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UPDATE
I replaced the radiator, radiator cap, hoses, thermostat housing, and thermostat. I also added oil to the carburetor dashpots. The radiator installation was quite a challenge and coercing the silicon hoses to fit was no fun either. It took a bit of stretching and silcon spray lubricant to complete the installation. The new radiator came with a drain plug allowing me easily flush the system. All of the new bits were sourced by our host. (Thanks Jemal for your help and patience guiding me through the process.)
The car no longer overheats, there are no coolant leaks (no more boiling out), and the temp gauge reads consistently a bit past the "N" while driving. I've taken the car out for several drives between 5 and 15 miles, so far so good. The temp does start to climb while idling at a traffic light but falls back when in motion.
A couple more important notes; the engine "run-on" has only ocurred once since the I've installed the new radiator and the engine idle is no longer climbing.
The auxiliary fan and new heat diverter valve arrive in a couple of days so there some additional tinkering planned. I'll be starting a new thread regarding auxiliary fan installation on "positive earth" cars when it arrives. I'm sure that'll be interesting.
Thanks to everyone for the helpful posts.
1967 Austin Mini Cooper S
1970 Austin Mini Cooper S
1973 Innocenti Mini Cooper Export 1300
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I'll agree with the proper needle and over heat. After building a new engine /tranny and replacing all suspension and brakes on Alex's car two years ago I had issues with over heating on 100 plus days. Not having any more money or time to spend on it I place d the car on jack stands for 2 years. In that period I picked up an O2 gauge. Once I put it on the car I realized I had reached a near perfect 15.9 to 1 A/F ratio seat of pants. A simple needle change and I was in the 13.8 to 14.5 range. I have not installed the gauge in the car. Under load and at sepped over 40 mph I think it's going rich. I have spent hours looking though needle charts. There is nothing in the book that looks right. I'm talking with some of the UK guys about making me a few one off needles. I'm going to try a few myself. I have a good idea what the first 4 stages are after that I need to lean down. It had not occured to me I'd be running 70-90 so much of the road trip. Steve (CTR)
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Prior to repacing the radiator etc, add to your intial task list to check the fuel mixture, as a lean mixture will cause an engine to run hotter. Also install a new radiator cap. These are both simple items to address which may be adding to your problem if not correct. If you are going to replace the radiator, while it's out you might want to also consider replacing the water pump, belt and bypass hose (if fitted), unless you know these items are all relatively new.
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So I had a lot of overheating issues when I got my new 84' Mayfair (1275+). I fine tuned my timing, ended up at approximately 29 @4000 rpm. In the end, I replaced my water pump and put in a 3 core radiator. What was the final thing that put me to do these final additions after I nailed down the timing? I ran it till it was overheating, then shut it down and took a real good look at the radiator, it had real fine pin holes in it at multiple loactions. If the the radiator cant seal it self, it will boil over. I am using a 15psi cap. In the end.. New radiator, new water pump since I was in there and did not know what had been done previously. Radiator fluid at 10-20 % water to coolant with some water wetter. I'm in Maryland and have not had any issues sine last year. Good luck...........
Jason
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Thanks to everyone that responded.
Here my task list.
1. Check carburetor dashpots
2. Check ignition timing.
If it still overheats after running idle for 15 minutes,
3. Replace radiator, hoses, thermostat, and thermostat housing.
If it still overheats after running idle for 15 minutes, seek professional help. (for the mini too!)
1967 Austin Mini Cooper S
1970 Austin Mini Cooper S
1973 Innocenti Mini Cooper Export 1300
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Just to clarify. The coolant level drops a bit, as you say, when the thermostat opens up. Of course, the coolant expands as the engine gets hotter. My point was that thermostat does appear to work.
1967 Austin Mini Cooper S
1970 Austin Mini Cooper S
1973 Innocenti Mini Cooper Export 1300
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It could be any number of things but the first thing to do is check if it's actually getting hot or not? do not rely on the temp gauge for this, use a seperate gauge or one of those laser gun chappies to determine the actual temp. Water from the overflow could be simply a bad cap or as already stated an overfilled radiator. it's always best to get an accurate diagnosois before swaping out parts but you seem to realise that, goodluck...................
Mini's are like buses they come along in a bunch
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Check your ignition timing is correct as this affects the temperature, as it is dieseling it may be off or could be simply due to the high idle.
Also check that the dashpots on the carbs have oil in them - since you've only had the car 2 months, maybe they need a refill. Lack of oil would affect mixture and produce poor running and possibly overheating.
You also mention the coolant level drops when the thermostat opens. I don't think it should.It may go down a wee bit if you gun the engine with the rad cap off, but retirn to the same level. In fact it should come up as the coolant expands with heat.
You are leaving some air space in the rad, aren't you? It should be left about 1" below the neck of the rad. Modern cars with separate expanson tanks have their rads filled, but not Minis without expansion tanks.
.
"Hang on a minute lads....I've got a great idea."
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"I can feel hot air blowing through the left side fender." .......The fan will blow outward regardless of the way its installed. It works better installed properly.
Absolutely. When I got mine turned around I could use the Mini to blow leaves out of the garage. ( We're talking about the plastic 11 blade fan, not the older metal one.)
.
"Hang on a minute lads....I've got a great idea."
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Check your ignition timing is correct as this affects the temperature, as it is dieseling it may be off or could be simply due to the high idle.
If in doubt, flat out. Colin Mc Rae MBE 1968-2007.
Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.
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"I can feel hot air blowing through the left side fender." The blades have a flat side and a slightly convex side. The flat side should be facing the rad. The hub has a flat or smooth side and a flooted side. The flat/smooth side should mounted on the pulley (the side with the flutes faces the rad). The fan will blow outward regardless of the way its installed. It works better installed properly.
The power of accurate observation is commonly called cynicism by those who have not got it. G.B.S. Sarcasm is the lowest form of wit. Oscar Wilde
//www.cupcakecooper.ca/
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I had similar problems last summer with my 1293. I changed to a 4 core Minispares radiator, new plastic fan, new aux fan, 50/50 coolant with Water Wetter, 190 degree stat (so it will run when it's cold out) 13lb cap (I think I'd need to look) New hoses and flushed the system. The car now will only have the aux fan come on when I sit in traffic on 75+ degree days. On my dash temp guage it registers just below half way before it would go to around the 3/4 point.
I found the dieseling to be caused by the heat in the engine and low octane fuel I run either VP 100 octane race gas mixed 50/50 with 93 pump gas or 93 pump with Torco octane boost. The car really likes the VP fuel, the Torco stuff works better than any of the other octane boost stuff I've tried.
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"dieseling" in most cases is due to carbon deposits in the head..
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I just checked the thermostat housing and noticed that some of the gasket sealer has extruded through the thermostat housing and top of the engine block.
I just wanted to make sure the problem has been properly diagnosed before replacing the radiator and related items.
My concern is that it may be more serious like a hairline crack in the head.
Thanks for posting. -Sal
1967 Austin Mini Cooper S
1970 Austin Mini Cooper S
1973 Innocenti Mini Cooper Export 1300
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It'll diesel if its as hot as you say, so that could just be a symptom of the problem. Is it the original rad with the tubes going through cooling fins at right angles. Supercool rads with the fins zig zagging between the tubes provide 30% better cooling. There's a better than average chance the fan is on backwards, putting on the right way might help some but it doesn't really account for the slow deterioration. Also a higher pressure rad cap might stop the expelling. Is the fan belt tight, although usually the alternator doesn't work either with a loose belt.
The power of accurate observation is commonly called cynicism by those who have not got it. G.B.S. Sarcasm is the lowest form of wit. Oscar Wilde
//www.cupcakecooper.ca/
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Looking for advice regarding constant overheating issues on my 1970 Austin Mini Cooper S. It’s a genuine Mini Cooper S with twin SU Carburetors, not a Re-Vin.
I’ve had the car for just about two months and it ran great for the first 5 weeks. No major issues, just some minor maintenance to get it past a routine Massachusetts inspection; new battery, swapped out worn tires on original steel wheels with Yokohama A008s mounted on Mini Lite wheels, and windshield washer jets (yes the inspection station is very picky).
I also replaced the cartridge style oil filter canister with a “spin on” oil filter adapter and applied more fluid to the hydrolastic suspension for more wheel clearance. (Yokohama A008s mounted on MiniLites are a bit taller than the original wheel /tire combo.)
All of this was done within the first week after acquiring the car and I was able to successfully pass the Massachusetts inspection. The car was initially driven nearly every day taking short trips after work and longer runs on weekends mainly to shake out any problems.
After the 4th week, I noticed the temperature gauge constantly climbing first only when idling at a light, but now all of the time even on a short 5 mile run. The car constantly expels water from the radiator overflow hose. Basically, the hot engine is causing the coolant to boil out.
The thermostat was also swapped out and still no improvement. The water pump and thermostat appear to be working because I can see the coolant drop when the engine warms up. Also the radiator hose from the thermostat housing to the top of the radiator is warm. The radiator fan pushes plenty of hot air through the left side fender as it should. My concern is that I may be treating symptoms and not the actual cause of the problem. Finally, one more important note. The car idles normally when started. Cold starts require the choke to be opened just a bit. However, the engine idle climbs. (There’s no tachometer so I can’t provide a specific rev count, but it is definitely idles at higher revs after running a bit.) The engine also “diesels” quite a bit after running requiring me to put it in gear and lift the clutch to shut down.
I can’t help but believe that these issues are related. This is a 44 year old car and I am prepared to replace the radiator, hoses, and water pump if needed. I know an electric fan would help. However, I do not believe the car should overheat after a 5 mile run.
Any thoughts or advice would be appreciated.
Thanks in advance. Sal
1967 Austin Mini Cooper S
1970 Austin Mini Cooper S
1973 Innocenti Mini Cooper Export 1300