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Third Radiator In 98 Boxster - Hose Size Question


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For those who have added the third radiator to a base Boxster - what have you done about the different hose sizes? I see that some people put copper reducers in, others just tighten the hoses down despite the difference.

What's the preferred/easiest method?

Steve,

The hose to mail pipe connection in my experience is the most common area for failurer hose failure. I've never sseen a hose split anwhere else.

The a larger hose isn't a great idea, it's compressing the hose where it doesn't want to be and stressing it to early failure. Were I to go that that route, I might pick a hose I.D. with an average of the 2 different male rad. pipes I.D.s, Stretch one and compress the other. (silicone rubber can help you lubricate the tight one). spread the strain in half but…in two places now

On the other hand, a reducer will be a lot easier on your hoses and let them reliably live longer. However, you obviously have twice as many connections fail.

Ideally you would be to get your auto-parts emporium smurf to let you mosey down behind the counter of the radiator hose isle and see if you can find something that will work either of the shelf or with some trimming. There are lots (most?) of hoses with 2 different end sizes.

Regards, PK

Edited by pk2
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For those who have added the third radiator to a base Boxster - what have you done about the different hose sizes? I see that some people put copper reducers in, others just tighten the hoses down despite the difference.

What's the preferred/easiest method?

Steve, I'm not sure what size issue you are referring to; I've done a couple of these using kits from Suncoast that came with the correct hoses, and everything fit fine...........

kit.jpg

Edited by JFP in PA
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I just got the kit last night, but from what I've read and haven't tried it, the hoses in a Boxster are a smaller diameter than the hoses in a Boxster S or 996. The hoses in the third radiator kit have 996 part numbers, so supposedly they are are bigger.

If you haven't had an issue, hopefully I won't either.

You don't by chance have the part numbers of the hoses in the ones you have done, do you?

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There is a difference in hose sizing from the Boxster 'S' and the normal non-S cars. You need to "down-convert" your hoses to the smaller diameter size if you are installing the third radiator on a non-S car. I cover this completely in my tech article (http://www.pelicanparts.com/techarticles/Boxster_Tech/31-WATER-Center_Radiator/31-WATER-Center_Radiator.htm) - the other tech articles available on the net don't cover this aspect for us non-S owners.

Hope this helps,

Wayne

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I used the KIT and the hoses in ths KIT are larger than the boxster (non-S) connections. I just clamped it tight. No leaks yet?

Ditto. But thinking about it later what could have been done is slid a smaller hose on the inside. Basically doubling it up.

Maybe it's been a year since i have done it and no leaks yet. Well a leak the first day then i put two hose clamps on

and cranked it up.

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I saw your article, Wayne, but it is unclear which hoses you cut - maybe it will make more sense when I get in there and look.

Hmm, I thought it was clear, I'll have to take another look at it. Here's the photos and captions:

Pic6.jpg

One of the problems with the upgrade kit is that the pipes on the regular Boxster are smaller than those on the Boxster S. The trick is to cut the hoses and create a step-down hose using a copper pipe reducer available at any good hardware store (outside diameter 1.25” x 0.875”). A- The regular hose and the larger Boxster S hose are shown side-by-side. B- Cut both hoses at similar points. C- Insert the reducer into the larger diameter hose. D- Join the two pieces together and secure with hose clamps.

Pic7.jpg

hese two photos show the left and right side of the inner wheel wells with the larger radiator pipes installed (yellow arrows). In addition to the larger diameter pipes, you also need to install the plastic larger diameter pipe retainers (green arrows). One end of the pipe attaches to the new three-way radiator hose (red arrow), and the other end of the pipe attaches to your custom-made hose with the reducer piece installed (blue arrows).

#################

The BLUE arrow points to the radiator hose that you should use the adapter on.

-Wayne

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I used the KIT and the hoses in ths KIT are larger than the boxster (non-S) connections. I just clamped it tight. No leaks yet?

As the hose ages, it will probably begin to leak. There's just a bit too much play in the hoses. Still, if it's installed and not leaking yet, I would probably leave it alone until it does decide to start leaking...

-Wayne

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  • 3 weeks later...

At this point, I could not be any more upset by this project. I have now had the car apart for a week working on getting the new radiator in. My idea was to cut a small piece of old hose and put it inside the new hose to take up the slack - seemed to work great, and I finally after several nights of fighting hose routing and installation, got everything back together. Added coolant, got the car up to operating temperature, and wouldn't you know it - the threads embedded in the smaller hose starting wicking coolant - you could see little beads of coolant where the threads were. So, I tried putting some silicone sealer on it - still leaks. So, I tried to find hose that doesn't have thread in it - turns out NAPA sells a kit just for this kind of thing that just has rubber hose, but the smallest they have goes from 1 1/2" ID down to 1 1/4" ID, and I need to step down from 1 1/4" ID to 1" ID.

I don't particularly want to just tighten the big hose over the line, for the reasons mentioned above, and I'm not real wild about spending another $150 to do Wayne's idea, especially after having spent $500 on the kit. You'd think that for spending $40 a piece for Porsche coolant hoses, they would make one that actually works, but I guess not.

If anyone has any other ideas, I'm all ears. I was trying to get the car back together for the track next weekend, but I'm quite obviously not going to make that.

I cannot believe that it has to be this complicated going from one hose size to another, or that Porsche has not made the correct lines for installing in an older car.

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Something must have changed since I did one of these (which was some time ago), perhaps they stopped making the "stepped" hoses and went with the OEM stock "S" layout units. In any case, I think that Wayne may have your solution, with one exception: rather than just use the single copper plumbing adaptor (which has very limited gripping surface for the hose), I would also sweat a short length of the correct size copper tubing into both sides to give you more surface to grip to. Parts shouldn't cost all that much, and should only take a few min. to cobble togeather..............

copper-fitting-reducing-coupling.jpg

Edited by JFP in PA
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Well, I think I've hit upon the answer.

The trick is that you need a rubber hose 1 3/4" long, 1" ID, roughly 1 1/4" OD (it can be a little bigger, as the outside hose will stretch a little). The other requirement, as I mentioned above, is that the hose must be made of solid rubber, not rubber impregnated with thread, as coolant hose is.

I went to Lowe's today to see if I could find something that would work - I didn't really want to use PVC hose, and none of the other broad selection of hoses looked good. However, I finally hit the dishwasher isle, and lo and behold, a dishwasher to disposal rubber hose seemed to be the answer - the OD is about 1 1/4", and the ID is 7/8". Also, it is made to handle hot water and pressure, so it seemed an ideal choice. Plus, they were $1.79 a piece, so I thought I'd at least try.

I brought them home, and cut each one 1 3/4" long, which cuts off the narrower section. I then test fit on the hard line on the car - unfortunately, the 7/8" ID would not stretch quite enough to slip over the hard line. So, I got out the Dremel with a sanding disk and sanded the inside down until it was about 1" ID, making sure to keep everything as smooth as possible on the inside. I then thoroughly cleaned out all the rubber bits, and test fit on the car - perfect!

I have just now put everything back together and ran the car up to operating temp, and everything looks good - no leaks (though this time, I did use double hose clamps on the hard lines). I'm going to let it sit overnight and check for leaks tomorrow, then run another test up to operating temperature. If all looks good, it will be time to make the template for the front bumper and start cutting, then (FINALLY) get everything back together.

Anyway, thought this might be helpful for those attempting this in the future, and it saves a lot of money over Wayne's solution.

It's the part in the lower right of this picture - you can buy it separately from the hose.

091712985259lg.jpg

Edited by steve_wilwerding
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Steve, the reason that automotive cooling hoses have "threads" in them is the same reason that tires do: Strength. Long term strength under pressure, temperature, exposure to glycols, and vibration/flex are required for automotive hoses to survive long term. The last point is important as automotive hoses have to be able to flex and bend while hot or cold; dishwasher hose does not, and only sees dirty tap water. The parts your photo shows are for a dishwasher drain line, which is very low pressure (a small pump pushes drain water into your sink, venting to atmosphere), so they are not designed to stand much pressure. My concern would be that the dishwasher hose will give out and require pulling the nose apart again after flat bedding the car home. I’d go with automotive hose and some sort of adaptor…….

Edited by JFP in PA
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I agree with you in the sense that you wouldn't want to run lines of that type - however, if you look at the specs for that fitting, it is meant to stand high temperature and pressure up to 200 psi, which is far more than a Boxster runs by a factor of about 15-20. Also, consider that is is really just sleeving the hard line - it is not "free standing", and therefore doesn't need to be very durable.

I suppose you're correct in saying that it could blow out, but I figure it's about as likely as the other folks who tightened the large diameter hose over the small diameter hard line, or the probability of it leaking or blowing out with a smooth copper fitting in the line. I guess I'll take my chances - I rarely drive my car far from home, so if it needs to be flat-bedded at some point, so be it.

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Steve,

If you can find a better solution that works, then fantastic. But I spent a lot of time in Lowes and other places trying to find the best leak-free solution, and the one I decided upon really worked well (no leaks). You can use my adapters on the 3-way hoses - you don't have to use them on the s-hoses, but clearance is tight then. So, take your 3-way hose and lob the end of it off, and then use a regular non-S hose that goes from the side pipe to the radiator and cut a small section of that off as well. Then use the adapter to join them together. Basically, you're modifying your 3-way hose with an adapter on the end. If you're trying to save money, that's the way I would go.

I'm with JFP - the dishwasher stuff doesn't seem like it would stand the test of time or the environment. It's a lot harsher in the front of your car, than it is under your kitchen sink!

-Wayne

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After some consideration, Wayne, I decided on your approach, and ordered the parts from Pelican on Monday. Now the next question - anybody have any tricks on cutting the hole in the front bumper. I like Pedro's approach, but any other suggestions are welcome.

Can't help you there as the ones I did had new (GT3 I think) bumpers installed................

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  • 11 months later...

Hi guys,

Just had this done on my '98 Boxster 3.4L

The issue is with the coolant level.

We continue to monitor the coolant level and just when we think things are fine, the coolant light flashes.

While driving the temps are fine so I'm not worried about over heating, however, the level indicated for coolant is low. We top up, I drive a bit, think things are resolved, then light flashes, haha!!

Is there a difference in size from the 986 "S" expansion tank and the non "S"?

Also - Should one replace the water pump at the same time? I'm thinking of replacing the water pump and upgrade to a low-temp thermostat.

Any thoughts and long term updates from those that have completed this upgrade would be much appreciated.

I have no leaks and have put well over 100km's since the upgrade.

Cheers,

Mike

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To return to the original focus of this thread, namely the apparent sizing difference in the later third radiator kits hoses; a company named Precision Chassis Works came out with a sharp solution in the form of a machined "spud" which is welded into the OEM aluminum hard line, resulting in a permanent and leak proof solution:

8421055_orig.jpg?344

They sell the "spuds" for those with access/ability to weld aluminum, or offer finished lines for a bit more.

Their site.......

Edited by JFP in PA
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