Hot Running 1380

[MiniDave]

After I rebuilt the engine in my 1980 Clubman Estate, it ran hot.....but the weird thing is it only did it on the highway. Around town it actually cooled off. Once back on the highway it would slowly creep towards the red. It took a long time for me to understand why and along the way I not only changed the radiator to a 3 row (the car came with a rad for the 998 that was originally in the car) I decided to add an extra cooler - it gets frickin hot in Kansas in the summer so I wanted all the cooling I could get.

Just as I finished engineering the aux cooler I found the real culprit, the oversized water pump pulley. When you run short gears like the OEM 3:44, it turns about 4500 rpm @ 65 mph, but I put the 2:76 gears in it, which means it turns about 3000 @ 65 - when you're turning fast like that you need the big pulley so the water pump doesn't cavitate. Running the slower RPM that I do the water pump just wasn't moving enough water on the highway.

I've had a few discussions about how to plumb in the aux cooler - most people said plumb the return from the aux cooler to the lower hose, the theory being you're sending cooled water right into the block instead of mixing it with the hot rad water.
I think this might work on race cars, but on my car it wasn't doing it, so today I made a small change and now I run it into the top hose. We'll see who's right come this summer!

One thing I found tho, I might not need the aux cooler at all (I put a ball valve in so I could shut it off in winter) as once I changed the water pump pulley back to the smaller one, now I can't even get it up to the thermostat opening temp of 185 on a 70-75* day! I won't know for sure till it gets hot again in a few months.....

Here's what it looks like now.....



The black hose comes from the outlet end of the aux cooler (a heater core from the back of a F-350 Ford van - 21" long by 3" wide and 2" deep!) goes into the top blue rad hose. That blue hose is actually a lower rad hose shortened to fit. I also have an electric fan on a switch in the cabin, just in case - but I don't think I'll need it either.

[MtyMous]

I envy the amount of free space you have in the front of that clubby nose.

[94touring]

I envy the amount of free space you have in the front of that clubby nose.

I was thinking the same thing.

[MiniDave]

Yes, it does allow some mods to be done more easily - and any Vtec conversion is an easy fit. OTOH, look what the Project Binky boys are cramming into the front of their round nose Mini!

Mike Guido says I'm doing it wrong, and while I follow his reasoning, I'm not sure I agree with it. Like I told him, we'll see what happens this summer when it gets hot. Right now I'm having trouble getting it up to temp, let alone running too warm.

[MtyMous]

Well my first question would be in reference to "shutting it of", where is the feed to the radiator come from? If it comes from the clutch side of the head takeoff, i wouldn't recommend blocking that. Too many horror stories about hot spotting in the head.

[MiniDave]

I'll post up how I did it, but basically I built a block that went below the heater valve to carry off the water, from there it goes thru the shut off ball valve (when open) and then into the heater core mounted down low in the grill, from there it used to go back into the lower hose and back into the block, bypassing the radiator. Now it goes into the top of the radiator - bypassing the thermostat but thru the radiator before back into the engine.

Guido might be right in that he thinks the first way I did it was the better way, we'll see.

[MtyMous]

Well there's always room for experimentation. Mike definitely knows his stuff, but there is the idea that a second level of cooling couldn't really hurt. Many have thought of plumbing into a thermostat housing would improve flow and cooling. I guess we will find out with your setup.

God speed

[MiniDave]

Took it for a 50 mile each way drive yesterday, it was about 50* out so not much of a test but I cannot get it to warm up past 165*, and I know I have a 180* thermostat in it. I've never had a car that wouldn't at least hit the thermostat opening temps on a 50* day.

I'm gonna hafta wait for hot weather this summer to see how it does in the heat.

[MtyMous]

You shouldn't have a problem getting up to operating temp. It sounds like your t-stat may be stuck open (even if just slightly). I'd crack it open and give it a look. If it's not stuck open, then you may want to check it for proper operation. It won't cause you too many problems, but I bet if you popped the valve cover open you'd have a good amount of mayo under there.

Was this drive with the extra rad "open"? If so, then disregard my previous statement and close it. lol

[MiniDave]

No, the aux is closed. It's a new thermostat, and I boiled it to see if it worked properly - it did.

Perplexing.

[MtyMous]

That is pretty interesting. I mean. I guess it's possible that you could just have a really really good cooling system. But I can't imagine it having a problem getting up to at least op temp. I'll have to wait for more pics/info on the system  I guess.

[MiniDave]

I've made three major changes since this summer. 1) I replaced the radiator and put in the warmer thermostat 2) it got colder out 3) I changed the water pump pulley.

Of those, the pulley seems to have made the biggest difference.

It is perplexing, so till it gets hot out I'm not going to worry about it. We'll see what it does when it starts hitting 80-90° this summer or late spring.

[MtyMous]

You didn't drill a hole in the thermostat by chance, did you? I doubt it would make that substantial of a difference, but I'm curious. Heater core (inside car) isn't open? My curiosity is piqued if you couldn't tell. haha

[MiniDave]

I did not drill a hole in the thermostat, no.

Heater valve is new and I don't feel heat from the core unless it's turned on.

I'm just as curious as you are......like I said, I've never had a car that wouldn't get up to the thermostat setting, even on a cold day, let alone on a long highway drive on a 50° day.......

[MiniDave]

I took the car for a 180 mile run last weekend, on the way down it was only about 50° out and we had a strong tail wind. The temp ran about 165° as it's been doing. One the way home it was about 70° ambient and it was interesting, the temp got up to 180-185° then the T-stat would open and it would drop back to 165° again, then slowly work it's way back up to opening temp again. Strange.....never seen a car do that before.

I'm confident that I don't have an air bubble or anything, I get plenty of heat out of the heater core, and of course the extra core in the front was shut off.

I'm not going to worry about it till it starts getting HOT out, then we'll see what it does. We have a run scheduled for next month over spring break, it should be warmer then so that should be a good test also.....

[MiniDave]

Well, it finally got hot enough to give my cooling system a real test, I've had the extra cooling core open all summer, but the other day I did a 60 mile highway run in 95* temps, it ran between 180-190 all the way....

I think the way I plumbed it is OK....looking at the aux radiator setup from the factory on Aussie cars - they did it differently, in essence just adding another radiator to the front of the car and plumbing it in series to the original rad - so the water comes out of the T-stat and into the front rad, then from there straight into the top of the side rad, and then back into the water pump. If I were running in hot conditions all year I'd simply put a modern aluminum rad in the grill with an electric fan behind it and dispense with the side rad altogether, but my system seemed to work just fine this summer, so I'm calling it good!

[94touring]

Very good.  I did my OKC trip today.  I'm finally staying at N regardless how hard I drive.  Temps try to creep in traffic but the aux fan kicks in and pushes it right back down. 

[John Gervais]

Nice - you've still got summer temps over there?  Autumn has hit us hard; cold, windy and rainy. 

Had a break in the weather last Friday, so I took the mini up to the estate and cut the grass.  It's currently fitted with an 82C (180F) thermostat and the trip is 100km (60 some-odd miles) each direction, 80% of that is motorway.  Speed limit here is generally 110kph (68mph) on the highway, so that's around 4000 rpm.  I struggled to maintain 81C, but it did climb to around 84C when I brought the mini up between 5000 and 5300 rpm (about 85-90mph 3.44FD, 165/60/12). 

I think I'm running a bit rich still, as fuel economy was a bit down, so hope to have this sorted soon.

[MiniDave]

Yeah, still 90's here (32-35C), but in a week or two it will start to cool off.....

84C is not too hot.....about 185F......

[John Gervais]

I expect the temp to increase slightly once I get the top-end mixture sorted.  I've a feeling that I'm 'quenching the flame'...

[Air2air]

If you guys want to hear a weird one, a few people were telling me to lose the oil cooler.  I swear my temps actually went down.  It's unusual to get past the halfway mark.  Plus I can actually get to the starter, dizzy etc.  I do always have the heater on as well, just not the blower.

[94touring]

It's still pretty warm here.  It hit about 90°f out on the drive back.  I was doing 70-75 the whole way.  Averaged 29.8mpg too. 

[MiniDave]

Air2air, maybe the oil cooler blocks enough air that it can't flow freely thru to the radiator?

I've often wondered about those guys who mount 4 giant driving lights in the grill, and whether that affects the cooling.

In my case anything over 80* caused mine to run hot - till I changed the water pump pulley, then it took sustained drives in temps above 90. Now even that doesn't bother it.

[94touring]

I tried running it without the fan on but that didn't work at all.  Air just doesn't go through the radiator at speed.  Eventually I'd still like to do the electric pump, no fan, and then fab up a shroud that forces ram air through the radiator.  The aux fan would be there for sitting at a stop. 

[John Gervais]

Air2air, maybe the oil cooler blocks enough air that it can't flow freely thru to the radiator?

I've often wondered about those guys who mount 4 giant driving lights in the grill, and whether that affects the cooling.

In my case anything over 80* caused mine to run hot - till I changed the water pump pulley, then it took sustained drives in temps above 90. Now even that doesn't bother it.

Ah, yes, I also changed water pump pulley back to the small one.  The 4-blade fan is noisier, but it seems to be working.