I guess the title pretty much says it all - I'm in the process of replacing my radiator and the original foam is about shot - is there any particular kind of foam I ought to use, and where would I get it? Does it even matter what kind as long as it seals things up? I would think it doesn't matter much as long as it can take the heat and other engine compartment conditions, but I don';t know which foams can handle that stuff.

FWIW its a 91 with V12, and an alum radiator going in. Thanks!

 

This is heresy, but I say Forget the foam. If the car is quite OK cooling-wise, which it will be if the fans are good, there are a couple of important advantages:

Much better airflow into the engine bay so less heat-induced wire and rubber tube cooking
Far less chance of rot round the bodywotk surrounding the radiator as it does not get wet and stay wet - which it will even if closed cell foam is used

I left out the foam on Grant Francis' advice and the car is 100% fine. If you must use foam, use self extinguishing fireproof stuff with closed cell. In the Uk it is class O foam.

Greg

 

I'm inclined to leave it out also, but do have one other concern: will the radiator be held in position securely enough by those four pins and rubber grommets? I don't want so expose the new rad to constant vibration.

As for cooling, I'm confident that, as you said, it should be fine without the foam. The new radiator claims a substantial increase in cooling capacity over stock (presumably new stock, not 20 year old half clogged stock) so those tiny spaces should not put it over the edge.

Thanks for your advice!

 

Yes it will be fine. Grant has had his like this for years and driven all round Australia with it.

Greg

 

I would put new foam around the radiator. By deleting the foam, you are allowing airflow to follow the path of least resistance, which will be around your radiator rather than through the cooling fins. To omit the foam would be inviting trouble to a system which is already considered to be the Achilles Heel of the V12.

 

I'm fairly confident that the cooling system will work acceptably without that foam, the new radiator is an aluminum replacement that should have quite a bit more capacity than the stock unit. According to the previous owner, the car didn't have overheating problems, even though when I pulled the old radiator it was probably about 40-50% clogged with crud caught between it and the AC cooler. I'm changing the radiator because it was leaking, not overheating - which I was aware of before buying the car (just bought it about 6 weeks ago).

That said, I don't have any problem with replacing the foam either, but... I don't really know what kind to use, and the stuff that was in there is too degraded to reuse. If it's not too expensive or hard to get I would probably put it back in, but if it's really costly or will be hard or time consuming to source I'm more likely to try without it. I also wouldn't want to have to pull the radiator again to put it in if lacking the foam caused problems.

One other question occurs to me - would leaving that foam out make the car less prone to accumulating crap between the radiator and AC unit, by giving the debris an exit route? From what I've read that seems to be an almost universal problem, probably worse than just having a little peripheral air space around the radiator.

 

As Greg said, I dont run foam on any of my V12's. Tooooo hard for me at the time, and YES, my car my choice.

The daily driver has had NO foam since 1997, and has NEVER run hot. The S2, well there simply is not enough room for foam as it has the "large" PreHE radiator, and no issues either.

There are pages and pages of plus/minus on this, and I am NOT going into it here.

Mine all have twin thermo fans, so "ram air" is what keeps it cool most of the time. My fans rarely come on in any traffic situations.

My opinion again. I dont believe these cooling systems are "on the edge". I believe they BECOME that way by lack of proper maintenence. I got the flame suit on, but for me the proof is in the driving of the car in our wonderful outback in sometimes 50+c temps, works for me.

 

Thanks to all of you for your advice! I'm going to put in the new radiator, hopefully today, without the foam - as long as it seems securely held in place without it.

 

Mmmmmm, maybe I missed something, old age does that.

The foam has NOTHING to do with the mounting of the radiator. It was only to stop air by-passing the radiator. NO newer car has that foam, so I have no idea what the "Guru's" were thinking at that time in motoring greatness.


The radiator as designed is NOT clamped super tight, it has some movement to allow for body flex, hence the rubber on each of the 4 pins.

An alloy radiator will need a little more "movement" I reckon, but dont quote me. Simply look at any modern car with an alloy radiator, and it is quite loose in its cradle.

My XJ-S radiator had significant "float" by my design, and I never had it crack a seam, or anything else for that matter. Prior to my alteration the radiator would crack the solder at the header plate. It was/is a copper/brass radiator, NOT an alloy unit.

My X300 has the alloy/plastic radiator and it has quite a deal of movement on its mounting rubbers. As does "her" S Type.

 

Hi Grant, thanks again for your advice. I don't think you missed anything, it's more just me speculating on how the system works. I had no prior experience with either an aluminum radiator or this pin/grommet mounting system. I didn't really know how snugly the radiator would be held by those grommets, but didn't want it to be shaking around freely on those pins. I did gather from reading that the foam was there to seal things up, but thought it might also function to secure the radiator. Now that it's partly installed I can see that the mounting will be fine without the foam.

It makes sense that the radiator not be distorted when the body flexes, but in my prior experience I think all the radiators I've worked on were solidly bolted in - no vehicles at all similar to this one though, mostly trucks.

I also have heard that aluminum is prone to cracking due to metal fatigue, though I'd heard it mostly in the context of damaged bicycle frames so it may not apply here. Now that it's in it doesn't seem vibration will be a problem anyhow, but that was the basis of my concern.

 

SWEET.

I will have a nice snort of JD to celebrate.

ENJOY.

 

While your at removing the foam, consider installing some flexible tubing from your air filter housing, through the opening you created by removing the foam. The left side is easy, but the right requires a little finagling but can be done if you squish the tubing. I used an old flexible radiator hose cut to length. the right may be squished but will still pass the same volume of air. The hose will also provide a little cushion as the foam once did. Bud