The Nissens radiators for the 940 (non-turbo) have a hole in the upper right corner for a sensor to run the electric fan. The hole is unthreaded and has only a short and relatively thin inner neck. In the later 940's with Bosch FI, there is no sensor and the original Volvo rads do not have a hole there (although you can see the mold marks where they would be). Nissens only has the one generic replacement rad for all base 940's. It also has plastic side tanks that have the fittings and holes (all-metal rads are no longer being produced).

There is apparently a friction fit bushing and plug available from Nissens as extra orderable items to fill this hole. You'd think they'd include these small items with the rad, but they don't. I don't know exactly what the bushing looks like, but apparently it's a very tight fit and can be rather difficult to install. Unfortunately for me, apparently there are none currently in stock in the Canadian supply chain. Even if I could find ones in the U.S. they would take up to a week or more to get here and the on-line prices get ridiculuous when you add shipping and brokerage fees. I want to get this car back on the road ASAP.

Anybody run into this and come up with a good solution?

One thought I saw was to use an expandable rubber stopper from a marine supply house -the kind where you tighten a center brass bolt to expand it, but I haven't seen one of the appropriate size.

Another thought I saw was to get a sensor and bushing out of a wrecked 740 or 940, but I'm not sure if the bushings are removable or re-usable.

The hole is too thin to thread even if I could find some kind of plastic or metal threaded plug at a plumbing supplier.

If I could find a snug fitting plastic plug I thought of using ABS cement to glue it in place. I'll be checking out local supply houses later today.

Of course, whatever plug I put in mustn't be able to blow out, especially if the rad pressure rose above normal due to a bad pressure cap or blocked hose. The results could be catastophic for the engine not to mention my blood pressure. There's also the issue of voiding the warranty with a DIY solution.

Thanks in advance.
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Dave -940's, prev 740/240/140/120 You'd think I'd have learned by now

Get a sensor and bushing out of a wrecked 740 or 940, add some black high heat silicon to improve the thread seal, that's the best idea.

Dear David,

Good p.m. and may this find You Well. I have a couple of spare Nissens rads. They came with the bushing and plug, in a plastic sleeve.

The opening in the radiator is about 3/4" (19mm) in diameter. I'd have thought there is a marine type drain plug, of that diameter.

If not, you might be able to do the following:
(a) go to a supply house serving chemistry labs and see if they have a black rubber stopper of the correct diameter, with a single hole in it
(b) get a stainless steel machine screw, slightly larger in diameter than the hole in the stopper
(c) put a washer at the end of the machine screw, where it protrudes from the interior end of the stopper; then put a toothed lock washer onto the end of the machine screw
(d) put a stainless hex nut at the end of the screw, and tighten to the point, that the stopper starts to bulge
(e) drill a hole through the end of the screw, and put stainless wire through the hole and wrap wire around the screw's end (keeps the nut and washer from working loose, falling-off, and getting loose in the cooling system)
(f) put the stopper into the radiator opening, and tighten the screw, until you can't tighten it any more. You might need to hold the stopper with a pliers, as you tighten the machine screw.

I'd get several of the stoppers, so you can experiment with cutting them down. The goal is use a stopper of a length, such that when the machine screw is tightened, it bulges the rubber just on the inside of the radiator casing. That will promote a tight fit.

Hope this helps.

Yours, faithfully,

Spook

And may this find you well too, Jay.

Funny coincidence, I've worked with labs and just happen to have acquired a collection of said rubber stoppers. Of course I originally thought of just stuffing one of those stoppers in by itself, but naturally it could just end up blowing out at some point. Even though I thought about expansion plugs, I simply didn't put those two thoughts together as you did. Your detailed solution is, as always, an ingenious one. Thanks.

In the meantime, it looks like I've been able to source a plug for the job from an auto supplier. The required size is 2 cm (just over 3/4"). These expansion plugs are barrel shaped (as needed) rather than tapered (as a stopper would be). The price is also right at just a few dollars and I certainly don't mind waiting a day for one to be ordered in. For future reference to those reading this thread, it's a Papco 3/4" expansion plug p/n 263548.

As a note to Carlos. I went to a yard today to see about using on old one. Unfortunately there are no pick-n-pulls around so I'd have to pay the going rate for a used sensor (like $35) plus I'd need a new rubber bushing (close to $10 from Volvo) as an old used one shouldn't be trusted and they're difficult to remove without damaging them. The only other thought I had at that stage was using a new rubber bushing and stuffing an old spark plug in it to expand it. That ought to send the next owner's mechanic into a quandry, especially if I run an ignition wire from it to some invisible location, but I digress.

If anyone connected with Nissens ever reads this, why the devil don't you just include a new rubber bushing (almost always needed) and a plug (needed for all 940's with Bosch FI) as standard items with all these rads, rather than separately orderable items? Shouldn't cost more than a whole $3 to do that in quantity and it would certainly simplify all the catalogues out there that lump all 1992-1995 940 non-turbo Nissen rads together without properly listing and clarifying the need for these bushings and plugs. It's bad enough many of them still describe a heavy duty all-metal rad when in fact those are no longer available and only come with plastic side tanks. Whether the plastic sided Nissens are significantly better or worse than the original Volvo plastic sided tanks seems open to debate -search for previous comments here on this topic.
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Dave -940's, prev 740/240/140/120 You'd think I'd have learned by now

Dear Dave,

May this find You well. If you want to contact Nissens A/S, here's an address: marketing@nissens.com . I had occasion to write to them. They responded promptly and helpfully.

I knew that a lab stopper is tapered. I figured that over the 3/8" needed to seal the opening, the rubber would would expand enough to offset the taper. If so, internal pressure would ensure a tight seal.

I'm glad, though, that you've found a straight-sided plug. You might submit the info. for inclusion in the FAQs.

Yours faithfully,

Jay E.

Looks like Nissens beat me to it. Nissens radiators now come with the requisite rubber adapter and plastic plug in a parts bag inconspicuously buried under the rad behind a cinched piece of cardboard. There's no hint of their existence on the packaging that these are included. There's certainly no hint in any on-line catalogues or pictures that these are now included (except perhaps the official Nissens catalogue which I don't have access to). Many catalogues mention a need for the plug and some even give part numbers, but my local supplier couldn't find any in stock -now I know why.

In any case, I apologize for casting aspersions on Nissens. They're certainly one of the most popular aftermarket brands. Just hope their rads last as long as the Volvo ones (apparently made by Blackstone which are difficult to source in the aftermarket). The Nissens installed some years ago by the P/O in my 940 turbo is still looking good. There is no sensor hole in the later Nissens turbo rads.

I must say that the Nissens fitment was perfect, right down to the trim attachment screw holes. There's also a drain plug on the bottom just below the main outlet hose. In the good old days you sometimes had to disconnect the lower hose to drain the rad.

As for installing the plugs in the rad sensor hole, I'll offer a few notes here in case this helps someone (this may later be found in the FAQ). The plug is simply a friction fit, but a tight one and would not likely be the first thing to blow if the rad pressure went abnormally high for some obscure reason. The rubber adapter/grommet/sleeve pushes easily into the sensor hole. Then you push the plug into the rubber adapter. The plug has a rough surface to hold it in place. It's virtually impossible to push it in by hand, although with a suitable tool and enough force you may be able to twist it into place. I've heard of someone using a hammer to set it in, but I don't think that's a great idea as it's hard to get the plug started straight and you risk damaging the rad in any case. The proper way to install it would be with a press. For me, it was quite easy just using a largish C-clamp with a block of wood on the back side of the plastic tank for protection. Upside down in a bench vise or even in a workmate would also work fine. Very large pliers would work, but you'd have to be careful to protect the tank. Install everything dry -there should be no need for RTV or any other sealant with a new installation. If you really are worried about the plug popping out then I heard one suggestion to use a zip-tie around the tank -the plug has a wide slot in the face that would be perfect for holding a tie in place.
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Dave -940's, prev 740/240/140/120 You'd think I'd have learned by now