Write-Up: Replacing Accessory Belt Tensioner

Anyone happen to know the 2 sizes of O rings on these elbows? The 3 reds and single black.

I will be taking mine out soon and I want to have O rings on hand just in case.

Thank you!

charlieRobinson wrote:

Anyone happen to know the 2 sizes of O rings on these elbows? The 3 reds and single black.

I will be taking mine out soon and I want to have O rings on hand just in case.

Thank you!

I can give you the AC Delco part number for the O rings that fit onto the quick connect fittings for the heater hoses, ACD 24502375. I used the metal HELP elbow and it came with a silicone O ring that I slipped into the LIM.

My alternator was squeaking too so I replaced that at the same time as the tensioner. Silence!

Old thread, I know, but others may benefit. Total time spent on the project 2 1/2 hours from seat out to back seat replaced.

Did we ever find out what this gauge means?  I couldn't find anything about it in the FSM.  The FSM does have instructions for testing belt tension, which requires a special tool, so I'm thinking this gauge does NOT indicate whether the tensioner is holding the correct tension or not.  The FSM says something about it indicating whether the length of the belt is within a usable range. Maybe that's the answer but it'd be nice to now what the notches are meant to indicate. It would seem like you'd only need two to define the range of acceptable sizes.

I'm in the process of replacing my acc tensioner and have had a few issues.  Like a couple others I broke the lower coolant passage when removing the old tensioner.  I got the stuck piece out of the coolant passage by prying it out with a screwdriver, but even though I was telling myself to be careful not to gouge the passage I did it anyway -



On reassembly I put a little clear RTV over the gouges.  Now that it's all on, I've re-read this thread and a few others and figured out that I was supposed to lubricate the o-rings before installing.  Oops, didn't do that!  I also found a comment about the incluced o-rings on the aluminum coolant elbow melting.  So I'm going to pull the tensioner, replace all the o-rings, and reinstall with lube.  Probably new antifreeze, or grease.  Unless it's not necessary, although it has to be at least with the heater hose quick connect o-rings.

I spotted this little sensor while pulling everything off the front of the engine -



Who is this fella?

This is how I held the water pump pulley in place while I loosened up the bolts -



No puller needed, so cool!

Does this bolt look familiar? I swear I don't remember pulling anything with a phillips head. Maybe it's from the alternator.

Did you use enough clear silicone RTV to "lubricate" 360* of the port. If so, consider your O-Rings lubricated.

If your going to pull it all apart again, how do you plan to lubricate the o-rings while using some RTV on the small grooves you created. You can't do both at the same time.

How deep are these "grooves".
Your pic's are good and I can see 2 grooves but I don't know how deep they are and if there of any concern.
My biggest concern about the grooves would be if there is any raised metal/aluminum on the edges of the grooves. If so those raised edges need to be removed to provide a nice smooth and round surface for the O-Rings to slide in and seal on.
With a very small amount of raised aluminum in the hole I would use a deburring tool carefully, but most people don't have that type of tool so I would use some fine sandpaper to just get the raised edges off those grooves and provide a nice clean surface for the new O-Rings.  After carefully sanding the holes and if you can still drag a fingernail and feel the depth of the groove after using some fine paper then use RTV for your sealant and lube on that hole.
As long as the O-Rings can seal inside that port you'll be OK.

For holes that are not damaged and you want to lube your o-rings you can use Di-Electric compound, used to keep your electrical connectors free of moisture. It will swell the O-Ring a tad and lube them for installation.

Don't have any Di-Electric, that's OK. Go to your bedside and get that jar of Vaseline. Lube them with Vaseline and you'll be good to go. Seriously Vaseline is used all the time for lubing o-rings. I keep a jar in the garage just for that purpose.

The smaller groove isn't very deep, but the larger one has enough of a lip on it to catch a fingernail.  I hit it with some fine sandpaper but I haven't got it all yet.  I've got a dremel and some grinding stones.  I'm a little concerned about overdoing it with a power tool, but maybe I can be careful enough.  I wasn't careful enough when I pried that broke pipe out though I'm really kicking myself over that one.

JR,
I wouldn't try and use the dremel unless the part was in my hand and well lit so I could see exactly how much material I was removing. That material is so soft, as you now know, that I would just continue with the fine sandpaper. You'll have much better control.
After the rough edge is smooth down then clean the hole real well before installing the O-Ring, etc.

I know I'm not telling you anything you don't already know, but I can't help myself. Good luck with it and keep us posted.

Well I probably would have tried the dremel . . .

Does anyone know how to remove the tensioner without breaking the stupid lower coolant stub? What a shitty design

TampaRivGuy wrote:

Does anyone know how to remove the tensioner without breaking the stupid lower coolant stub? What a shitty design

No, however, once the tensioner is unbolted from the block you should pull out such that you remove the elbow and tensioner as a unit from the block. The plastic elbows are known to crack apart, be sure to fish out and account for all the pieces.

That said, replacement tensioners often but not always come with a replacement plastic or aluminum elbow. You may want to replace the red gasket on the Dorman HELP elbow with a factory one, they are a little different I am told. Consider cleaning the ports on the block (actually the manifold) with a little steel wool and lubing the o-rings on the elbow with a little tune up grease (dimethylpolysiloxane) just before installing the elbow/tensioner assembly.

Albertj

TampaRivGuy wrote:

Does anyone know how to remove the tensioner without breaking the stupid lower coolant stub? What a shitty design

If I'd known it was there I probably wouldn't have broken it. It's my fault for not inspecting the new part better.

That said, the whole idea of flowing coolant through the tensioner is ridiculous and whoever came up with it or approved it has something to be deeply ashamed of. I can't believe that actually got out of the design stage.

BTW, I put my tensioner back on last night with new AC Delco o-rings. How important is the orange coating? I managed to wipe quite a bit off one of them before realizing it was a coating and could be wiped off.

Jack the R wrote:

TampaRivGuy wrote:

Does anyone know how to remove the tensioner without breaking the stupid lower coolant stub? What a shitty design

If I'd known it was there I probably wouldn't have broken it.  It's my fault for not inspecting the new part better.

That said, the whole idea of flowing coolant through the tensioner is ridiculous and whoever came up with it or approved it has something to be deeply ashamed of.   I can't believe that actually got out of the design stage.  

My guess is that whoever came up with running coolant through the tensioner base did not want rubber hoses located near rapidly rotating engine parts (pullies and belts), and for the 3800 mounted transversely it was the most elegant solution (elegant = desired effect achieved with the least effort) that emerged from analysis, synthesis and evaluation.  Keep in mind that "desired effect" is in the eyes of the one paying for the design, and not necessarily anyone who's operating or maintaining things.

I note with interest that belts are lasting *so* long nowadays that Gates recommends replacing the tensioners, pullies and belts as a set. Really. It's getting harder to remember the times when fan and serpentine belts broke more frequently.

Ok, I got Delco O-rings and the dorman aluminum elbow.

What else do I need to be mindful of?

Andrew

TampaRivGuy wrote:

Ok, I got Delco O-rings and the dorman aluminum elbow.

What else do I need to be mindful of?

Andrew

Consider draining a bit of coolant from the radiator before you pull the tensioner. I forget how much, maybe a litre or so?!?

You may want to use a bit of brake cleaner to clean the coolant connections once apart.  Just wipe them first, don't bother with the solvent if they come clean. Your tensioner should have come with new seals for those hoses -- if not, don't wig out they are common o-rings, I think ACDELCO 1534066 ( that would be GM#25537068), GM used them one place or another through 2009, 0.674" or so in diameter.  If you buy parts there often enough the GM counter person may well just give them to you...  

When you R/R the alternator, clean the landings where it bolts on because those are the grounds.  It'll work

PS: did you get a service manual set yet?  If so, I think it's in there (how much to drain).

Then there is this:

https://www.youtube.com/watch?v=lvO_kx_YyQ8

In this video, our hero breaks the end of the elbow by horsing the tensioner off, then has to go back in with a pick tool and fish out the broken bit.  Instead of horsing the tensioner off as he did, once you loosen it consider using a large screwdriver or pry bar to coax the elbow out as you pull the tensioner straight back off the block.  That said, don't feel bad if the elbow breaks anyway. Heat and chemicals make the plastic brittle, although I have only heard of these elbows leaking in place not breaking in place (until disturbed).

Happy motoring, as Esso used to say (after you're done with all this wrenching ha ha).

RTV on the heater core plugs?

Is it easy to loop the heater core lines while doing this (I live in Tampa, everyone heater deletes)

If u buy delco 38152 tensioner it now comes with o rings and aluminium elbow

TampaRivGuy wrote:

RTV on the heater core plugs?

Is it easy to loop the heater core lines while doing this (I live in Tampa, everyone heater deletes)

I didn't RTV on any of my o-rings - but I haven't finished putting the rest of the motor back together yet since I needed a new SC idler pulley. Should find out tomorrow if o-rings alone are good enough. I'm betting they are.

I don't know about looping the heater lines. Off the top of my head, I wonder if the lines on the tensioner would get too close to the alternator pulley/fan.

TampaRivGuy wrote:

RTV on the heater core plugs?

Is it easy to loop the heater core lines while doing this (I live in Tampa, everyone heater deletes)

You could loop the heater core lines but you might not want to. The airbox does a pretty good job of isolating the heater with the damper doors, and there are some conditions in which some air is bled past both the heating and cooling in order to control cabin humidity. You will have to see the service manual for an explanation, however.

The rest of this is for people coming back to read this thread later:

Of course O-rings without a smear of tune up grease will install and work. This is in part because better o-rings, as appropriate for their intended applications have a lube (typically teflon) mixed in to the elastomer, for instance mixed into neoprene before vulcanization. However, generally you use a wipe-on lube on o-ring installation to get around other problems. For instance in some installations, "stiction" can cause the rings, even rings that incorporate teflon, to bind and tear on install, meaning your connection will be leaky and you'll have to do it over again anyway. On the other hand if you lube the ring it's pretty much guaranteed to seat properly.

I found this to be pretty important, for instance, on overhauling the air suspension on my son's Lincoln Continental. I was having trouble getting the connections to behave - the manual didn't say it but a tech at the dealer (Ferarrio) mentioned to be sure to smear a little tune up grease on the rings (I had gone to dealer to get rings when I worked on one of the solenoids). I asked why - he says 'they will seal better' and I did not tell him I'd been having trouble getting the things to behave. Use a little lube -- problem solved.

In some installations, the lube (tune up grease/dimethylpolysiloxane) provides a barrier layer between the o-ring and gases, liquids or metals that would interact with the ring over time. So no sh*t a bit of lube can slow down deterioration/extend the life of of the o-ring. The red stuff on the Delco o-rings is probably a lubricating coating. I don't know what it is but likely it's parylene or teflon. Either one reduces the force needed for assembly and improves the seal.

I have not heard of putting RTV on the o rings but I imagine it's a solution for when the surfaces being sealed are galled badly and can't easily be resurfaced without causing other problems.

I was changing the oil in my Riv the other day, and noticed a drip. It was leaking onto the LIM right where that original elbow goes in. Was very minor. I looked at it after driving the car to work with the engine running. It was dry. I'm sure I will need to do this job eventually, and it looks pretty easy. I have everything I need already on hand.

Are the heater hose O rings different from the tensioner and elbow O rings? Are these the right ones for each?

https://www.rockauto.com/en/moreinfo.php?pk=1309871&cc=1303322&pt=15190&jsn=420&_nck=ZExt1ysfqhqWnq%2BEvUNdS3Txyey60IDtnjPWF5UU9J0BWQv7pvqZbh%2BYrdIIoJ2QVm1wiaiI%2B%2Bo3vjMjN%2Fscq3njoEn03pcGL3JVL3SQ9pzj6wlFfcbFIvUZTrQbIOhSZok5lgJ3iTSiFLXxQB5xQXjSzTiVCMRZoTGy9dVIlBbjMhudGL%2FphoEg%2FQyppT6yKe7pLgXRf0a4Wg1JMXWhXdvGts0pxa6AAzpP2Ltizk9ol54AZM63XdPwp9481thcmPH%2FUqyBD9SHzKx0UcczOOnYxzA5c5kCWdUY0E6xLk0JsAIYHeyjLSrbqrNIyhSBXtNnnVAfbWlG4pBjJ34OmNNevol%2BVw8S

https://www.rockauto.com/en/moreinfo.php?pk=3885342&jsn=276

I think so but I haven't any on hand to measure.

albertj wrote:

I think so but I haven't any on hand to measure.

Well, I will. I have ordered a set of both O rings. I'll compare them when I get them. I want to have everything I need before doing this job. It has never been apart, I am still using the original tensioner. The plastic elbow leaks overnight, but seems to seal up when warmed up. I have the HELP aluminum elbows.

OK, I am a little confused here. The GM 24502846 O rings I have are larger than the GM 1534066 O rings. Looking at the tensioner, the heater hose connections are quite a bit larger than the elbow connection. The specs for the 24502846 say they have an ID of 20.32 mm.

https://www.rockauto.com/en/moreinfo.php?pk=3885342&jsn=276

The GM 1534066 are more than 3 mm SMALLER at 17.02 mm.

Seems to me that the 24502846 O rings are the ones for the heater hose connections, not the 1534066 O rings. Those may be the ones for the elbow?

I have not taken anything apart, so I can't confirm. I just want the right parts on hand when I do the job. The bigger (24502846) O rings seem a bit small in the heater hose openings (new tensioner I have), but I would thing they expand when you put them on the heater hose nipples.