The best location for an electric water pump SBC V8 conversion, The best location for an electric water pump SBC V8 conversion Options

[914GT]

That I don't know. The listing says it came off a rear-engine dragster. Maybe they pressurized their system with an air hose for leak testing? I wouldn't think they'd bother with an overflow tank on a dragster.

[Andyrew]

If you're spilling out that much coolant it would seem to me that your system isn't holding pressure. Did you check by pressuring the system (cold) using compressed air and a gauge to see what point your radiator cap opens?

When you're driving the engine is under load and is going to generate more heat. So holding correct pressure (15-17 psi static) is going to be an important factor. Possibly there is some kind of turbulence in the radiator air flow while in motion. I suppose you could see what difference it makes driving around with your hood off as an experiment. I kind of doubt this is the problem though. My guess there's still a pressure problem or maybe still trapped air in the radiator or above the intake manifold somewhere.

You know; the expansion (header) tank is from a VW Passat I got from the breakers yard. It looked in good nick but just in case, I replaced the cap with a new one. Perhaps the tank really is hosed. Any recommendation on the type of tank I should look for?

Just get a new passat expansion tank and try it out. They are only ~$20

[BRAVE_HELIOS]

The most common is probably one similar to this. The small fitting fits a hose going to your overflow tank.
(IMG:http://www.rickwrench.com/images-sounds/filler.jpg)

Renegade makes one that looks nice. This would have to connect into your system with a tee and be mounted high in the engine bay.
(IMG:http://www.914world.com/bbs2/uploads_offsite/www.renegadehybrids.com-2923-1493926666.1.jpg)

I use a modified Dedenbear tank that bolts onto the intake manifold over the thermostat. It has a lot of volume but it can be a little awkward to fill. I just use a long funnel and it's something I only need to do every few years.

Are you sure the cap on your Passat tank is a pressure cap and not simply a fill cap? Is there a pressure rating on it? Having never seen one I don't know anything about that.

Edit: Here's a used Dedenbear tank with an AN fitting. This one is on ebay for $75. These tanks have a section of clear nylon tubing so you can visually check the coolant level in the system. Mine had that but the tubing discolored after a few years and I plugged the holes. To clear the firewall on mine I cut off the hose connection and tapped the hole to thread in a 90 deg fitting.
(IMG:http://www.914world.com/bbs2/uploads_offsite/i216.photobucket.com-2923-1493927705.1.jpg)

My original set up included something very much like the Moroso unit you show (first/top picture). I was told that was not a good way to go so I removed that piece and adapted the VW expansion tank setup. In the picture below, that Moroso piece would have been mounted where the high pressure 'T' from the T-stat to the expansion tank is now located.

[BRAVE_HELIOS]

Someone needs to explain this to me. The tanks in the pictures have two ports (excluding the filler neck where the pressure cap attaches). The VW expansion tank I have has three ports... one from HP side (from T stat), one to LP side before entering water pump and one from expansion tank to overflow (reservoir). How do the two port tanks connect?

[914GT]

On what you call a two-port expansion tank, one side of it is pressurized and connected into the cooling system. The other port is after the pressure cap so that as the coolant expands it goes past the cap and into the non-pressurized overflow tank. These tanks typically connect high in the system and above the thermostat in the intake manifold. This allows any air to get purged out into the overflow tank, then as the engine cools down only coolant is allowed back into the system. So air is automatically purged out during heating and cooling cycles.

I've wondered how the Passat tank is designed. If it connects to both the suction side of the water pump and after the thermostat (hose going to radiator) then what prevents coolant from bypassing the radiator and flowing through the tank? Is this how it is connected in a Passat? Is there something inside the tank that prevents bypassing the radiator?

[Andyrew]

2 port tanks dont constantly purge the trapped air. They simply have a line that holds water, and then another line for overflow. Thats why the 3 port VW tank is optimal and what you see in every modern vehicle.

[BRAVE_HELIOS]

2 port tanks dont constantly purge the trapped air. They simply have a line that holds water, and then another line for overflow. Thats why the 3 port VW tank is optimal and what you see in every modern vehicle.

Well, that's good news. Can you tell me if you believe mine is connected correctly by looking at the pictures? I will try to find a new 3 port tank that takes a standard pressure cap.

[914GT]

I don't know anything about the Passat tank and how it's attached in a factory system. Hopefully there are others on the board who has used it and can advise you about that.

[BRAVE_HELIOS]

I don't know anything about the Passat tank and how it's attached in a factory system. Hopefully there are others on the board who has used it and can advise you about that.

I did it like this... follow the flow!

[914GT]

It looks like it is essentially in parallel with the radiator. The unknown is how much coolant is bypassed through the tank. Obviously it has been designed to work in the Passat 6-cylinder application but is this good in a 914 Chevy V8 conversion where you need as much cooling capacity as possible? I'm not saying this won't work, and maybe it's been used in other 914 conversions successfully. What I am saying is this tank is a different setup then the usual small block Chevy cooling system. To me it would be unnecessary to have the line going back to the suction side of the pump. Maybe you could clamp this line off and see how it affects the cooling?

[Andyrew]

2 port tanks dont constantly purge the trapped air. They simply have a line that holds water, and then another line for overflow. Thats why the 3 port VW tank is optimal and what you see in every modern vehicle.

Well, that's good news. Can you tell me if you believe mine is connected correctly by looking at the pictures? I will try to find a new 3 port tank that takes a standard pressure cap.

Yes it does look correct. The small line is the high HOT side. Should be the highest line in your system.

The big lower line is the return to cold side. Feeding into the water pump works perfect.

[Andyrew]

To me it would be unnecessary to have the line going back to the suction side of the pump. Maybe you could clamp this line off and see how it affects the cooling?

Thats the whole purpose of this expansion tank. Its constantly purging the coolant. Air bubbles and coolant flow into the tank from the small line, then coolant only returns back into the system.

[914GT]

That sound's like a good design especially when the cooling system is together in the same engine compartment. It may not be quite as effective when the radiator is separated from the engine by lines that are low in the cooling system. Also a small V6 is going to have lower cooling demands then a larger displacement V8. I would have to disagree about the 2-port tank not able to purge air. It does this quite effectively as long as it's the highest point in the system, but as with any of them there needs to be a petcock or other arrangement to eliminate trapped air in the radiator on a 914 conversion. Again I'm not saying the Passat tank will not work, or maybe has some advantages over the other tanks, but it's a variation on what is commonly used and it may be having something to do with the overheating problem.

[BRAVE_HELIOS]

That sound's like a good design especially when the cooling system is together in the same engine compartment. It may not be quite as effective when the radiator is separated from the engine by lines that are low in the cooling system. Also a small V6 is going to have lower cooling demands then a larger displacement V8. I would have to disagree about the 2-port tank not able to purge air. It does this quite effectively as long as it's the highest point in the system, but as with any of them there needs to be a petcock or other arrangement to eliminate trapped air in the radiator on a 914 conversion. Again I'm not saying the Passat tank will not work, or maybe has some advantages over the other tanks, but it's a variation on what is commonly used and it may be having something to do with the overheating problem.

With the system I have now, the highest point is where coolant from the high pressure side (just downstream of T-stat) enters the expansion tank. This point (port) sits higher than the T-stat and higher than the top of the radiator. The only part of the system that might sit higher is the heater core. If this is indeed the case; what can I do to ensure the flow and the bleed process works correctly?

[Andyrew]

That sound's like a good design especially when the cooling system is together in the same engine compartment. It may not be quite as effective when the radiator is separated from the engine by lines that are low in the cooling system. Also a small V6 is going to have lower cooling demands then a larger displacement V8. I would have to disagree about the 2-port tank not able to purge air. It does this quite effectively as long as it's the highest point in the system, but as with any of them there needs to be a petcock or other arrangement to eliminate trapped air in the radiator on a 914 conversion. Again I'm not saying the Passat tank will not work, or maybe has some advantages over the other tanks, but it's a variation on what is commonly used and it may be having something to do with the overheating problem.

With the system I have now, the highest point is where coolant from the high pressure side (just downstream of T-stat) enters the expansion tank. This point (port) sits higher than the T-stat and higher than the top of the radiator. The only part of the system that might sit higher is the heater core. If this is indeed the case; what can I do to ensure the flow and the bleed process works correctly?

You need to add some kind of T at your highest point in your engine bay and make that your new expansion tank high line.


For the front end what I do is run a line off the radiator high point with about a foot of hose and hold it straight up. Once that line is pushing pure water I know the radiator is good.

Same for your heater. You need to make a "T" for your heater at the high point, that way you can do the same there. Cap it off when its full.

The system should work the air bubbles out of it naturally with a modern 3 hose expansion, but it could take some time. Thats why I force it out at the beginning. Makes things easy.

[BRAVE_HELIOS]

That sound's like a good design especially when the cooling system is together in the same engine compartment. It may not be quite as effective when the radiator is separated from the engine by lines that are low in the cooling system. Also a small V6 is going to have lower cooling demands then a larger displacement V8. I would have to disagree about the 2-port tank not able to purge air. It does this quite effectively as long as it's the highest point in the system, but as with any of them there needs to be a petcock or other arrangement to eliminate trapped air in the radiator on a 914 conversion. Again I'm not saying the Passat tank will not work, or maybe has some advantages over the other tanks, but it's a variation on what is commonly used and it may be having something to do with the overheating problem.

With the system I have now, the highest point is where coolant from the high pressure side (just downstream of T-stat) enters the expansion tank. This point (port) sits higher than the T-stat and higher than the top of the radiator. The only part of the system that might sit higher is the heater core. If this is indeed the case; what can I do to ensure the flow and the bleed process works correctly?

In the engine bay; There is a T in already in place… that is where the coolant enters the expansion tank. The expansion tank itself is sitting pretty much at the highest point in the engine bay (millimeters from hitting the engine cover).

I like your idea of the hose for the radiator. I can attach a hose on the rad petcock and do the same?

I have a flushing T just inches before the hose enters the heater core and sitting at about the same level. I can use that there too.

[BRAVE_HELIOS]

Was reading a Chevy forum about running hot issues but only when driving (at speed) and someone mentioned that perhaps the pump is spinning in the wrong direction? As in; the incorrect pump was purchased for the application?

My remote pump is mounted on the left side… opposite of what the Renegade manual shows to do. But it seems to me that it should not matter which side the pump is mounted as the rotation of the pump will be the same.

Is this correct? What about might there be different BB Chrysler pumps for different rotations? How would I test this?

This info came from here:
http://www.chevytalk.org/fusionbb/showtopic.php?tid/58316/

[BRAVE_HELIOS]

More reading about this. Other than going with an electric H2O pump; I feel I have exhausted most of my options. I mean this thing should be running as cold as ice right now!

I have a good quality, 2 row aluminum radiator.

I have a very strong fan.

The grill air passage to the rad is so tight, it can keep a license plate sucked right up to the grill.

The expansion tank might be bad and I will replace it.

The whole cooling system has been cleaned out with ThermoCure and citric acid (Prestone) with great care taken not to get radiator clogged.

Now there is the elephant in the room… failed cylinder head gaskets or heads. When I made the swap, I only pulled the bottom of the engine apart and left the top end alone (PO said engine ran strong). What would be the tell-tail signs if the heads were causing the overheat issue? How can I test for this? From what I can see; there is no discernable amounts of oil in the coolant nor coolant in the oil.

Sigh (IMG:style_emoticons/default/sad.gif) … can I remove the heads while the engine is still in the car?

[Andyrew]

More reading about this. Other than going with an electric H2O pump; I feel I have exhausted most of my options. I mean this thing should be running as cold as ice right now!

I have a good quality, 2 row aluminum radiator.

I have a very strong fan.

The grill air passage to the rad is so tight, it can keep a license plate sucked right up to the grill.

The expansion tank might be bad and I will replace it.

The whole cooling system has been cleaned out with ThermoCure and citric acid (Prestone) with great care taken not to get radiator clogged.

Now there is the elephant in the room… failed cylinder head gaskets or heads. When I made the swap, I only pulled the bottom of the engine apart and left the top end alone (PO said engine ran strong). What would be the tell-tail signs if the heads were causing the overheat issue? How can I test for this? From what I can see; there is no discernable amounts of oil in the coolant nor coolant in the oil.

Sigh (IMG:style_emoticons/default/sad.gif) … can I remove the heads while the engine is still in the car?

Probably cant remove the head, its a little tight. You could probably drop the trans and get a little better clearance if you took your dizzy out.

I would leakdown test your engine. If you dont have coolant in the oil and vice versa the only place for the coolant to go apart from external is through the exhaust. Is your exhaust tips white/clean? Pull your plugs and take a borescope to the pistons, are any of them really clean? If so leakdown test is definitely in order.

[Andyrew]

Have you pressure tested your system yet?