm my own thoughts about the problem. ERA also used the turbo head with better cooling. The water galleries were bigger as you know. When I rebuilt the engine I used an MED turbo head. They didn't want the original turbo head because they said that it was difficult to machine as they could cut through to the water gallery so I supplied them with a standard 1275 head to work. I cant see that it would make a difference but it is a change from original.
There is a spacer fitted at the fan I think it is the camera angle but I will check it when I put it back together. The concave side of the blade is facing the rad. I could have it wrong.

Edited by ERA1028 on 4th Jan, 2015.

Remove or at least clamp up a hose to the additional rad. It shouldnt be needed and is no doubt part of the overall problem.

Head, unlikely to be the problem.

Are you using the normal water pump bypass, or is it blocked off ?

If you really had to retain the additional rad, I would block off that bypass.

But fit smallest pump pulley
Clamp off water flow through additional rad
ensure blower fan is fitted correctly.
ensure your electric fan is a puller and with the blades correct rotation

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will