After market radiator issues

[svxhunter]

Wow, it's been a long time since I've posted here. I've been playing with WRX's and things, so I've been away for a while. I'm starting another SVX based project, so I guess I'll be back.

Here's my issue: I've got a 5-spd SVX and the radiator blew. I thought I'd be smart and switch to an after-market radiator for additional cooling, since I no longer need the radiator with the built-in tranny cooler. Maybe I wasn't so smart.

The radiator is a Griffin aluminum radiator. It's got nothing to do with Subbies, it was probably made for a Mustang or something like that. But it fit well (after a few minor mods). It is significantly larger than a stock SVX radiator. It has a 16 lb cap on it. I also installed an after market fan, which is running off the stock wiring for the secondary fan. It seems to be functioning OK.

The car is now overheating. I thought the fan might be undersized, or wired into the wrong circuit, but high speed driving does not lower the temperature. The temp continued to climb on the highway (I expected it to fall a bit) I can't figure out why larger capacity radiator with more cool water should mean hotter temps. I'm trying to think through why that might be. I can see decent movement in the radiator when it is hot, indicating to me the the water pump is working.

Any ideas??

[nexus_7]

water pump?

Greg

[ItsPeteReally]

Originally Posted by svxhunter

Any ideas??

The basic engineering facts are:

• The engine generates waste heat (a lot of it).

• The coolant (water) in the cooling system is used as a transfer medium to move this waste heat from the engine to the radiator.

• The radiator extracts heat from the coolant and transfers it to the air flowing through the radiator.

Nothing difficult there.

If the car overheats then one or more of the following can be the only causes:

• The coolant is not being pumped around the cooling system fast enough to keep up with the rate of heat production.

• The radiator cannot dissipate the heat in the coolant at a fast enough rate.

Let's consider the coolant flow first. We know that the standard waterpump was adequate to pump the coolant around the standard cooling system. But perhaps the replacement radiator is more restrictive to the flow of coolant than the original was, or perhaps the hoses are restricting the flow - maybe they have more bends or kinks in them than before.

Then consider the heat dissipation capability of the radiator, this is governed largely by the effective surface area of the radiator and the quantity of air passing over its surface. As you say that the radiator is larger, it seems reasonable to suppose that its effective surface area is greater than the original radiator (but it might not be!). What is possibly of greater concern is the airflow through the radiator. The original radiator is closely matched to the radiator inlet grille of the standard car, they even have foam rubber added to ensure that the air flows through the radiator rather than around it. Not only that but you have fitted a replacement cooling fan (only one?).

To have some idea of what's going on you need to measure the input and output water temperatures, something that's not too easy to do.

If the outflow water temperature is high it indicates that the radiator cannot dissipate the heat fast enough. If the output temperature is low and the inflow temperature high then that tends to indicate that the water is not being pumped around the system fast enough.

The quantity of coolant in the system is largely irrelevant, having another gallon of cold water in the system will only buy you another couple of minutes of time before the system overheats. You need to be able to dump waste heat faster than you are producing it.

[svxhunter]

Yes, I understand all that. But it is very helpful to have it put that clearly.

As you know, measuring the input/ output temps would be pretty tough, so I'll skip that for now, although it would be the most scientific.

Regarding the fan- yes only one at this point. The new radiator was thicker, so stock fans wouldn't fit. I bought a low profile larger diameter fan, which should be clsoe to matching the airflow (sort of).

I've actually made a little progress, so my problem has changed a bit.

I took it out for some highway driving today. The temp was flirting with danger, and I was heading home, when suddenly it dropped pretty quickly. As long as I stayed at highway speed, I was able to keep the temp in the mid range. So, I'm thinking I had a stuck thermostat, or a blockage which blew through.

I'm still dealing with climbing temps at low speed. Pretty sure this would indicate a fan issue. I'll be looking at air flow, fan cfm's, etc, but the SVX issue I need a little help with is the wiring. Anyone know how those 2 original fans were supposed to work? I found 4 wires on each, 3 relays on each, and one fan called primary, and one called secondary. Obviously, one of the wires on each fan is a ground, but why 3 other conducters?

I'm thinking at least one of the original fans should be thermostatically controlled to stay on even after the key is turned off until the engine temp drops. This is what I want, but all the hot lines turn off with the key. If I leave the key in the "on" position, the fan runs until the engine cools and then shuts off. Can I get it to do this with the key "off"?

Additionally, can I get the fan thermostat to kick on at a lower temp?

Thanks for your help.

[shotgunslade]

Paul:

Good to see you back here again. Your struts are now part of my mean track day machine. They really gave me a good start toward a very well-performing track car.

Your overheating problem seems to be similar to a problem I had recently at the track, and then, which followed me home to the street. The consensus seems to be that the EG33 motor has a tendency to capture air in the engine coolant passages, resulting in local overheating, boiling and coolant temperature sensor spikes followed by rapid return to normal. Both the rise and the return were unpredictable and seemed to follow no pattern. The shop determined that my radiator hoses had been improperly installed or inadequately tightened when they were replaced, and that, not only were they leaking, but also, they were aspirating air into the system. As a result, the coolant level indicated in the expansion tank didn't necessarily reflect the true level of coolant in the system, because air was trapped elsewhere. They suggested that I check the coolant level in both the expansion tank and the radiator after the engine had been sitting overnight to see exactly how much coolant was present.

Don't know if this all makes sense, but following this regime, I haven't had any more overheating problems.

[svxhunter]

Glad to hear you are still happy with the work. Am I reading that you went ahead with the 5spd?!

Sounds like youare basically describing air pockets. Makes some sense. Did you do anything to gete the air out of the system other than tighten the hoses?

[TomsSVX]

start the car with the Rad cap off. Let it run 10-15mins to allow the thermostat to open. Once the car is at full running temperature fill the radiator all the way to the top. Put the cap back on and shut the car off. then be sure the overflow tank is filled to the HOT line. This should expell any air from the system.

Tom

[michael]

I found a good solution to this:

Pull the upper coolant hose off the engine block and use it to fill the radiator. Reattach it to the block and fill the engine with coolant. Take the rad. cap off and top off the radiator, then fill the expansion tank to the proper level if needed. I think the air pocket is in the crossover pipe, if I'm not mistaken that is where the coolant temp switch is for the rad fans. Using the coolant hose to fill the block makes the highest point in the cooling system about 6-8 inches higher than normal eliminating the chances of trapped air.

[ItsPeteReally]

Originally Posted by svxhunter

Anyone know how those 2 original fans were supposed to work? I found 4 wires on each, 3 relays on each, and one fan called primary, and one called secondary. Obviously, one of the wires on each fan is a ground, but why 3 other conducters?

I'm thinking at least one of the original fans should be thermostatically controlled to stay on even after the key is turned off until the engine temp drops. This is what I want, but all the hot lines turn off with the key. If I leave the key in the "on" position, the fan runs until the engine cools and then shuts off. Can I get it to do this with the key "off"?

Additionally, can I get the fan thermostat to kick on at a lower temp?

Thanks for your help.

I've just had a look at the wiring diagram .... and ..... all I can say is, I wish that things were that simple!

First the simple bit, the reason that the fan motors have four connections is that they have two sets of windings, one set (BLK & BLK/YEL wires) powered through Fan Relay 1 and the other set powered through various combinations of --- wait for it, Fan Relay 2, Fan Relay 3, Fan Relay 4 and Fan Relay 5!

Now it starts getting complicated!

This is where I start tip-toeing quietly away.

(Voice getting fainter now as I disappear) all of this rat's nest is driven by contacts D3 and D17 of the MPI control module (whatever that is).

Frankly mate, you are on your own now!

[ItsPeteReally]

OK, I'm back!

According to the wiring diagram the fan fuses are powered up all the time, regardless of the ignition switch position. It's the mystic MPI controller that runs the fans.

The reason that the fans do not run all the time is possibly that it would serve no practical purpose. Unless there was some thermo-syphoning action, which continued to circulate water around the system even when the water pump was not running, it would not cool the engine. Certainly the fans would cool down the water in the radiator - but what would be the point of that?

Why would you want to cool the engine anyway? The purpose of the cooling system is to keep the engine running at the optimum operating temperature which is hot, but not too hot.

The easiest way out of your problems has to be to return the system to stock ( I know you don't want to hear this!).

[svxhunter]

Thanks a lot.

There is no turning back. This car is so far from stock, it will never return!

"Hot, but not too hot"- right, but I am overheating. That's too hot.

The reason to have the fans continue to run for a short while after the ignition is switched off, is to help prevent it from getting too hot. Alll cars temperature climbs immediately after turning off the key. Most electric fans remain on to assist in pulling a limited amount of ambient air into the engine bay of a non-running vehicle.

I saw the same mess in the wiring diagrams. That's why I asked you guys!

[ItsPeteReally]

Originally Posted by svxhunter

"Hot, but not too hot"- right, but I am overheating. That's too hot.

So deal with that problem. I am not trying to be deliberately difficult, but worrying about cooling the thing down after it has overheated is just ignoring the root cause of your problem. Yes, I am aware of the possibility of heat soaking into the non-circulating coolant after the engine is turned off, all cars suffer from it to a greater or lesser extent, and if the coolant is not already boiling, then this should not be a cause of great concern. If this is a concern to you, then you are going to have to invent your own solution.

Without measuring the radiator inlet and outlet temperatures we are always going to be working in the dark, but if we assume, as you seem to be doing, that the cause of the problem is lack of airflow through the radiator at low speeds then it seems to me that the replacement fan is either not moving enough air through the radiator, or that the fan does not cover enough surface area of the radiator to be effective (maybe even both ).

I presume that the replacement fan has a shroud around it, closely coupled to the radiator, and that the fan is turning in the correct direction to 'suck' air through the radiator. Sorry if I appear to be stating the obvious, but we need to suck air through the radiator core and not merely gather air from somewhere in the general direction of it.

The fan(s) are really there to deal with cooling the engine when stationary or crawling in heavy traffic when the engine is not developing (or wasting) much power. Even at low speeds I would expect a fair degree of ram-air from the grille to be flowing through the radiator (rather than taking an easier path around the radiator). It might be that all you need to do is to ensure that all the air passing through the radiator grille actually passes through the radiator.

Once again, I leave you on your own. Best of luck!

[svxfiles]

Hunter, I also have a Griffith in my Claret and there are pictures in my locker.
Mine needed two fans to keep the big rad cool.
Like yours it was fine on the highway, and as I slowed down the temp would climb.
I installed twin small thin fans, and hooked them directly to the alternator hot (hot all the time) and used a temperature probe that was adjustable so I could keep the car cool even in trafic.
Go to svxfiles radiator in my locker.

[svxhunter]

I'm understanding all that.

My question is not about the fundamental concepts of engine cooling. My question is specifically about the SVX:

Does anyone know anything about the way in which the circuitry functions? What are the relays designed to do, why are there several, how do the temp thermostat (s) function, what controls the circuitry, and what it is designed to do. Without a basic understanding of these questions, it won't be possible to problem solve the wiring.

There are 8 wires in the front of the car. It only takes 2 to run a fan.

If I do have the answer to any of this, it would be helpful to solving part of my problem (although I realize I still need to deal with flow, CFM's, surface area, etc.)

I realize I have several issues happening at once. I can handle the fundamentals. I need some SVX help. Can anyone help?

[svxhunter]

Thanks SVXFiles. That's helpful.