My radiator (stock 87S4) is leaking form the seals at the end cap. The questions are:
1. does a "rebuild" with new seals do the trick?
2. are new end caps necessary/recommended?
3. Shoudl I just get a new radiator? If so, is there a specific one recommended?

I am also wondering if an aluminum unit can be found for far less than what the 928 vendors are selling them for...

Thanks in advance,

Neil

 

Neil, the leak is most likely due to a crack in the edge of the end-tank.

Presumably it looks like its leaking from the seal up where the hot water flows in from the engine to the top of the radiator? That's where the common leak is.

I replaced the whole end-tank - you can buy them as a complete unit, and then unbend the tabs or the frame (there's a thread by Shark Attack somewhere here where he did it without bending (and inevitably breaking) the brittle aluminum tabs holding the end tank on.

 

S4's can be equiped with a brass or aluminium core, what core does your car have?

+1 to Hilton's suggestion, so definately determine where the leak is. You can usually find the leak when the engine is up to temperature, shut it down and listen and look for the leak.

In addition the end covers sometimes develop a leak at the joints and these can be tightenen up by using some multi-grips the bend the tags some more to compress the seals a little. This depends on the condition of the rubber seals ( hardened?).

If you have a leak in the core tube these can be repaired on both brass and aluminium radiator cores.

If you have a brass core then the tube can be soldered or if the leak is at the juncture of the tube and the end plate it can also be soldered. The area must be thoroughly cleaned first.

If you have an aluminium core and the leak is in the tube or where the tube enters the end plate, this can be repaired by using a two part epoxy sealant such as made by Permatex.

Leaks can also be repaired by actually blocking off the holed tube, but his requires both end plate to be removed. Only a percentage of tube can be blocked off.

I just repaired an aluminium cored radiator that had a leak at the joint of the tube and the end plate by using Permatex. I removed abouit 10 or so mm of fins to expose the area. This repair was on a GM car and the pressure in the cooling system is 135 kpa. On pressure testing cold after the repair I had a small weep, detected by soapy water - bubbles.

It was interesting to note that when the coolant is changed GM recommend that you put 3 of their (GM)pallets into the system, to protect the hoses, lubricate the system and to prevent small leaks. I believe that the pallets are ground walnut shells and you crush them up before putting them into the radiator hose before reconnecting and starting the engine. After starting the engine I brought it up to operating temperature, no leaks detected at full operating pressure.

When you have found you leak, you can determine what need to be done, so shop around to get the best deal or if you are a DIYer then what have you got to loose, except that you may save yourself considerable expense.

Let us know what you find and we will go from there.

Tails 1990 928S4 Auto

 

You can replace the end tanks and seals as an inexpensive solution but it will take patience and care to keep the tabs intact - couple hundred bucks max. Or you could replace it with a new factory radiator for a ridiculous amount of money. I chose to go with 928 Motorsports' aluminum unit for about half the cost of the factory one and I really like the result. It's a work of aluminum art and I'll never have to worry about the radiator again, period.

 

buy a new end tank and the new end tank O ring seal take the radiator to a shop that repairs plastic end radiators
tank -95.00
labor 75.00
this is a good idea of the cost.
The reason the passenger side tank cracks is because there is a small air pocket inside the top of the rad and it runs hotter than the rest of the area over time this area gets brittle and then the plastic cracks along the edge near the clamps.
Dont try to re clamp the tabs you need a new tank

 

My mistake - the thread I was thinking of was by Jhowell.

Its here:

https://rennlist.com/forums/928-foru...king-tabs.html


I've done end-tank removal/replacement twice, both times painstakingly bending tabs (and breaking a couple). Next time I'll be trying it per the thread I linked - seems to be much easier.

 

1. If the leak is coming from a crack in the end tank or a bad seal between the end tank and the aluminum core, then yes, a "rebuild" will work.
2. You should get new end tanks. Even if your tanks aren't leaking now and you manage to just replace the seals, what's to stop the 20+ year old plastic end tanks from leaking 6 months down the road and forcing you to do this repair job all over again?
3. Unless the aluminum core is leaking or somehow damaged, I don't see a point in replacing the stock radiator because the end tank leaks.

Xlot posted a link to the write-up I did last summer. After breaking one or two tabs, I figured out the trick to remove the tanks without breaking any tabs. Due to a leaking transmission cooler, I actually wound up having to remove the tank a second time utilizing the same method and broke no tabs the second time around.

 

Thanks, guys! That 928 motorsports rad is a tempting gem, but The rebuild writeup makes it look so easy and cost effective. I don't know if I'm any closer to a decision, but at least I am better informed!

 

You can also use do it this way, I think it is cleaner as the tabs do not like to be re-bent (many will break).
If they do and that core is good and clean, just make up some U channels like this, i have now been through a few HOT summers and no leakes


https://rennlist.com/forums/928-foru...h-no-tabs.html

just another option

 

New Porsche radiator prices are absurd. Why on earth are the prices soo high? I remember buying my BEHR Mercedes radiator for the 500E for about $390.00 a few years ago. I bet the capacity and size were similar and the car had transmission coolers built into the radiator too.

 

Gawd that looks so sexy (never thought I'd be looking at a picture of a radiator on the Internet and saying THAT!)...

Assuming the radiator itself is in good shape (and it should be if there have been no accidents or debris kicking up into it) the rebuild sounds like the way to go...

 

I did an end tank replacement many years ago ... had it put on by a rad shop also. Three years later the replaced end cap split open like a fat man's trousers at the most inopportune time. I don't know if I was unlucky and got a bad part or if the install was faulty ... but I can tell you that I feel a lot more confident in taking a trip in a 22 year old car with the all aluminum welded radiator. Sooner or later the plastic will fail again and I think that, in the long run, the all aluminum rad is a better value and less headaches.

 

Replacing the end tanks, done properly, is definitely a good way to go and the most cost-effective. Personally I just like improving where I can and since I didn't need either internal cooler, the cost was really not that much more than replacing the tanks and seals. FWIW I still have my factory radiator in the garage, complete with a split end tank, cheap to interested parties!

 

We must be lucky down here in Oz - year or two back the inlet tube broke in half on my 83S. The local radiator shop got me a NEW alloy unit, complete with 2 coolers, for A$880, in 2 days. Geniune 2 cooler unit lists here at around A$2200 . No problems so far.
jp 83 Euro S AT 52k