Rubber Tensioner

[bmohr]

Kevin,
Since it sounds like you might not have access to an original tensioner and there's been nothing conclusive posted on the thread, I propose you do the following test. Put the new tensioner in a glass jar with 50/50 mix of old and new oil. Since you live in sunny San Diego, let it sit in the sun for a week. It's not going to get to operating temperature, but it will probably hit 100 with direct sun. That plus the longer term exposure and cooling down at night should give you some indication. Just take some measurements ahead of time so you can detect even smaller changes in dimensions. HTH

 

[Q]

Tensioner rubber II

Bill-you are correct, I do not have an original tensioner rubber. I need to get the car back together for the British car show in San Diego October 13, but like your oil soaking idea. I think I will purchase another and leave it in a used oil filled jar in the San Diego sun to help gauge the depreciation rate of the rubber in oil. I am attaching a couple of photos of a new replacement next to the split and swollen "original." It doesn't include all the rubber chunks that were washed out (or may be caught in the oil filter).

 

[mightyohm]

Wow. I am glad I did a search because I didn't realize there were so many problems with the reproduction rubber timing chain tensioners. I ordered a tensioner a couple years ago from Sunbeam Specialties and it is a noticably softer rubber than the original tensioner that was in the car. It's been a few years since the last reply to this thread. Is there a known good source for rubber tensioners today (in 2018)?

 

[mightyohm]

Here's a comparison of the various rubber parts I have on hand.

Top is a new tensioner sold by Rootes Parts in NL. They are saying that this one is oil resistant, but it is significantly larger than the original part and I couldn't get it to fit under the timing cover.

Middle is new tensioner sold by Sunbeam Specialties within the last 2-3 years.

Bottom is a lightly used tensioner (at least 25-30 years old). It's in fairly good shape except for a small crack in the rubber near the pivot end.

You can see that the shape and thickness varies considerably between the three parts.

Is the middle part from SS the one that folks have reported swelling after the first couple hundred miles?

 

[Gary T]

Note that Sunbeam Specialties catalog on page 3 warns that using engine oil supplements to reduce engine wear as well as "High Mileage Oil" will cause the rubber chain tensioner to expand and could result in engine damage. Please be aware of this feature.

 

[mightyohm]

The best solution for me is to re-use the factory rubber tensioner.
(Fact- I haven't seen a factory tensioner that was swollen as bad as the new replacements they sell today. Don't throw them away)
Jan

Jan, thanks for the advice. I'm not a big fan of reusing 30 or 50 year old rubber parts but maybe it is the best option given the lack of good alternatives.

 

[moonstone SIV]

Haha....that RPS tensioner is a joke, like many of their other products. Why do suppliers/manufacturers continue to produce/sell products that are "almost but not quite the same" as the OE items. If it's not correct then don't bother, and stop wasting the time and money of car restorers that want a quality item. GRRRRRRRR.

 

[Ken Ellis]

I agree with moon, but wonder if a few minutes with a stationary belt sander could re-profile appropriately. But the 'feature' claimed by SS (as reported by Gary) would give me pause.

 

[Jimjordan2]

I'll chime in here, as this happened to me also. And nothing I'm saying is against Sunbeam Specialties. I have a lot of respect for Rick and his crew and their knowledge.
But, I installed a new tensioner from SS, and know for a fact that I did not use any oil additives, added nothing but standard 30 weight oil, I was astonished to see how that rubber swelled and was destroyed. Nasty, nasty.
I also agree, that of the 4 engines I've been into, the originals had no swelling at all, and I'm now reusing the old ones.
I also must agree that the suppliers should be going back to the manufactures and demanding a correct product. One hell of a lot of work to replace a product that shouldn't fail.
Just my 4 cents worth. (inflation)

 

[Jimjordan2]

Now, to take it a step further, I also have a couple with small splits, or cracks, what would your opinion be of sealing the rubber to the metal tensioner to try to strengthen the crack in the existing rubber? My splits are not on the pivot end, but the small end. And I'm talking minor split, just a weakness it would appear. I know the one in my existing engine has a small split there and doesn't appear to be a problem (at this time.)
Ken, you may have a better idea with reforming the new one.
But why should we have to?

 

[Ken Ellis]

Jimjordan2 wrote: "Ken, you may have a better idea with reforming the new one."
Maybe not, if it cannot stand up to modern-day additives. I agree with your "But why should we have to?" Especially if 50-year-old ones stand up well in comparison. Anyone big into rubber formulations?

 

[mightyohm]

I contacted Rick and he said that he is no longer selling the rubber tensioners. I'm not sure if this is because he ran out or because there were problems. He is looking into getting new tensioners made from a new material, possibly Viton.

Greenwood in the UK is selling tensioners on eBay. They look slightly different than the ones I have on hand. They said they have never heard of the issue with swelling.

Speedy Spares sells tensioners with the same warning about modern oils, so they may be the same ones that Sunbeam Specialties was selling for a while.

I wonder if anyone has tried retrofitting a hydraulic or spring tensioner from an MGB or other make. The Alpine tensioner is pretty crude by comparison.

 

[moonstone SIV]

SUPPLIER ALERT...

Be wary of stuff from Greenwood in the UK also. I recently ordered rings, bearings, tensioner and timing chain from them via ebay. The rings (TPS? brand) were the only items of correct spec. Their AVP branded timing chain was surface rusty, the bearing shells were poorly finished and covered in tiny "pimples" and I think from memory the tensioner was also dimensionally incorrect.

When questioned I was given the usual brush off of "we've sold hundreds without complaint...." and when I pushed for a refund they became obstructive and it took forever. Like RPS I would not recommend them to anyone. By comparison Speedy Spares are helpful, prompt with communication and supply and if there is a problem it is quickly resolved with little fuss. Once again, buyer beware....

 

[Ken Ellis]

Now, to take it a step further, I also have a couple with small splits, or cracks, what would your opinion be of sealing the rubber to the metal tensioner to try to strengthen the crack in the existing rubber? My splits are not on the pivot end, but the small end. And I'm talking minor split, just a weakness it would appear. I know the one in my existing engine has a small split there and doesn't appear to be a problem (at this time.)
Ken, you may have a better idea with reforming the new one.
But why should we have to?

I'm not sure any 'glue' or adhesive would be worthwhile on an oil-soaked original unit. If pressed, I'd sew it together (or reinforce it) with nylon zip ties (the one place I'd use ties without the metal tab in them) and maybe melt the zip interface with a soldering iron. Mechanically it will be strong enough if you use a couple of them -- as long as the chain isn't directly on the zip ties. Oil resistance should be fine. Sadly, Sunbeam karma will be low, however, because it's somewhat of a kluge. But if the zip ties go walkabout, they shouldn't damage anything mechanical, and they would be too big to get sucked up in the oil passages. Still lame, though. Sad I even wrote it up...

 

[Alpine 1789]

Does anyone know the approximate time window of the bad batch of tensioners? This discussion has brought back something that has nagged at the back of my mind for years. I rebuilt my engine in 2004 (maybe earlier) and am virtually certain I would have installed a new tensioner from SS. While I don't drive the car nearly enough, wouldn't the rubber have deteriorated to nothing by now? I am not sure exactly what symptoms to expect, but everything seems ok. Still...

 

[Jay Laifman]

I rebuilt my engine with a tensioner from SS in '96 or so. I have not taken it apart since. So I don't know if I'd know if I had a problem. But I haven't noticed anything.

 

[Alpine 1789]

Thanks, Jay.

 

[Jaars]

It must be a worldwide problem, and not enough warnings spread around.
My friend Franck in Paris send my the alarm below about the chain tensioner quality problems. I was not aware of this, and hope my engine is ok.
I found this info here. So the only solution is to make sure to use "old fashioned " oils? Like Motul Classic?

" Different magazines or forums warned the Sunbeam owners not to fit new rubber chain tensioners. I CAN CONFIRM THIS ! A new one which has been enlarged about 50% on the lower half, the upper being transformed in black porridge in the sump. Fortunately the bearings didn't suffer, but you know how difficult it is to fit the 2 side paper gaskets, and the 2 rectangular cork gaskets. Please recall this information to any who would be rebuilding his engine. Franck "

My Dutch friends discussed this with Rootesparts.com. Many years ago, he mentioned that the original rubber tensioner is not fit for modern oils. He had remanufactured new tensioners made of a correct rubber, even for use with modern oils. His website has a relevant remark.
In one of the workshop manuals on Rootes.com there is a mention:
ENGINE CAUTION: NEVER USE AN ENGINE OIL SUPPLEMENT OR “HIGH MILEAGE OIL” TO TRY TO REDUCE ENGINE OIL LEAKS. THESE ADDITIVES WORK BY SWELLING THE RUBBER SEALS WHICH THIS ENGINE DOES NOT HAVE. HOWEVER, THE TIMING CHAIN TENSIONER IS RUBBER & IT WILL SWELL AND BE DESTROYED IN THE ENGINE REQUIRING AN ENGINE TEARDOWN. THIS IS VERY IMPORTANT

 

[65beam]

Robert,
High Mileage oil has a seal conditioner in the additive package hence the name "High Mileage". This causes rubber seals to swell which stops leaks. The problem we have with the Sunbeams is the tensioner is rubber and as a result it swells. Todays conventional engine oils do not have the seal conditioner in the additive package so there should be no problems using these oils. There are synthetics that have seal conditioner added.

 

[Andrew]

Tell you what is going on here guys. I have been designing a pump that can be used to pump fuel, diesel, oil etc that needs to pass UL124 certification. 95% of rubber now only passes standard oil and fuel tested with Ethanol. Try to find one that is good with Methanol and you are hard pressed. 95% of Nitrile is only good for Ethanol Blends and even some of these will deform when socked in oils. It has taken me 12 months to find some good products, thank goodness for Parker Hannifin and their products. Who ever is making these parts are not doing the correct deformation testing on their parts and I bet they are not testing them with Ethanol and Methanol (and other oil additives). It would be great to see them step up and use the correct material. Old parts are the best, just like us old guys!