15 replies to this topic

[corsicanwood]

Hi everyone, here's my first topic as i browsed the search function for months now 

Also I'm french, I hope my english will be understandable.

 

My mini is a 998 with a stage 1 fitted, AAU needle in the carb.

 

For 2 years I've seen it overheating, slightly in winter, and a lot more in the summer. The seller told me that the radiator might be old and muddy so, I bought a brand new 3 core original radiator, but the car still overheated.

 

I flushed the water system a hundred times, changed the thermostat (I tried all of them, even the special ring), all the hoses and the water pump (high flow), the heater matrix, the heater tap, the whole speedo unit (facing the driver -> central speedo) and fitted the sender that came with the speedo, I've tried a small waterpump pulley... And the mini overheated even more... 

 

I started to be really annoyed, some garage and friends told me the problem could be the head gasket (as the top and bottom hose of the radiator were really hard to squeeze, and when I ran the engine with the rad cap off, I could see a lot of bubbles when hot), so I fitted a new head gasket. 3 times in the same year, because the problem was still there. I also changed the cylinder head 2 times, thinking it was cracked...

 

 

This summer I was really cranky to not use my mini, so I fitted another engine, still a 998, thinking my block was cracked or something. The new one overheated like the original. 

Eventually I realized that my heater only produced heat while driving, but was cold while idling. I incriminated the heater tap, which was leaking, and air was entering the system while cooling overnight.

 

I replaced again the sender, and the heater tap with a simple steel take-off, and the heater is hot all the time now, and the temp gauge decreased from H to maybe 5mm after the N of the gauge. I still have a lot of pressure in the rad hoses though. 

 

BUT : 

 

If I start the car, and let it heat in my garden without driving : the thermostat opens and the gauge stays between C and N. 

If I drive in town : the temperature stays a little below the N, fluctuating sometimes. 

If I go up a hill, or drive at 60mph on a flat road : the temperature gauge start to creep up. In winter too... If I go down a hill, the gauge decreases towards 1/3 of the gauge.

 

The timing is set to 10° at 1500rpm, the carb is tuned and besides all of that the car runs great.

 

Calling specialists here 

Thanks in advance.

 

 

edit : MS, sorry for the language. I didn't even know how to politely say the word that you deleted...

Edited by corsicanwood, 09 April 2019 - 12:01 PM.
I know yr new here, but please mind the bad language - thank you

[Spider]

Wow !! That is some work you've done here !!

 

Two things that poke me in the eye here.

 

1 - forgetting the temp gauge in the car - have you measured the running temp with a known reliable gauge ? Before doing anything else, do this next.

 

2 - I know you've 'flushed the block' but have you done this with just water or used some chemicals to remove the rust from it? This is important and will lead to over heating.

[corsicanwood]

Hi ! Ahaha yes, I did worked a lot on it... Thanks for your response !

 

1 : I've tried two gauges : the one from the original 2-clock speedo, and the one from the central speedo. Maybe I could try another, but the gauge now fitted is accurate when the thermostat opens, why would it fail later ? 

 

2 : I tried hot white vinegar, and soda ash (I don't know if the traduction is good for that) it's Saint Marc, well used by old french mechanics to clean hard deposits (rust, limestone) while not attacking hoses or the copper of the rad. After that, i rinsed the system again and again, really 15 times at least with clean water. Not any cleaner from the automotive market has been used.

[Spider]

1 : I've tried two gauges : the one from the original 2-clock speedo, and the one from the central speedo. Maybe I could try another, but the gauge now fitted is accurate when the thermostat opens, why would it fail later ?

 

I'd strongly suggest using something other than a gauge from the car. Granted, I see you swapped it, but I wouldn't trust that.

 

Measure the running temp with something known and reliable - then you have a true base line.

 

Something like this is quite good and none too dear;-

 

https://www.ebay.com...j8AAOSwPhdVAozd

 

get the car up to 'temperature' then point it at the thermostat housing or the top tank on the radiator. Would be exact, but it will be within 1 - 2 degrees.

 

You can easily check the IR Gun on blocks of Ice (be around -4) and also on boiling water (around 100).
 

Only then will you know.

[DeadSquare]

When you fitted the alternative engine, did it come with a fan, or are you using the fan from the original engine ?

[corsicanwood]

I will try, I just wait to borrow one.

 

But if the gauge was out of "tune", why would it sit on the desired spot when the thermostat opens, when I don't drive ?

[Rorf]

Of concern is the radiator hoses going hard - do you have the correct pressure releasing radiator cap; are you using an overflow tank and are the caps on correctly.

 

Maybe your compression ratio is too high.

Edited by Rorf, 09 April 2019 - 11:29 AM.

[DeadSquare]

Many years ago at Silverstone, I solved the overheating of one of the works cars.

 

Their fan was sucking air through the radiator from the wing instead of blowing it through the radiator into the wing.

[corsicanwood]

@Rorf, I have a pretty new 15lbs rad cap, as fitted when I got the car. It's nice and tight, and my mini doesn't have an overflow tank... My compression ratio is, I guess, standard... Not the head nor the block were modded, everything is stock besides the stage 1.

 

@Deadsquare, my fan is fitted the right way  and i can feel the heat while driving with my hand out of the window. And the new engine dit not came with a gearbox anyway...

 

I used my old belt-driven plastic fan, as the engines were the same.

I did not have an electric fan by the way. But even if I had one, it wouldn't help because the car overheats at speed...

Edited by corsicanwood, 09 April 2019 - 11:48 AM.

[unburntfuelinthemorning]

Is air able to flow freely through the front grille?

[Gilles1000]

I would also check the carb to see if the engine does not run too lean or too rich. I assume the needle to be ok from beeing a stage 1 kit.

Could be a root cause as well...

Is your air filter clean? Does it breathe well?

How do the spark plugs look?

[corsicanwood]

Is air able to flow freely through the front grille?

Absolutely ! 

 

I would also check the carb to see if the engine does not run too lean or too rich. I assume the needle to be ok from beeing a stage 1 kit.

Could be a root cause as well...

Is your air filter clean? Does it breathe well?

How do the spark plugs look?

 

The needle is the one usually fitted with the stage 1 kit. My air filter is new and clean, the car starts instantly in the morning without choke but struggle to accelerate without it (only when the engine is cold). So I guess the carb is pretty well tuned...

But the spark plugs look strange...

 

Edited by corsicanwood, 10 April 2019 - 08:13 AM.

[Rorf]

Strange copper residue there, but otherwise it appears to be rather on the lean side. What fuel are you using?

[corsicanwood]

Strange copper residue there, but otherwise it appears to be rather on the lean side. What fuel are you using?

It looks very lean on one side, but perfect on the other 

 

I use Unleaded 95-E5, the only fuel available in Corsica

[Rorf]

 

Strange copper residue there, but otherwise it appears to be rather on the lean side. What fuel are you using?

It looks very lean on one side, but perfect on the other 

 

I use Unleaded 95-E5, the only fuel available in Corsica

 

Maybe too much ouzo in the fuel