View Full Version : Overheating issue. Need Advice!

06-21-2007, 09:01 AM
My 1980 Automatic Mini is overheating bad enough that I can't take it on my 15 minute commute to work. We have replaced all of the hoses and put in a new thermostat. Whatever gunk was able to be seen was cleaned out. We've even put in an electric fan which helps a little, but treats the symptoms and not the problem. But, this is what happened:

The car ran fine when I first got it, but then I overheated it while idling. Then, after I overheated it, it would overheat even while driving it. So, it seemed like there was initially a small problem and then it was made worse, so maybe that the head was slightly warped or cracked and then I warped or cracked it more?

Could the same effect have happened with the radiator? Could overheating the car cause something to break free and get lodged in the radiator or something like that?

I've been told to replace the radiator before the head because of price, but if replacing the head is much more likely to fix the issue, then doing that first would be cheaper. Also, if I do replace the radiator, should I go with the super 2 core or the 4 core? Any thoughts?

Thanks everyone!

06-21-2007, 11:28 AM
OK, what is "overheating". Is the car boiling over and venting steam or are you just concerned that the temperature needle is no longer pointing straight down while you drive. Overheating won't be until the needle reaches "H" and shortly after that you MAY see steam after you park. Running above mid-scale on the gauge isn't necessarily a problem, particularly in summer.

Start with the cheap stuff (like phone calls to local radiator shops) before buying any new parts. See if you can't have your existing system reverse flushed and/or if a local shop will rod out your existing radiator.

You said you cleaned out deposits you could see. Have you tried any of the DIY radiator flush chemicals from the parts stores? What you can see is only the start.

If you can't handle this by flushing the system yourself or by having a professional do it, new components are an option. The prevailing wisdom seems to be to use the Super 2-Core in the U.S. I have not used one and am only repeating what others have said.

If the reason you were thinking of replacing the head was temperature related... certainly replace or repair the radiator first. It will cost a lot less.

When (and if) you decide to order new parts to fix the problem you should consider more than just the radiator. While it's out, fit a high-flow water pump. You have a 998 so you'll need to modify the high-flow pump a little bit to fit your block but I'm told the conversion is easy and the results worthwhile. You can also add a higher pressure (13 psi) radiator cap if your car is boiling over. For the summer you may wish to consider running a mix of Red Line's Water-Wetter and water instead of regular anti-freeze.

Again, start with the cheap stuff and move up as necessary. But start with a clean system.

06-22-2007, 06:22 AM
I agreee with Doug...cheap and simple stuff first.

-Not sure what thermostat you've put in. I'd run a 180 F. or even a 165 F. This is not really a "solution", but it can help somewhat.
-Be sure that your fan belt in not "glazed". Even if tight, a slippery fan belt will cause overheating because it will slip.
-Be sure that you do not have *too much* anti-freeze in your coolant mix. Anti-freeze does not reject heat as well as ordinary water. I use 1/3 anti-freeze and 2/3 water.
-When filling with coolant, squeeze the rad hoses to "burp" out all the air. Be sure that your system is really filled up.
-Make sure you have a real Mini fan. I'm not 100% sure on your newer Min, but I think the older Minis have a "reverse" fan that blows the opposite way of most cars (<u>Doug: Check me on this....am I right?</u>). If someone has installed a Sprite fan, the car will overheat.
-If your fan shroud has been removed or is 'away" too far from the radiator, the car may run hot (we fixed this on my pal's 1275 Mini race car and it helped a lot).
-Start the engine, warm it up and rev the engine with the bonnet open. Observe the lower hose and make sure it is not "sucking closed" when the engine revs. The lower hose is under suction from the pump and some cheaper hoses will collapse when the engine is revved up.
-Check ignition timing. If it is retarded, it can cause overheating.


06-22-2007, 07:10 AM
Nial, excellent point about the fan, excuse me for not mentioning it earlier. The fan for the classic Mini blows "out" of the engine bay through/under the left front wing. When you're standing at the front of the car looking at the radiator and fan, the blades will have a "cup" to them. From the front of the car this cup will appear like this:
engine --&gt; <span style='font-family: Arial Black'><span style='font-size: 17pt'>(</span></span> --&gt; radiator
Anyway, the fan cups air and pushes it through the radiator. It's actually very common for people to put the fan on "backwards". With it backwards you'll still get some air through the radiator, just not as much, and the car will run hot.

By all means check how the fan is mounted.

06-22-2007, 09:15 AM
Thanks for all of the advice. When I say the car is overheating, I mean that it's really overheating. And doing so dangerously. I'm pretty sure they didn't install any of the wrong equipment as it wasn't overheating the same way before. I did try the water wetter and it still overheated on a 70 degree morning.

The shop cleaned out the deposits, I'm not sure how they did it.

This weekend we're going to make sure the radiator is working right by testing the temp of the top and bottom hoses to make sure there is a 10% difference between them (I was told to do this by Dion of DJminis) and both Dion and a local mini guy told me to do a compression test on the head, so we're doing that as well. I guess after getting that info, we'll decide what the next steps need to be.

Thanks guys!

06-22-2007, 11:53 AM
Good luck over the next few days. Do work up through the cheap stuff first.

One additional item that could be at fault is the thermostat itself. If it's failing to open things will get hot quickly even on a cool day. HOWEVER, do NOT run the car without a thermostat, it's necessary for the water to flow correctly through the cylinder head. The Mini thermostat crosses over to a common Chevrolet part (see the link below and read through Diagnosing Overheating). This is my friend Todd's Austin America site, but the AA is basically a Mini carrying around a few extra pounds so it's all applicable). See:

06-22-2007, 05:59 PM
Fantastic, thanks!

06-23-2007, 02:28 PM
One thing I didn't see, is mention of replacing or a properly working sending unit. These LBC sending units have a history of when getting hot, going awry.....forever.

So I recommend exploring that avenue first. Get a good heat gauge and take some readings.

06-25-2007, 07:06 AM
Ron also has a good point. Before leaving the issue of questionable instrumentation... how is your gas gauge performing? Does it work and if so how accurate does it appear to be reading? These questions may sound unrelated but they are related and need to be asked.

06-26-2007, 12:24 PM
Gas gauge is fine, temp gauge is slightly off (it reads just a little hotter than it actually is, but not by much).

We ran radiator flush through it last night and also discovered (read: realized) that the cap wasn't keeping any pressure, "Wait, the thing has never sprayed us when we took the cap off when it's hot. DUH." So, we replaced that and it's much better, though still heats up after a while even with the extra electric fan. So, we're going to replace the radiator with one of the super 2 cores and throw in a high volume water pump for good measure. If that doesn't work, then it's time to look at more expensive stuff...

06-26-2007, 03:04 PM
Well, I'm glad it's better. If you combine the Water Wetter, a lower temperature thermostat, and a higher-pressure cap you can certainly buy a little time until you're ready to buy the parts.

In your other thread you were asking about parts prices and vendors. Since you're talking about a new pump and radiator I sought out current pricing so you could see what was suggested in the other thread. My list follows.

The exchange rate on 6/26/07 is almost exactly $2/1GBP

Super 2-Core Radiator
# C-ARA4442
58.00 GBP @ MiniSpares ($116)
219.95 $ @ MiniMania
169.00 $ @ Seven (7ent.com)

High-Flow Pump
# GWP134
13.91 GBP @ MiniSpares ($27.82)
44.95 $ @ MiniMania
44.95 $ @ Seven (7ent.com)

I DO give some business to the U.S. parts sources because I DO want to keep them in business. However, the numbers above are typical of what you'll find when buying "expensive" parts. If you order the parts from MiniSpares, your total will be $144 plus somewhere around $40 shipping and such. (You'll need to check with them on what it really will be.) Combined shipping from CA to the east coast would be about $15-20 for a water pump and radiator.

So, even with the lousy exchange rate and the cost of shipping, when you buy from MiniSpares... it's like you get the water pump for free when you buy the radiator. Plus, you'll have the parts in about 5 days from the U.K. and it will take about 9 days from CA.

Keep us up to date on how the car is running and if your work to clean and flush the system made an improvement.

06-26-2007, 04:47 PM
Thanks! That was really awesome of you to do that. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

And yeah, I did put water wetter in and a higher pressure cap. Hey, I stayed spot on 180 the whole way home, even in the summer heat, woo!

And... The local kids on the street stopped playing basketball, stepped to the side, waved their fists in the air and screamed "**** Yeah!" when I drove by.

06-26-2007, 07:16 PM
180 is great! Save your radiator and water pump money for another day or spend it on something else!!

06-26-2007, 09:11 PM
I'd love to, it doesn't stay there if I drive for more than 20-30 minutes and have to stop for any length of time, though.

06-28-2007, 08:47 AM
I've had the same issue with my bugeye and have had the rad cleaned this last yr. Although better, it has not completely solved the problem. Thinking about the rad as a heat exchager and the reality of cleaning the tubes of the rad it only stands to reason that the tubes do not get all the scale removed. If this is the case, then the heat transfer of this area is just not there. So, this summer, I'm carefully watching my temp. gauge and will probably go to a 3 tube core some time in the future. A friend had this done, the 2 row core had 54 tubes, the 3 row has 97 tubes. Another thought I haven't seen adressed here is drilling some 1/8th" holes in the thermo. It has been mentioned to me by my racing friends and it seems to me as a good idea because it would seem to solve any problems of air in the system. Good luck!

06-28-2007, 10:14 AM
I've heard of drilling holes in the thermostat body but if it's opening "normally" this shouldn't be necessary on a street engine. The holes are supposed to allow air to be pushed out of the system in advance of the water rising as you refill the radiator. The holes really aren't necessary. If you fill the radiator and stand by it while the engine comes up to temperature, all you need to do is continually add more water as you see the level go down in the radiator, then finally fit the cap. A variation that I've heard people use if they don't want to babysit the radiator after refilling the system is to manually push the thermostat 'open' and insert an aspirin between it's housing and its valve (obviously before installing the thermostat on the engine). Once the system is full and the coolant warms up the aspirin dissolves and the thermostat behaves as normal. Before drilling holes, I'd start with a new thermostat (perhaps with a lower opening temperature) just in case the existing one is the cause of the problem. Creatrixx, have you replaced the thermostat yet? Sometimes getting the old thermostat housing off is a bear... I suspect that if you had started to replace the thermostat we would have heard from you.

The Spridget radiators will be different than those on the Mini though obviously similar in size and capacity. The prevailing wisdom among the North American Mini community is to run the Super 2-Core that I mentioned above. However, feel free to research this further on your own.

06-28-2007, 11:55 AM
the thermostat has been replaced and I figure that since the engine stays somewhat cool that it's functional.

I bought a super 2 and one of the high flow pumps for 998s, I'm crossing my fingers.

06-28-2007, 01:15 PM
A high flow pump specifically for the 998? I didn't know such a part existed. The pump I posted the part number for earlier was designed for the big-bore engines but there are ways to make it fit the 998. Which number/model pump did you order?

I'm sorry that it's costing you this much money to get the peace of mind that you want. However, I'll bet with the new radiator and pump the car will run cooler than it ever has.

As an example, I bought a used Accord MANY years ago. The car ran great without any heat related issues while I lived in NY state. When I moved back to NC the car always ran hot and I found myself watching the temp gauge all summer. I finally couldn't stand it anymore and I bought a replacement 'standard' radiator. That change alone brought the engine temp WAY down. The radiator I thought was clean was apparently VERY plugged up and covered with internal scale.

06-28-2007, 03:02 PM
998cc pump: https://www.minimania.com/web/Item/GWP134/AddedFrom/Search/InvDetail.cfm

yeah, I just want to not panic if I see traffic. I'm not too worried though. It'll all work out in the end, I'm sure.

I really appreciate all the help you've given me.

Take care;

06-28-2007, 03:33 PM
That's the one I mentioned.

This is what I wanted you to be aware of:
"This water pump will fit all 1275cc blocks and all 998cc blocks after 1969, and with a slight amount of work on the impeller can be made to fit a small bore block. "

Your car should be late enough that this drops in without issue.

06-29-2007, 09:08 AM
Worse comes to worst, we're going to install it at my boyfriend's place of work where he has access to a mill.