Closed cooling system. Advantages and disadvantages?

[First opel 1981]

It has long been my feelings that there are 3 main reasons Opel 1.9 engines die.

1) Cracked head
2) Toasted bearing
3) Timing chain slop skips a tooth

I am not worried about #2 and #3 but the cracked head issue got me to thinking.
Why didn't the 1.9 come with a closed system? With an open system you have to keep topping off the radiator which most younger people will forget. I know I did with my first one. When adding coolant to the hot head it has the best chance of cracking, even if the engine is running.
A closed system makes the most sense, right?

What are the advantages and disadvantages to converting a stock 1.9 to a closed system?

Specs would be using the Stant SP-21, 14psi radiator cap (as suggested in another thread) and a minimum 2 qt overflow bottle.

Thanks for the input.

[RallyBob]

From my experience the biggest reason the Opel heads crack is twofold. Later heads (1972-1975) crack primarily because they have induction hardened seats, and are VERY brittle. However all the heads are prone to cracking because of a tendency to run extremely hot at cylinders #2 and #3.

The reasons they run hot include, but are not limited to:

*Much higher exhaust flow at #2 and #3 exhaust ports, which leads to overscavenging, pulling still-burning air/fuel into the exhaust ports.
*High exhaust flow in general compared to the intake flow, again causing overscavenging.
*Exhaust manifold being 'open' and shared at cylinders #2 and #3. Individual tubes would run cooler.
*No coolant passages or intake ports between exhaust ports #2 and #3. So they run hotter through convection as well, no incoming air/fuel to cool the ports, and no coolant to cool the ports.

As as example, the center exhaust ports normally run about 200°-250° hotter EGT's than #1 and #4. And those outer ports still run hot...about 1400-1450°. Terminal for many other brands of engines!

Balancing the exhaust flow, increasing the intake flow, and adding two extra 3/8" holes in the head gasket near the center exhaust ports can drop those temps by up to 300°. I'm not saying the heads can't crack at this point, but the chances are severely lessened!

HTH,
Bob

[First opel 1981]

Modifying the head gasket was something I was going to explore but now I don't have to. Thank you.

Now, what are your feelings on the closed system?

[Dennis Texas]

Originally Posted by First opel 1981 Now, what are your feelings on the closed system?

If you mean a pressure cap and overflow is captured in a container and when it cools off it sucks the water back into the radiator, then I have one on my 73, works great, just don't put the container in front of the radiator it make make it less able to cool by blocking portion of the fins.

[First opel 1981]

Yes, that is exactly what I was asking about.

Thanks for your input.
I saw a picture of a reservoir bolted to the left of the radiator and looked like that was a perfect spot to mount one.

[tekenaar]

Originally Posted by First opel 1981 Modifying the head gasket was something I was going to explore but now I don't have to. Thank you. Now, what are your feelings on the closed system?

. . . do, and have done, that routinely since my first GT in 1976 . . . mostly with scavenged plastic tanks from 'used-car emporiums' . . . er, junk yards . . . my personal contribution to recycling car parts!

[Motor Mouth]

Originally Posted by tekenaar

Slightly off topic, but what's that you've got going over the top of the rocker cover?

As for closed loop systems, over in europe many of the owners go for the fully pressurised systems found in something like a Monza/Senator or Carlton engine bay, here's a pic from my old Monza GS/E, you can see the radiator is closed and is top-up tank is on the Right Hand side of the engine bay....could be the way to go?

[RallyBob]

Originally Posted by Motor Mouth As for closed loop systems, over in europe many of the owners go for the fully pressurised systems found in something like a Monza/Senator or Carlton engine bay, here's a pic from my old Monza GS/E, you can see the radiator is closed and is top-up tank is on the Right Hand side of the engine bay....could be the way to go?

Yup, that's a better way to go. If the radiator is not designed from the get-go for this application (without a cap at all), then you need to change your OEM Opel radiator cap to a returnable-style cap.

And make sure the remote reservoir (also called a surge tank) is mounted higher than the rest of the cooling system to prevent air pockets from forming. Any air pockets will virtually guarantee overheating!

[First opel 1981]

Originally Posted by RallyBob And make sure the remote reservoir (also called a surge tank) is mounted higher than the rest of the cooling system to prevent air pockets from forming. Any air pockets will virtually guarantee overheating!

Higher than the rest of the cooling system? Why is that?
On my Mustang and my Thinderbird (the only two cars I can look at right now) the recovery tanks are located below the radiator cap level.

Why would an added recovery tank need to be higher on an Opel?

Just curious.

[RallyBob]

Originally Posted by First opel 1981 Higher than the rest of the cooling system? Why is that? On my Mustang and my Thinderbird (the only two cars I can look at right now) the recovery tanks are located below the radiator cap level. Why would an added recovery tank need to be higher on an Opel? Just curious.

With a returnless system it doesn't matter, but with a full recirculating system, there needs to be a way for air pockets to rise to the highest point. If the tank is below the radiator, then the radiator will likely have an air pocket. Or the cylinder head, or the heater core, or whatever is higher!

On some new cars this is an issue, Nissan 350Z's have the heater core as the highest point, and need about 6 hours to bleed the system of air or they will overheat every time! Ask any Nissan technician....

[First opel 1981]

Ah, you are speaking of the high end system, not the "add a cap and add a tank for $20" upgrade.

Now I understand.

I am not ashamed to say I am looking for cheap cooling system insurance. I'm not building a racing machine but rather something that my son can drive and turn heads in. It's his money and, as most know, 19yo wages aren't quite perfect for high end upgrades.

[RallyBob]

Originally Posted by First opel 1981 Ah, you are speaking of the high end system, not the "add a cap and add a tank for $20" upgrade. Now I understand. I am not ashamed to say I am looking for cheap cooling system insurance. I'm not building a racing machine but rather something that my son can drive and turn heads in. It's his money and, as most know, 19yo wages aren't quite perfect for high end upgrades.

Doesn't need to be high-end really, you can use a surge tank from a junkyard car, then convert the radiator. VW radiators and surge tanks (or WRX Subaru surge tanks) work well for this.

[First opel 1981]

I will keep those in mind. Not that I'm oppsed to going it that way or anything but I think the simple verflow system will suffice.

I did see a nice setup at OGTS for something like $600. (or was that a dream?)

[newman27]

Originally Posted by First opel 1981 Ah, you are speaking of the high end system, not the "add a cap and add a tank for $20" upgrade...

I'm liking this idea because it bugs me that on the GT you can't really tell what the coolant level is due to the filler neck opening being stuck out away from the radiator itself (i.e., you can't look straight down into the radiator). Some coolant is always laying there in the filler neck it seems but that doesn't mean you are "full up".

[tekenaar]

Originally Posted by Motor Mouth Slightly off topic, but what's that you've got going over the top of the rocker cover? As for closed loop systems, . . .

. . . that's a forced air injector cooling system with blower motor mounted underneath on the GT front suspension cross frame from a Datsun 280Z FI engine . . . junk-yard! . . . some more detail pics . . .

[markandson]

Originally Posted by First opel 1981 I will keep those in mind. Not that I'm oppsed to going it that way or anything but I think the simple verflow system will suffice. I did see a nice setup at OGTS for something like $600. (or was that a dream?)

Not a dream for me, this is it.

[CDN OpelNut]

Originally Posted by markandson Not a dream for me, this is it.

Not to steal this thread....... I don't know what the h*ll half of the stuff under that hood does, but boy, it sure is perdy!

[newman27]

Otto - can you recall what type of vehicle the overflow container in this picture came from?

Thanks!

Matt

[First opel 1981]

It appears that there is no downside to converting to a closed (reservoir overfow) system.

For the price of conversion, I can't think of better cooling system insurance.

[newman27]

For future reference, here is a thread specifically on the over-flow bottle. I've decided to go with the polished stainless steel bottle that "bosco" mentions. They are available on eBay. BTW, that set-up that "MrGing / Ging" came up with is pretty cool!

I have been trying to find a 14 PSI Stant cap and can only find 13 PSI caps locally. The SP-21 part number isn't registering anywhere either. FWIW, The FSM says to use a cap that is rated 13.2 - 15.2 PSI. That said, doesn't the single number rating on the cap translate to a higher SAE range like the FSM is quoting?

[First opel 1981]

Hey, thanks for that link.
I looked all over for the topic before I posted because I had heard people don't like answering questions twice.

That other link shows quite a few options for overflow bottles.

[officertyo]

The pictures and the talk of overflow bottles have me realizing something very funny. The PO of my car and me in turn, (because i did'nt know any better) have been using the washer fluid bottle as a coolant overflow bottle.

[West Coast GT]

Check out the plastic reservoirs found in Saturns. There are a ka-zillion of them available, their reservoirs are pressurized rather than "open", and they come with pressure-relief style caps.

An advantage of the plastic tanks over metal is the ability to quickly, and visually, confirm the system has a proper coolant level.

IMHO it would be dicey at best to grab an over-flow tank from an open system style car and use it in a pressurized system.

[First opel 1981]

Originally Posted by officertyo The pictures and the talk of overflow bottles have me realizing something very funny. The PO of my car and me in turn, (because i did'nt know any better) have been using the washer fluid bottle as a coolant overflow bottle.

Now that's funny.
Sorry, but true.

[newman27]

Originally Posted by newman27 ...I have been trying to find a 14 PSI Stant cap and can only find 13 PSI caps locally. The SP-21 part number isn't registering anywhere either. FWIW, The FSM says to use a cap that is rated 13.2 - 15.2 PSI. That said, doesn't the single number rating on the cap translate to a higher SAE range like the FSM is quoting?

Related to this question I posted, take a look at the radiator caps that Rock Auto specifies for the GT in the attached screen shot. The Stant Part #10329 cap is the one I would think to be appropriate. It is a 13 PSI cap but has the SAE range posted in the description. Can someone explain this please? I have been on a few different auto sites trying to find the answer as to how the cap PSI rating is related to these SAE ranges and can't seem to find the answer. My guess is that that is just the range of pressures over which the cap is guaranteed to operate but would like confirmation.

Thanks!

Matt