Peugeot 205 GTi overheating after track day

[silver_saxo]

Hi Guys,

Did my 1st track day today and my car held up really well. Only problem was it started to overheat after about 10 laps.

I removed the grill and raised the back of the bonnet up to aid the airflow which helped to start with.

2 sessions of 20mins later and it started again.

Any tips of what I can do to cool it down?

Matt

[Zad]

Presumably the fans are running OK and the thermostat is opening fully. Flush the cooling system to get all the crap out of the radiator?

[Howitzer]

I had a 405 SRI (Pretty much the same engine) and this fixed my warm running problems.

Use a proper 50/50 mix of coolant, I used Peugeots own as oddly it was the cheapest, add some water wetter in it, it genuinely works.

Make sure your rad is clean of debris, fins in good condition, run a flush through but disconnect both hoses when you do this or any crap you loosen may just find its way into the engine, I've run with a pattern part and genuine rad, the genuine one was by far the best, i've not found a non peugeot one which is exactly the same despite what people have told me.

Get a 72° Thermostat, it helps with the temperature for your short sessions as the radiator will be circulating the coolant sooner and will spend more time cooling than say a normal 80° Stat (Available from peugeot also).

Check your rad cap, if it doesn't look very new then buy a new one, any loss of pressure from a cap will cause warmer running also.

Dave!

[That Daddy]

Make sure the smaller coolant hoses are not blocked or restricted (including the barbs they attach to)and then as the others have said, sounds like fair advice

[Daveuk9xx]

silver_saxo said:

Hi Guys,

Did my 1st track day today and my car held up really well. Only problem was it started to overheat after about 10 laps.

I removed the grill and raised the back of the bonnet up to aid the airflow which helped to start with.

2 sessions of 20mins later and it started again.

Any tips of what I can do to cool it down?

Matt

Assuming there's no specific fault like air pockets, blockages or faulty stat there's only one reason why an engine overheats at speed. The radiator doesn't have enough cooling capacity for the horsepower. An old rad with limescale coating the tubes might only have half the thermal rejection of a new one. Not a problem when the engine is pushing out less than 50% of its full power which is the case nearly all the time in road use except for brief periods too short to worry about. Track days and dyno sessions will find the shortcomings in an old rad in no time though.

So fit a new rad. Flushing old ones out never works unless you have it done professionally where the limescale is dissolved out too but that's not worth the bother and if it's that old it'll probably start to leak soon anyway. Fitting colder stats won't work either. A stat can only limit minimum temperature. It can't stop overheating when it's fully open anyway.

Finally. Water has a higher heat capacity than antifreeze so pure water is the best coolant for race use. You do NOT want a high concentration of antifreeze. Obviously you don't want to leave pure water in there for long with an aluminium engine.

Dave

Edited by Daveuk9xx on Friday 27th June 04:05

[Howitzer]

Daveuk9xx said:

silver_saxo said:

Hi Guys,

Did my 1st track day today and my car held up really well. Only problem was it started to overheat after about 10 laps.

I removed the grill and raised the back of the bonnet up to aid the airflow which helped to start with.

2 sessions of 20mins later and it started again.

Any tips of what I can do to cool it down?

Matt

Assuming there's no specific fault like air pockets, blockages or faulty stat there's only one reason why an engine overheats at speed. The radiator doesn't have enough cooling capacity for the horsepower. An old rad with limescale coating the tubes might only have half the thermal rejection of a new one. Not a problem when the engine is pushing out less than 50% of its full power which is the case nearly all the time in road use except for brief periods too short to worry about. Ttrack days and dyno sessions will find the shortcomings in an old rad in no time though.

So fit a new rad. Flushing old ones out never works unless you have it done professionally where the limescale is dissolved out too but that's not worth the bother and if it's that old it'll probably start to leak soon anyway. Fitting colder stats won't work either. A stat can only limit minimum temperature. It can't stop overheating when it's fully open anyway.

Finally. Water has a higher heat capacity than antifreeze so pure water is the best coolant for race use. You do NOT want a high concentration of antifreeze. Obviously you don't want to leave pure water in there for long with an aluminium engine.

Dave

Using pure water is not always a good thing even for short periods. A cooling system is designed around lots of things and the coolant mix is one of these. You can see increased cavitation with lower volumes of coolant due to the mixture itself being less thick (Simplifying it).

With regards to the thermostat, if you are going out for a 20 minute session and after 2 minutes your temperature is at say 82°C because your thermostat opens at that point then running a thermostat which opens at 75°C means you will be starting at a lower temperature in the first place. This means that the coolant will be in the full cooling circuit for longer and may gain you a few extra laps before it gets too hot. It wont decrease your temperature for long runs but for things like trackdays etc it would be a worthwhile addition.

Dave!

[smckeown]

It's more than likely your rad needing to be replaced. Get a cheap lightweight ali Nissens rad; cheap too. If after this temps are still too high, then look at the advised 72 deg C thermostat, decent coolant and water wetter.

Sean

[silver_saxo]

Radiator looks like a good option. Only £50 ish in ebay.

Is there anything I can use to flush the crap out of my cooling system as when I last drained it the water was brown and full of rust (I had only changed it 4 months prior to that!)

[Ponk]

I'd suggest putting your bonnet back to standard. By raising the back you are probably reducing the gap at the front which will in turn be reducing the airflow to your rad and air filter.

[GnuBee]

silver_saxo said:

Radiator looks like a good option. Only £50 ish in ebay.

Is there anything I can use to flush the crap out of my cooling system as when I last drained it the water was brown and full of rust (I had only changed it 4 months prior to that!)

If it's anything like mine was - most of the rubbish is coming from the old radiator.

I'd second the Nissens recommendation, I've just put on mine and there's a substantial improvement.

Just one tip, do not take the old radiator out then patiently re-fit the new one complete with fan switch, spend time tightening up the hoses, tidying up the cables, reinstalling the slam panel only to then end up with wet feet as you re-fill it...there's another bung on the lower left hand side of the radiator.

[silver_saxo]

Ponk said:

I'd suggest putting your bonnet back to standard. By raising the back you are probably reducing the gap at the front which will in turn be reducing the airflow to your rad and air filter.

Not really a problem as the grill has been removed:

[Daveuk9xx]

Howitzer said:

Using pure water is not always a good thing even for short periods. A cooling system is designed around lots of things and the coolant mix is one of these. You can see increased cavitation with lower volumes of coolant due to the mixture itself being less thick (Simplifying it).

Rubbish. There isn't a cooling system made that's so sensitive to the viscosity of the coolant that it stops working if you leave the antifreeze out. The only reason antifreeze is in there is to prevent corrosion and freezing. It certainly isn't there to help cooling. In fact it hurts that to a significant degree because it has a lower specific heat capacity than water. You might want to note the dyno engine temperatures with various coolant mixes in this article.

http://www.circletrack.com/techarticles/ctrp_0507_...

The best coolant is pure water with a surface tension reduction additive. Preferably one that also prevents corrosion.

Howitzer said:

With regards to the thermostat, if you are going out for a 20 minute session and after 2 minutes your temperature is at say 82°C because your thermostat opens at that point then running a thermostat which opens at 75°C means you will be starting at a lower temperature in the first place. This means that the coolant will be in the full cooling circuit for longer and may gain you a few extra laps before it gets too hot. It wont decrease your temperature for long runs but for things like trackdays etc it would be a worthwhile addition.

Again, you don't fix a broken leg with a band aid. Engines need to run at a certain temperature for best efficiency. The standard 88c thermostat gives the best fuel atomisation and economy. For best power you can usually go a little cooler to about 80c. Go any lower than that and the mixture isn't burning properly, excess fuel is creating bore wash and wear. In effect you're running with the choke still partly on.

If the cooling system is designed correctly and in good order you can run flat out all day without overheating. If it isn't you don't fix it by bodging something else.

Dave

[smckeown]

Daveuk9xx said:

Again, you don't fix a broken leg with a band aid. Engines need to run at a certain temperature for best efficiency. The standard 88c thermostat gives the best fuel atomisation and economy. For best power you can usually go a little cooler to about 80c. Go any lower than that and the mixture isn't burning properly, excess fuel is creating bore wash and wear. In effect you're running with the choke still partly on.

Dave

I agree in that running temps are very important, and optimising them is commonly overlooked. Guy Croft Race Engines recommend the following:

Coolant temp 75-80 deg C and Oil temp 85-90 deg C

I have tested the temps with a 72 deg thermostat under normal conditiones and it does run too cool. However, I expect under heavy load (it's natural environment) that these temps would increase som,ewhat to get into the optimal range. I will post my results

[Mave]

Daveuk9xx said:

The only reason antifreeze is in there is to prevent corrosion and freezing. It certainly isn't there to help cooling.

Doesn't it also increase the boiling point? Which must help cooling by avoiding vapour pockets?

[Howitzer]

Daveuk9xx said:

Howitzer said:

Using pure water is not always a good thing even for short periods. A cooling system is designed around lots of things and the coolant mix is one of these. You can see increased cavitation with lower volumes of coolant due to the mixture itself being less thick (Simplifying it).

Rubbish. There isn't a cooling system made that's so sensitive to the viscosity of the coolant that it stops working if you leave the antifreeze out. The only reason antifreeze is in there is to prevent corrosion and freezing. It certainly isn't there to help cooling. In fact it hurts that to a significant degree because it has a lower specific heat capacity than water. You might want to note the dyno engine temperatures with various coolant mixes in this article.

http://www.circletrack.com/techarticles/ctrp_0507_...

The best coolant is pure water with a surface tension reduction additive. Preferably one that also prevents corrosion.

Howitzer said:

With regards to the thermostat, if you are going out for a 20 minute session and after 2 minutes your temperature is at say 82°C because your thermostat opens at that point then running a thermostat which opens at 75°C means you will be starting at a lower temperature in the first place. This means that the coolant will be in the full cooling circuit for longer and may gain you a few extra laps before it gets too hot. It wont decrease your temperature for long runs but for things like trackdays etc it would be a worthwhile addition.

Again, you don't fix a broken leg with a band aid. Engines need to run at a certain temperature for best efficiency. The standard 88c thermostat gives the best fuel atomisation and economy. For best power you can usually go a little cooler to about 80c. Go any lower than that and the mixture isn't burning properly, excess fuel is creating bore wash and wear. In effect you're running with the choke still partly on.

If the cooling system is designed correctly and in good order you can run flat out all day without overheating. If it isn't you don't fix it by bodging something else.

Dave

With regards to the coolant, I ran this engine for 5 years and running with a proper coolant mix gave me the most stable temp, apoligies for having direct experience in it.

The guy wants to use it for track days, if you want to say he must run it at 82°C all day long then so be it, in a perfect world that would be true. Also in a perfect world we would suggest he gets a larger radiator, new genuine water pump, silicon hoses and then start from there, but he's not, he wants to enjoy a trackday and fast road driving, not compete in the Le Mans 24 hour.

As for the cooling system working efficiently, this is an old engine, with no doubt many years of non proper maintenance, possibly corrosion, non genuine bits etc, he either needs a full rebuild to work in these optimised conditions or he needs a solution that should work. Also, the 72° Stat was from Peugeot and was an option on my engine, which is the XU9J engine the same as in the 205 mechanically. Using that stat gives no ill effects.

Back to the OP.

I wouldn't worry about having the grill removed, i'm not sure how the lower bumper is on the 205 but on the 405 there is a strip which blanks part of the radiator held on with 4 screws. If yours has this then removing it opens up the lower portion of the radiator to lots more air.

205gtidrivers.com is a wealth of information on these cars and many people there track them aswell.

Dave!

[Daveuk9xx]

Mave said:

Daveuk9xx said:

The only reason antifreeze is in there is to prevent corrosion and freezing. It certainly isn't there to help cooling.

Doesn't it also increase the boiling point? Which must help cooling by avoiding vapour pockets?

It does increase the boiling point although the main thing that raises that is the pressurisation of the cooling system. At atmospheric pressure water boils at 100c but with the cooling system pressurised to 1 bar that increases to 120c. A 50/50 water/ethylene glycol mix boils at about 107c at atmospheric pressure and 129c at 1 bar.

It's more complex than that though. You need to consider the following.

1) Specific heat of a substance is the amount of energy it takes to raise the temperature of a given mass of substance. For water it's 4.186 kJ per kg per degree C. The specific heat of ethylene glycol is only about 57% of that so a given mass of fluid can carry much less heat out of the engine.

2) Latent heat of evaporation

To make a substance change state from solid to liquid or liquid to gas involves another big input of energy. To make water boil it takes 2257 kJ per kg. That's about 540 times as much energy as it takes to raise the temperature by 1 degree C. That's why if you heat a pan of water on the stove it doesn't take long to get it to 100C but it takes forever to boil it all away. If it weren't for the latent heat of evaporation water would reach 100C and then just go poof and instantly turn into steam. EG only has about 1/3 of the latent heat of water so when it does get hot it boils much more easily.

3) Surface tension.

When a fluid starts to boil at a localised hot spot in the engine (nucleate boiling) little pockets of gas form and the surface tension of the water holds them together. Ideally we want them to burst as quickly as possible and let liquid get into the hot spot to carry the heat away. Here EG scores better than pure water because a 50/50 mix has a lower surface tension.

It's a complex mix of properties with an EG mix scoring a bit better in some areas but a lot worse in others. Summing them all up it takes about 15% more coolant flow with a 50/50 mix to carry away as much heat as plain water does.

What it comes back to is my initial statement that the best coolant is water with a surface tension reduction additive. However if the cooling system is in good order it really shouldn't be necessary to go to such lengths.

Dave

[Mave]

But what's the key constraint on getting rid of the heat? Is it how much heat the radiator can transfer to the air, how much heat the coolant can transfer to the radiator, or how much heat the engine can transfer to the coolant? I took a look at the link showing different cooling temperatures, but that's not what you're interested in; surely you're more interested in how hot the engine is? If the coolant had a really poor heat transfer rate then you'd convince yourself everything was OK because the coolant was cool, but the engine could be roasting!

[Pilky]

Change the temp sender for a start theyre prone for buggering up...

[silver_saxo]

My friend has suggested running pure coolant? Thoughts please!

[Mave]

I think that'll give you the worst performance; lowest heat capacity, and worse heat trasfer and boiling point than a 65:35 mix