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Overheating Ideas.


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#1 Theotherscottj

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Posted 14 July 2018 - 09:55 PM

Hi all, hopefully an obvious question and answer session here.

Running a 1275cc A+ Cooper engine (according to the numbers) was a 998cc Mayfair.

I've noticed that the car really struggles uphill after a 15 mile or so drive for example. I occasionally drive home from work on a Friday with it and it's rush hour traffic so engine is usually been running for 40 mins and I take A roads home for half the journey so a steady 50 mph for around 5 then rush hour B road.

I start losing power uphill and notice the temp gauge hitting around 75%, it seems to do this around 50mph mark after a longer or spirited drives on not so steep inclines.

I'm taking it to the garage on Monday and plan to swap out radiator, got a Fletcher ally one with all new silicon hoses. I'm going to get a new pump and a new thermostat as I'll be taking everything out so makes sense.

Could this overheating be down to this or should I be looking elsewhere?

I've put new sparks and dizzy cap on last few weeks and no change. Was plenty of oil but again I'll double check that when in garage.

Sorry was longer than expected!

#2 Theotherscottj

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Posted 14 July 2018 - 09:56 PM

Water pump I meant by the way

#3 cal844

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Posted 14 July 2018 - 10:27 PM

Try flushing the coolant system with CLR

#4 Theotherscottj

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Posted 15 July 2018 - 12:17 AM

Try flushing the coolant system with CLR


I'll definitely be giving it a clear out. Be interesting to see what comes out of the old rad.

#5 Moke Spider

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Posted 15 July 2018 - 03:49 AM

When trying to analyse an overheating issue I try to break it down in to one of two categories;-

 

     1 - is the engine simply making too much heat, or

 

     2 - is the cooling system unable to dump the heat it's receiving.

 

Considering 2 first, a fairly simple check for that is once running hot, how long does it take (while on easy running) does it take to cool down to normal temps? Obviously some experience with these cars is needed to have a decent feel for this, but it should take about a minute to come down from around 92-ish to 82-ish on the cruise. There are always exceptions to this though.

 

If it's 1. above, and given your description, I'd be looking at the overall tune of the engine (right needle & carb spring, right dissy curve for the engine) as that would probably be close to the top of the list for reasons for hot running, and a close second to that is as cal844 hinted at, a rusty cooling jacket. They say 1/2" rusted plate, has the same heat transfer qualities as a 6 - 8" slab of steel.

 

None the less, I would strong suggest all aspects of the cooling system be examined, even if you think you have found the issue and it behaves better, I'd still suggest looking at everything.



#6 Carlos W

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Posted 15 July 2018 - 06:15 AM

Check to see if it's running lean before spending a fortune on shiny new parts.

Also check the timing and make sure it's advancing correctly

#7 MatthewsDad

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Posted 15 July 2018 - 07:29 AM

Good advice above. I'd hang fire on spending money for now, and have worked through the basics. When did you last flush the system, and is the engine nicely tuned? Not sure whether an aluminium rad and silicon hoses are necessary under most circumstances, although they do look good 😁

#8 Theotherscottj

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Posted 15 July 2018 - 08:21 AM

Current rad is a bit rusty and looking a bit old hence the replacement. I've had the mini a few weeks so this will be the first time getting it up on a ramp and having a proper look.

Flushing the system was going to happen regardless of the rad, as although previous owner seemed to keep a good book of receipts not sure what his maintenance was.

It does take a bit of time to come back to around mid way on gauge (I drive maybe once a week so I'm a little vague here)

I'll get the carb looked at the same time, one first start up and idle etc car sounds great and when warmed up the same. It just seems to be once I'm in slower traffic and have a decent hill to climb.

I'll make a note and report back, cheers all.

#9 Bat

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Posted 15 July 2018 - 08:59 AM

Hi,

As said above check timing and mixture, particularly that the distributor is advancing and returning correctly afterwards.

It could be that the engine is just too hot causing the lack of power.

BMW have an electric heater in the thermostat so they can lower the temperature when you put your foot down to make more power as the engine normally runs really hot to keep emissions down.

Cheers  :proud:



#10 Theotherscottj

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Posted 15 July 2018 - 08:09 PM

I'll pop the plugs out have a quick look and see any obvious mix issues.

Does help having a mate who has a garage though hoping to do most of this myself (just steal his tools)

#11 russo

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Posted 15 July 2018 - 10:47 PM

A simple leak down test will tell you if the engine is making too too much heat. ie blown cylinder head gasket or cracked head.



#12 Moke Spider

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Posted 16 July 2018 - 12:51 AM

A simple leak down test will tell you if the engine is making too too much heat. ie blown cylinder head gasket or cracked head.

 

Yes, that'll show up a blown head gasket for sure.

 

Respectfully, it doesn't always show a cracked head, rarely in fact as the cracks are only small and really only open up when hot. The leakage that will show up in such a test is usually considerably less than that you'd get via the rings.

 

In respect to the engine making too much heat, that could come from the ignition timing being either too far advanced or retarded (or just simply the wrong advance curve) or a lean fuel mixture. Or a rusted cooling jacket. None of these would show up in a leak down test.



#13 Theotherscottj

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Posted 22 July 2018 - 08:36 PM

Overheating seems to have calmed down, mix looks fine as a light golden brown colour on sparks, if anything maybe worth making it richer?

After a quick drive about in the dark mechanic mate in passenger seat, we've decided carb needs to be looked at.




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