Need advice on cooling system

I have had my replica on the road for a few years, and have not been able to solve a slight overheating problem when the car is stationary for a few minutes. I read a thread some months back about someone who ran a vent from the top of the radiator to the back of the car into the cooling system, which had a pretty effective outcome. I would like to know someone I could exchange emails to understand where the vent line was plumbed into the cooling system, as well as a couple of other related questions. Would really appreciate any help on this one.

Thanks-Jack

Jack,

one very common problem with rear engine cooling systems is STEAM.

If the cooling system builds steam,it will develop air pockets and seriously hinder circualtion.

Here are some basic tips:

#1:make sure that your filler cap is at the highest point in the cooling system.

#2: put an "air bleed" on the highest point possible on the radiator.

Run a hose from this air bleed to the surge tank. This will allow trapped air to "bleed" to the top of the system, which will help insure good flow of coolant.

#3 STEAM- air bubbles are usually cause by steam in the system ( or exhaust gasses entering the cooling system via leaky head gaskets)

One way to control steam is by adding a restrictor at the entrance of the radiator.
A washer with a 3/4 inch ID hole works for most V8 engines.

The reason for doing this is to allow the water pump to "pressurize" the line going into the radiator, so that superheated coolant will not "steam" until it actually reaches the radiator,,,where it can condense back into liquid.

#4 airflow,the key to airflow through the radiator is not to have a huge hole in front of it,,,,,but rather to have good ducting which will not allow air to bypass/or bleed around the radiator. Aluminum, rubber, etc can be used to properly duct your radiator.
Also, the area behind the radiator is also critical for good airflow.

For times when you are not moving, you want a good pair of electric fans mounted very close to the rad fins. Most elec fans are designed to be within millimeters of the radiator in order to perform properly.

I find it is best to have any temp sensor for the fans mounted on the cylinder head for accurate activation of the fans.

#5 thermostats, some will tell you that they run without a thermostat. I do not agree with this philosophy. You need a thermostat to control the system, and also a high quality rad cap. A higher pressure read cap will also raise the boiling point of a cooling system.
One inexpensive car which can be sourced is a 22psi unit for a mercedes 190 or 300e.
These are less expensive than buying so called "racing caps" and have a 22 psi rating.

Oh, my coolant of choice is distilled water and redline "water wetter, with pump lubricant".

Of course this offers no freezing protection, so that must be considered for those in colder climates.

I hope this helps. Alain

Alain
I agree with everything you said execpt thermostat. In my Lola and MK-IV I found a thermostat caused air to form. I took them out and used a restictor plate in place of the thermostat and they cool fine.
Best
Jim

[ March 21, 2003: Message edited by: MK -IV J6 ]

Jack,

Contact Mark Clapp on the forum. He had a new radiator built for his GT40 with extra cooling area added. He could give you the details. It solved his overheating very well, he said.

Have fun!

John

You can remove the thermostat, however you could also use something like a Davies Craig electric water pump and controller. That way the pump acts like the thermostat whilst the engine warms up, as it will not pump until a certain temperature. The best way for this to work is to remove the impelor shaft from the water pump, thus removing resistance for the other pump and the water in general. The pump only takes a maximum 7.5 A and can flow between 20-92L/min and also only weighs in at 900 grams. This is what I am planning to do when I get to that stage on my car. The person I met last year who had done this found he had a better control over the temperature over all then prior to the fitting.

Brett

Before using a high pressure radiator cap, check with the manufacturer of the radiator to see the maximum pressure that it was designed to take. I was advised by someone to use a 22psi cap on my system and burst the radiator. The manufacturer would not repair it under warranty. I now run a 15psi with no problem. Be warned.

Brian.

Brian does make a good point to check with the manufacturer about their recommendations for the pressure the radiator is designed to withstand.

It is interesting to hear you lost a radiator using a 22psi cap. I'd be suspect of the consturction of that radiator, myself.


Many current OEM manufacturers have been using higher pressure systems for years now,,,,in conjunction with modern aluminum core radiators. These OEM radiators are constructed with plastic tanks, and use a simple O-ring to seal the tank to the core, with a mere crim at the core. (not exactly what I would call a stout construction technique.) These radiators usuually last well over 100k miles. What brings them to their death is that they will usually crack right at the neck where the hose clamp is connected.

This is due to the plastic beoming brittle from x amount of heat cycles, and the acid content in the coolant as it ages & the PH leve rises. Also the plastic tanks expand & contract at a different rate then the steel clamp on the hose, which aids in the eventual failure.
This is one of the reasons why most manufacturers stress coolant changes every 24 months.

The electric water pump systems such as the Davies-Craig, sound like a good solution on paper,,,,,,,,but I have yet to try one myself, therefore have no real world experience with it. (yet)

We've been using a Davies-Craig pump in a well-used car for about a year. No problems at all, and the temperature never goes above 200F, even at idle.

Having problems at idle can come from two places: Low pump flow and low air flow from the radiator fans. That's why the electric pump works well - it can have maximum flow at idle. Because there tends to be quite a bit of plumbing between the engine and radiator, I suspect that a mechanical water pump is marginal at idle. It's a centrifugal pump, after all - their flow is roughly proportional to the square of the speed.

Another factor that might help is using a vacuum-advance distributor. It makes the engine more efficient at idle.

Does the Davies-Craig controller act in an on/off fashion or does it adjust flow speed continuously to maintain temp.

All-Many thanks for the quick and comprehensive responses. I have followed most of the suggestions such as inlet location, fans, ducting, etc. I will be experimenting with thermostat versus restrictor plate, as well as a restrictor in the radiator inlet. I am running a stock water pump, and may also try a high-volume aluminum pump. Any recommendations as to the most effective aluminum pump? I am running a 351 Cleveland.

Thanks again-Jack

Jack
Two things that I did in my MK-IV made a big difference. Using pulleys I overspeeded the water pump and alternator. It's idle that gets you. With overspeeded Water and amps you keep up the flo and keep the fans going.
The other trick is to "Bank" cooling. If you know you're coming to traffic switch on your fans before you exit the highway don't wait until temp starts to rise. BTW I still rev my 427 to 7000 and have had no problems with overspeeding the water and amps.
Best
Jim

One very good alum. pump is a edelbrock Victor series. They come in both left and right inlet and normal or reverce flow. Use a larger pulley than say a 5.0 mustang. Also the fill cap and VENT LINE to the system must be as high in the car as possible. Mine clears the rear bodywork above the vertical rear window by about a 1/4". The non themostat with a simple hole in a round piece of alum works pretty good. Start with a 3/4" whole and work towards a engine temp 160-175. The real GT40's used a vent line from the top of the hot side of the radiator back to the surge tank. Thats about it except bleeding the air out. Warm up the car, VENT OFF PRESURE. Jack up the front of the car as high as you can. Try to get the top of the raditor the highest point in the system. Then finish fill the system through the water temp sensor bung in the intake manifold. Make up a long hose with fitting to attach to this point with a funnel at the other end. Hold the funnel end a foot of so above the car, Higher than the entire system. and finish filling the system from here. When the bleed screws on the radiator flow water all the air is out. All this stuff together should work. If you still overheat check for blown head gasket, ETC. Good luck!

[ March 22, 2003: Message edited by: Howard Jones ]

Gary,
The set-up can be done in two ways:
1/ You just by the pump. This will give you continuousflow and probably keep you engine a little cool.
2/ You can buy the Water Pump controller, that I forgot to mention above. This will allow you to set the flow etc.

Anyway go to http://www.daviescraig.com.au/ for more info.

Brett

Robert Logan,
I'll have to give you props on this one. I'm not as schooled and experenced with cars as others on this forum but they have come up with great tricks and techniques to avoid overheating. With your cars all I remember is filling it up with fuild and hitting the key. As long as I've been around Hershal's car I've never seen a drop of fluid come out of the cooling system. Even when it was 110 out. Once again you've done your homework well. I hope and assume I will be as lucky with mine. We'll find out in a few weeks. Hopefully, but if not thank you to evryone for all the tricks and advice.
John

Jack,

How could I not respond to someone who lives in a place so close to my heart (Dublin) even if it has been displaced by thousands of miles.

Aquick joke for St. Pats Day last week :

Why is Ireland one of the worlds richest countries ?

Because it's capital is always Dublin (Doubling).

On to more serious matters.

The overheating problem is very evident in a lot of cars and even in the UK where it rarely shines. There are many in the various clubs who realy worry about taking their cars into the Europe (mainland) because of this reason. I was always afixed at the temperature guage just in case.

I supose the first thing that I would do is check the gauges are working correctly, remember that they are usually Smiths which look great but are not that accurate and definately not consistant. This can be done using a lazer thermometer which is used in the aircraft world amongst other industries.
While the area beside the thermostat is being checked other areas can also be checked. The radiator (inlet and outlet), the rear of the heads and the inlet and outlet from the engine. Now at least you will have a reference set of data to assertain if what you are doing improves or not the efficiency of the cooling system. You also have a good indication of what is going on in the system and this data will indicate the presence of steam in the back of the heads or in the input side of the radiator.

The cooling system is a closed system designed to maintain temperature to a pre determined level for a particular engine. The size and efficiency (read hp) of the engine determines the sizes of all components. Our system is excellent up to 40 deg with cars producing in the mid 400 hp. Above this static loads with A/C on ocassionally cause problems but these can be checked as our fans are controlled by the engine computer and they can be cut in earlier by as little as half a degree.

Our system was specially designed for our cars but the bleed from the radiator to the coolant bottle and the rear of head bypasses have been a major reason why our cars behave as they do.

Best of luck,

Robert

Jack,

Drawing on the experience with my GTD (and many of the other GTDs that compete each season in the UK with race prepared engines), most of us have found that the only guaranteed way of curing the overheating problem is to switch from the standard radiator to a high efficiency aluminium radiator.

This cured the problem immediately with my car, and she will run on the circuit all day at 90 degrees without the fans ever cutting in. If I sit in traffic, as soon as the fans cut in, the temperature drops right back to 90 degrees within a minute or two.

The other good thing about aluminium radiators is the weight saving - I couldn't believe how much lighter they are! The bad news is that they are not cheap (£300 to £400 dependent on manufacturer).

Martin

There is a guy here in the US (Don't remember exactly where, but I can get it from Farhad Faili - he changed his in a GTD) who makes Ali radiators to your specifications for just under $300.00 US (shipping in the US was included last year).
If there is any interest I'll dig up his business data.

I work with a guy who races a charger with a 440 running 8 second 1/4 miles. He also drives the car occasionaly on the street. The other day i see him order a radiater for a vw scirrocco. He tells me it is for his car and that it works awsome, no overheating and a new one just cost him $75 cdn. I am hugely sceptical but looking at the rad it is pretty big and all aluminum. Might be worth a try at that price.