I highly recommend the LCD controller for the davies craig pump. I LOVE mine.

The water pump runs on its pulse setting pretty much the entire time because its so efficient. It actually rarely gets up to temp doing that. Which I guess I should have guessed since I bought the v8 pump for my 1.8T..

So why are you going from this pump to the Jegs unit? Depending on what you say... I may be interested in your Davies pump!

Basically It will be less reworking of my system and cost.
I already have the Renagade pump and the hoses connected.
With the Davies pump I will need to change the hose arrangement and add a Dedenbear water log, fittings ect.

I may regret selling the davies system but who knows?
David

I understand... I would be in the same situation. Well, let me know how it goes with the Jegs unit because I might very well be the next test case for the same!

An update... Today, I had a chance to drive the car after removing the Prestone flushing fluid and bleeding the system the best I could. I drove for around 3 miles before the temp crept up past 200. This is with the temp controller set for the fan to come on at 180. Ambient air temp was around 72 degrees and I got it up to 70 as a short burst and around 50 most of the rest of the way. This trek was actually better than before where 3 miles would have been a miracle. Was it all the flushing? I have read that a good flushing takes a long time and with many attempts. IDK but obviously, this is still not enough.

When I did get it home, the temp was around 200. I shut it down and opened the trunk where I noticed the overflow tank was full and in a matter of a few moments, water started coming out of the overflow hose of the tank and onto the ground. Mind you when I started the trip, the overflow tank had water in it (that was post bleeding and idling in the garage for a long period of time). I went back to the car after 20 minutes or so and the system had sucked ALL the water from the overflow tank back in... and probably sucked in air at that point too.

I did notice something though... now the car can sit idling in the garage for an hour or longer and never go past 180. It's not until I take it for a drive will the temperature increase.

Did I not read somewhere that when this occurs, it is relatively clear that it is more a function of a defect in air flow through the rad and/or how the hot air expels from the front trunk area and not from deficient water pump flow?

I am trying to come up with the next logical part of the system to address.

Any one have insight to the running hot when driving versus at idle issue... please :-) .

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?

The most common is probably one similar to this. The small fitting fits a hose going to your overflow tank.


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.


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.

Why would there be a quick connect air fitting on the Dedenbear tank overflow tube? Good-looking parts.

Bob B

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.

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

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.

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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?

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?

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.

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!

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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?

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.

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.

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.

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.

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/

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 … 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.

Have you pressure tested your system yet?

I have yet to perform a compression test oor leak down test.

He's saying pressure test the cooling system, it's a pump that you can use to check to see if the system is holding pressure--they're fairly effective at identifying most leaks in a cooling system. The vacuum tool that I showed you can also be used the same way, if you vacuum the system and the vacuum doesn't hold in the green zone then you've got a leak somewhere--potentially headgasket. I have both though, as the pressure tester is a little better at pinpointing leaks, but both will indicate an issue that requires attention.

You can also perform a combustion gas check on the coolant to see if you've got a leak from the combustion chamber.

Running hot at speed can be a lot of things, insufficient airflow, clogged or poorly sized radiator, trapped air, low coolant/insufficient water flow, tuning issues, head gasket, etc.

I'll say again, you should make sure that what you have is working properly before you throw more parts at things, and part of that is making sure the system is properly bled. The vacuum tools are amazing, and make coolant filling so easy and trouble free

You where saying decent temps of 180-200. You then said creeping up past 200.
Does it stop there or did you just stop. My V8 914 in 78 went to 200 a lot. I also owned a 85 corvette in 94 that the heat went past 220 and I just did not want to stop and I was in the desert and had 2 miles to go and I said screw it and overheated it and blew a head gasket. No water got in the Eng. One of my guys put a new head gasket in it and it was fine.
So how hot has your car got?

Bob B

I rented a cooling system pressure tester from O'Reily's a while back. The kit did not have the correct adapter for a VW expansion tank so I had to fabricate my own. My son had to hold it in place while I pressurized the system. I used it mostly to purge air from the radiator petcock and not to test holding pressure.

Today; I took a ride to my local breakers yard and specifically looked for an expansion tank that was from a V8 car and that had the standard twist/lock pressure cap. Found one out of a Crown Vic/Grand Marquis that fit the bill. Took it home and made a temporary mount to test it. Right away. I noticed that where previously with the VW expansion tank, coolant would eventually flow out of the expansion tank and into overflow tank then would begin to fill up the overflow tank until it overflowed to the ground. This did not occur with the Ford unit. The overflow tank level did not have any discernible change in coolant level. Good sign, I hope.

Although I could not find anyone around here that rents out leak down testers, I will go to the FLAPS and rent out the pressure tester again.

If I understand this tool correctly; it will show me external leaks fairly immediately and will let me know of internal leaks by whether the pressure drops over X amount of time. Is this the correct way to diagnose with the pressure tester?

Hey Bob,

Quite the story with the Vette!

I do not think my car has ever overheated (with the engine in the 914 anyway... previous owner... possibly).

The gauge continues to read even after the engine is shut down. I have seen the temp creep up past 220 like this. I have also seen the coolant bubble (boil?) in the overflow tank once or twice... cannot recall what the temp was reading at the time but I am sure it was up there.

I am going to rent a pressure tester tomorrow and see what happens. I would like to rent a leak down tester but it seems that no one around here rents one!

Update... I went and rented a pressure tester. When I got home, I removed the cap from the Crown Vic expansion tank and immediately noticed that the expansion was still full of coolant. I had never experienced that with the Passat expansion tank... that tank was always half empty... no matter how many times I filled it before driving... always.

I tested the 16 PSI cap and it checked out. Next, I pressurized the system to 16 PSI and even though it dropped a hair, it has been holding in the 15-16 PSI range on the gauge for over 10 minutes now. No external leaks and hopefully no internal leaks either. Good signs I think!

I read another test I can perform with the pressure tester is to remove all the spark plugs, pressurize the cooling system, then crank the engine to see if any coolant comes out of the spark plug holes.

Another is the exhaust gas tester for cooling systems.

It seems no one around here rents leak down tester or exhaust gas testers... it would suck to have to buy these things for one time testing.

Are the observations, tests and subsequent results performed so far enough to come to the determination that all is well with my cylinders and gaskets? I reckon it would be easy enough to perform the other test I mentioned with the pressure tester and removing the spark plugs... if I have to.

BTW... thanks for all your help!

More good news... I rented a block tester/combustion leak tester; followed the directions and pumped for more than 2 minutes (instructions say 2 minutes) and the test fluid did not turn yellow... no combustion gasses in the coolant! What a relief! I will try it one more time before I return the kit. The photos shown are after I had pumped for over 2 minutes.

Now I can proceed!

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Temp creep isn't uncommon, as the heat rises up to the temp sender. Coolant bubbling is common when there is air still trapped in the system.


This doesn't surprise me. My engine in it's original car has a 9 quart cooling system. In my 914 it's 12 with the 20ft of 1 1/4" hose. Since the Passat tank was designed for a little 2.0 or 3.0 engine with 1-2ft hoses it's likely expanding beyond capacity.

I can completely understand this if it weren't for the examples of other 914 V8 owners that seem to do all right with a small expansion tank... at least I think they are expansion tanks... little tanks with pressure caps attached.

I now need to make a permanent mount for the tank and take it out for a drive. Reckon I should also remove the restriction washer inserted in the radiator inlet too.

You talking about this? It's a filler / air catcher (swirl can). Connects to the overflow bottle. Mine is on the output side of the engine.



Replaced it with this when I replaced hoses & radiator.

Finally getting to work on the car. Work travel is killing me.
Have to machine the Renegade pump housing to allow the Jegs unit to fit.
The step on the jegs pump is a little over .500. I machined the housing .600 and enlarged the dia about.030.
Made a mounting bracket and in process of wiring the relays. Will have it come on with Ign. and also tied to the fan switch on the radiator to run after engine is off untill temp comes down.
test running the pump pushes a lot of air out of the system and should help bleeding ?

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Hi David,

Sorry I haven't called... but I will!

Man I'm rooting for ya... I really hope this works!

Out of curiosity; once you start machining the housing to accept the Jegs pump and for whatever the reason, you decide later to go back to a mechanical setup; will the same housing still work at that point?

Sure , No problem.
I dont think there will be an issue as the bolts help to align it.
David

Hey all,

Happy Memorial Day!

I think the car has running much cooler since incorporating the expansion tank out of a v8 Crown Vic. I have taken it for a short drive or two (around 3 miles) with the new setup and it never got past 200. Mind you this is with no T-stat, no rad restrictor washer and straight water for cooling. Fan is configured to come on at 160.

Today; I decided to remove the hood and take it for another drive; this time around 5 miles. Bright sunny day and around 83 degrees out, mixed driving and reaching speeds up to 70 then mostly 40-50. I must say; driving around without a hood garners many looks and thumbs up!

I think removing the hood helped, at least a bit. After my 5 mile loop, the temp was around 190 when I pulled int the garage.

I guess I am having a hard time figuring out what is acceptable for a running temp. I mean if I can keep the temp at 200 or less, even with no t-stat and the fan coming on at 160; I would be happy. If at this time, my setup still has the potential of overheating, what should I do next? Four row radiator? Electric W/P? Both?

See the attached pictures... and back to removing the hood. Like I said; I think it did help in keeping the temp a bit lower but I do not want to drive around with no hood all the time! What about drilling large holes on the front trunk floor to allow more air to escape. Is that feasible? Will it take away from structure rigidity?

Also; if you take a closer look at the picture of the grille versus the length of the radiator, you will notice that the radiator is longer that the grill opening. It is completely sealed and ducted but I wonder if the opening should be larger. I think tomorrow, I will remove the bumper and take it for a drive and see if makes any difference. Stay tuned for more!

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Funny you should say Crown Vic. I worked on a Grand Marquis the other day and thought of you

It's expansion tank is just a tank with 2 chambers. Feeds from the little hose attached to the top of the rad and returns thru the Tee on the lower return hose/eng intake.

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190 is a fine temp for a SBC. The 10 degree drop could be air getting purged with the overnight cool down. You've got 3x the airflow I have and my engine runs at ideal temp so I doubt that's a problem.

Lol! Mine looks very much like the one you show except it has the older style twist pressure cap.

I have 3x the airflow because I removed the hood or even with the hood installed? You do not think that drilling large holes in the floor will help with cooling? What type of rad do you have... a 4 core? How about your W/P? Electric or mechanical. Why does your run so cool?

hood installed.


Stock mechanical.


VW Corrado with 2 Spal fans to replicate the 2 speed stock fan, back when I first did the conv in 2001. Toyota Celica with stock Celica fans now. I'd say 2 core single pass.


Not a SBC



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That's it. 2 ugly floor holes from the AC, 5 plugs removed, and 2 holes with deflectors from the horn grilles. The air only expands 20% after heated, NOT 200% as is being sold.

Fun fact. My 180F thermostat starts to open at 180F and reaches full open (~3/8") at 203F. At 203F low speed fan is triggered, at 212F high speed fan is triggered. High speed is rarely triggered but in slow traffic. All controlled by the stock ECU.

Wow... hardly holey at all!

I wonder; I notice that your rad is angled back versus mine being angled forward. Does that make a difference in air flow? Coolant flow?

It makes sense in his case since the airflow needs to go down. Yours should be fine as is.


All signs on your setup point to the fact that it should work.

It was such a nice day; I decided to remove my bumper (as if I didn't have anything better to do!).

I have not taken it out for a drive yet to test cooling but I did want to show you all a a couple of things like the opening in the bulkhead and the rather large (for the Chalon bumper) ducting from the bumper to the bulkhead. Remember... I got that sucker so sealed that the fan will suck in a license plate to the grille!

Do you think the bulkhead opening is large enough? I can probably remove those two rubber plugs to add a bit more to the air flow. What about the grille opening on the bumper... it is around 21 inch by 5 inch. Is it a sufficient size for the cooling?

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