Cooling System Issues

[Guest greavesy7]

I design radiators for f1 teams and one of the main reasons that they don't have them at 90 is so that they can increase the surface area on the core in the side pods

[Guest greavesy7]

The down side to slanting the core would be an increase in the pressure drop from the front to the back of the core but along as you have enough airflow this should not be a problem.

 

 

[Guest Dan_Norfolk]

Thanks again for the additional info, I will start by taking out the thermostat and checking what temperature it opens at; if it is higher than 82C then I will replace it for a lower temp one. I know that the thermostat works as the car has overheated a couple of times and spits water and steam out of the top of the radiator. I will also look to test the water temperature as it exits the engine, possibly by using an infrared temperature sensor aimed at the pipes and rad corners to track the differences across the system.

 

The car has overheated after a couple of short runs (displacing about a litre of water/steam) and also whilst idling on the driveway.

 

Both fans are sitting in front of the radiator so I will remove the one just behind the front grill first to see if this improves it and then look to replace the second fan with one that sits behind the rad. Also, I will check to see if there is any need to block around the edge of the rad to stop bypassing.

 

Richardm6994, my interpretation of the above responses with regards to the angled rad is that if it is at an angle then a radiator of equal size would be less efficient if it stands vertically in comparison to one at an angle of say 30 degrees, however by having the radiator at an angle you are therefore able to fit a larger radiator and this is where the advantage comes in terms of cooling capacity. Please correct me if I'm wrong.

 

I'm away for a couple of days so I will take a look over the weekend and see what I can come up with.

[Longboarder]

The car has overheated after a couple of short runs (displacing about a litre of water/steam) and also whilst idling on the driveway. I assume with the rad cap still on and it did not do so on the long journey. get the system into full checked working order.

The manifold to waterpump pipe is relevant to warm-up bypass only (unless it is too large and can 'steal' significantly from the rad flow) and an air lock will stop/reduce flow here so it should not affect cooling capacity unless it is preventing filling of the cylinder head waterways. Not quite sure how it would do this but re-route it round the back of the block to be safe.

To get good flow of coolant through the system its component parts must be working. Remove water-pump. Check the vanes are in good condition and that the vanes will not turn separately from the shaft. Some are cast alloy vanes and boss press fitted to the shaft. Some are bent steel press fitted or welded. They can come loose so the pulley and shaft turn but the vanes partly freewheel.

Remove the stat housing, Check the stat operates fully. Even better buy a new one, your choice of opening temperature. Make sure you fit it the right way round, spring and wax bulb go toward the head side, not into the housing. Drill a 3mm hole in the plate so it is at 12 o'clock when fitted. This helps air to bleed out of the head.

Check the hoses are in good condition. Remove and look down them with a torch, run a blunt stick/screwdriver down them to check if the inner surface is intact. Any cracks, splits or breakdown of the inner surfaces could mean a flap is lifting in the flow and reducing flow.

With the hoses off flush the rad both ways. Does water pour through faster than the hose can supply? Should be OK then.

Do you have any sort of overflow/catch/header tank. Fit one if not. It is the only way to keep the rad topped up and a simple spit/suck-back system will bleed the rad for you when driving.

Buy a new standard rad cap.

Fill with water and anti freeze mix. Run engine up to temperature with the cap off and stand by with more mixture to keep topping up. As it gets hotter air will bubble out of the rad. Keep topping up. The fan should cut in at say 85 and off again at 80. Check it's moving air from in front of the rad towards the back of the car! Unless there is another problem the engine should settle at idle with the temp mid 80's and the fan cutting in and out. It should not boil. Switch off, top up one last time and refit the cap. The overflow catch tank is fitted, yes?

If all these things are checked then you know it is not a water circulation problem. (Always boil test a new stat, check new parts before fitting!)

The only thing likely to catch you out is if the engine refuses to stop bubbling air out the rad while you keep it topped up and rev it a few times. This could mean a blown head gasket and this could be the only symptom. You don't always get mayonnaise on the underside of the oil filler cap.

That's given you enough to do for now. Next air flow and miscellaneous causes like weak mixtures and retarded ignition.

 

Nigel

[Longboarder]

Not meaning to hi jack this thread, but just a quick question picking up on Nigel's comment? Please don't take this the wrong way because I'm not argueing what you have said Nigel, but I'd like to know more about why the radiator at an angle is more efficient than if it was at 90degrees?

Don't know. Less air turbulence/higher pressure contact on one side of the cooling vanes. Definitely not a bad thing unless the angle is silly.

 

Nigel

[Snapperpaul]

Don't forget to reroute the 16mm hose, I would also fit the bleed T

Check the rad cap, my last issue was failed rad cap which opened very early pumped out coolant then boiled the rest in short order

[Al Milton]

Dan, Nigel has given loads of pointers to investigate.

Here's a link to my posts about overheating during the summer http://www.rhocar.org/index.php?showtopic=34449&st=0

 

As you can see, the areas to investigate are primarily the same, but take it one step at time.

Car Builder Solutions have a small (1.5litre capacity) expansion tank, which I fitted to my car, simple to do.

Rad caps are the easiest thing to replace (as suggested by Snapperpaul) and I would look at this first.

[Bob Tucker]

Check the hoses are in good condition.

Also avoid any corrugated hoses..they cause turbulence & drag.

[Guest Alan_builder]

Hi again Dan,

 

As I said early on you will get N + 1 replies differing opinions on what is wrong. What is wrong is up to you to find out. My suggestion is not to reinvent the wheel again.

 

ON the subject of slanting radiators like the 2B/04

The reason to slant / tilt the radiator is to cause an greater air pressure drop from one side to the other. As the airway through is the same size you must have created better air contact with the cooling vanes and thus improved cooling. A by product is you can use a larger radiator but 30 degrees is only 1-0.866 =0.134 about 13% (sin 30 =0.866) and then you have the diagonal of the thickness of the radiator to take account of.

 

Problems

I have not seen a post saying blocked radiator or head waterways?

 

2 fans in airflow series, one is sure to stall the other's airflow.

A suck fan is about 10% more efficient than a blow fan, a suck fan used as a push fan (wired -ve to +ve) is about 20% less efficient than a push fan.

 

From the scrap yard.

Peugeot 205 fan (push as it mounts in front of the radiator.

Metro header tank, about 5" diameter pressure cap and 3 or 4 outlets to water system, feet to bottom of system, return from one or more high points and the over flow.

[richardm6994]

back on the subject of slanted rads.....out of interest does anyone know the cut-off point where the angled rad stops becoming benificial as the pressure drop too great?....eg 90-degrees being a vertical rad and 0-degrees being horizontal rad

[Guest mower man]

Even horizontal will work with correct ducting and fans ,it's the old old story of getting air through the rad core perhaps would'nt be to good in slow traffic but would work mowerman

[richardm6994]

I know what you mean, but I'm thinking closer to home...i.e. the nosecone of my RH

[Guest Alan_builder]

back on the subject of slanted rads.....out of interest does anyone know the cut-off point where the angled rad stops becoming benificial as the pressure drop too great?....eg 90-degrees being a vertical rad and 0-degrees being horizontal rad

 

I suspect it is a bit empiric, each type of radiator will have a different angle due to thickness and air hole CSA / W, H and the proximity of surroundings behind, front air way design or lack of and cowling to drive air through the radiator.

From what I have seen in the paddock 30 to 40 degrees seems to be the norm. But how much of that observation is based on science I don't know.

Again one might need to consider frontal area for drag, if there is a pressure drop across the radiator is must be increasing the drag?

 

greavesy7 might be the person who knows best.

[Guest Alan_builder]

I know what you mean, but I'm thinking closer to home...i.e. the nosecone of my RH

 

From the look of your photo it seems your nose cone is blocked off.

 

Which begs the question of Dan "Has the nose cone had its hole cutout made"? Silly but we don't have any pictures.

[richardm6994]

Cheers alan. I know it's different car to car, but generally if you've seen 30-40 degrees that must be a good "rule of thumb"

 

 

 

Again one might need to consider frontal area for drag, if there is a pressure drop across the radiator is must be increasing the drag?

 

I agree, but this did make me chuckle....have you seen my spoiler!! any more drag and it will be going backwards!!

 

 

Personally, I've never had any cooling issues....saying that tho, it might be a different story when the v8 is in, but I'm hoping the new 4-core deep rad helps somewhat! It was just when the angles of rad was mentioned, it caught my attention because it went against what I always thought to be correct! live and learn I think is the appropriate saying here!