12 replies to this topic

[mullet]

Hi Community.

 

I know there are several threads on overheating, but yet to find a solution to my one so I am creating a new one, but to include what I think is an important symptom.

 

The car overheats very quickly, even if cruising around 40 - 50mph (as opposed slow traffic).  It gets so bad, it can even stall and takes 15 minutes' rest just to run again. 

 

I try taking some heat from the engine by turning on the internal heater.  That's when I noticed no heat is drawn from the engine into the internal heater if I am below 30mph.  The temperature gauge incorrectly reads a lower temperature if below about 30mph, too.  It's as if speed it triggering some higher pressure/better flow of radiator fluid around the engine and then the temperature gauge works better with this higher speed.  Radiator fluid level looks good and was changed a couple of years ago (and driven very little since then).

 

I feel the symptom is very much related to this problem.  What could cause the overheating, if the symptom itself is relevant?

[alpder]

Did you check the water pump still has all its impeller?

 

And if it's not that, a bit more about the car will help others: age and history, engine, things you've already tried, and when did it last work... that kind of stuff all helps narrow it down.

[mullet]

Hi Alpder.  Thanks for your reply.  A 1984 mayfair, automatic 1000cc.  I haven't tried anything yet and in fact it has always had a heating problem since I bought it 7 years ago, but seems worse now.  I think the timing might be slightly off, but I can't even drive it far enough to the garage that does actually work on minis as a speciality to get timing finely tuned (I struggle without tools, time or experience in this respect).

 

That said, I don't think it is caused by the timing being potentially off a little as it has been off before without such a heating issue.  This heating issue suddenly got a lot worse, so maybe some components suddently broke(?).

 

I see these pumps seem to be around 20 quid.  It doesn't seem a huge expense and I am capable of changing like-for-like.  Could it be worth simply replacing the unit and see if it changes anything?

[alpder]

Sorry, thought you'd already been through the usual suspects. My mistake.

 

No heat at the heater, and rapidly overheating, suggests a water flow problem(s). They could be separate issues - the heater valve and matrix are both known to clog up and prevent heat at the heater, while the overheating engine could possibly be something else. But start by looking for a single cause (Occam and all that.)

 

The threads you've already seen will highlight the most common causes - lack of water, stuck thermostat, blocked hose, collapsed hose, accumulation of crud in the system due to lack of regular flushing, massively excessive concentration of anti-freeze/water mix, slipping belt, excessively advanced timing, excessively lean mixture... right down to a mis-matched gauge/sensor causing it to over-read... others will add to that list for sure. Check those things first. Pump impeller failure is what you have a look at when everything else is ruled out.

[bpirie1000]

When the internal heat is selected do the hoses through the bulkhead get hot at all!

1984 mini would have the floating valve suspect that is where your issue may be..

They are renowned for being issues. Check the hoses either side when car is hot.

If pipe hot on one side then not on the other... bingo....

I would flush the internal heater matrix.

Also is the water a decent colour or roosts red?

****I stand corrected. The valve is on the left hand side of the head. *****

Edited by bpirie1000, 30 December 2024 - 04:07 PM.

[Designer]

Hi,

 

I don't think a 1984 has the floating valve, our 1988 Designer has the Heater Valve at the rear of the cylinder head furthest point from the thermostat housing.

We had the problem of the pipe from the valve to the matrix getting slightly warm but no heat in the return from the matrix to the bottom hose. Stripped it all down,

checked that the hoses had not collapsed internally, back flushed the matrix and heater now working. I would point out that we did not have any over heating.

Most of the time the needle is just below the blue line and occasionally goes just above if in heavy traffic and on very hot days.

 

Paddy

Edited by Designer, 30 December 2024 - 03:59 PM.

[mab01uk]

I would replace the water pump, impeller failure can and does happen with both the early small cast metal impeller and the later plastic impellers which means lack of circulation but no visible leaks. Even without the heater matrix valve open for heat the engine should not overheat, although having the heater and blower fan set to on, certainly does help give extra cooling when stuck in modern traffic jams on a warm summers day!

Replacing the pump is also a good opportunity to flush the cooling system and check all the hoses, etc.

Use a good quality replacement pump from Minispares as there are some cheap poor quality 'unbranded' ones on the market which either leak in the short term, suffer bearing failure or have a poor quality plastic impeller that melts, distorts or eventually just spins on its shaft....

Edited by mab01uk, 30 December 2024 - 04:42 PM.

[mullet]

Hi all.  My apologies for going cold (so to speak) on this topic.  I've had a lot on and no chance to look at things.  I will be following all the advice as soon as possible. 

 

Something occurred to me in the meantime.  When I had a prior ignition problem, someone was fiddling with cables (didn't put all back quite right either!).  Is this type of radiator pump mechanical or does it require an electrical supply that might have been disturbed?  Stupid question, I know. 

[mab01uk]

The water pump is mechanical and is not electrical.

Mini water pumps:-

https://www.minispar...ng/1803/180303/

Edited by mab01uk, 14 April 2025 - 02:25 PM.

[stuart bowes]

it's belt driven on the same belt that runs the alternator, it's bolted to the back of the fan itself under that pulley

 

you could check tension on that but I'd imagine you'd be having electrical related issues as well if it wasn't running nice and tight (?)

Edited by stuart bowes, 14 April 2025 - 02:40 PM.

[mullet]

Thanks for the replies.  Had a chance to test things out this evening.  I noticed a kink in the pipe leading down from the top of the radiator (where the cap is).  A pressure/steam/overflow release pipe I presume (but probably with a more technical name than that).  I squeezed the kink out and had the engine running whilst parked for a good 20 minutes.  All rubber pipes eventually felt hot and the internal blower was blowing warm (which it previously only achieved once reaching 30mph/50kph).  The temperature gauge stayed a healthy level even though I was simulating stuck in traffic on a mild day.  Could a kinked pressure/steam/overflow release pipe add THAT much pressure and temperature to stop a normal fluid flow altogether?  I'm going to chance it on a decent run out and will update this thread. 

 

 

. 

[roblightbody]

Just a note, the internal blower should blow roasting hot if everything's working correctly, not just warm.

[mullet]

Just a note, the internal blower should blow roasting hot if everything's working correctly, not just warm.

Thanks.  I remember my first mini some 25 years ago almost.  Passengers in the front not only complained about the hot air, but their shins were in discomfort.  I finally got to drive it today, a mild day.  I took note the heater was blowing warm, not that blasting heat.  The engine also quickly started to lose power after just 8 minutes of driving at around 20 - 50kph.  But it took a while longer for the temperature gauge to suggest the engine was hot.

 

In other words, seems the engine is genuinely too hot before it got hot where the gauge is.  Like there is no longer an even distribution of heat or flow.  I also noticed the pipe from the radiator (the highest level one) was no more hot than any other.  Wouldn't this - located at the highest point - be the hottest if everything was healthy?  Does it point at the pump, therefore?