need help with Telsta a28 hydraulic leak please

[Fred68]

I believe its a 1989 model. Inside the pedestal, behind the valve bank, there is a blue block with 2 hoses on it and what seems to be maybe a solenoid on the top. Its very hard to see with all the hoses in the way but when I start the onan, I can see fluid gushing out where the base of the 'solenoid' meets the block. I thought maybe it was for emergency lower, which is disconnected anyway, so I tried to bypass it. The leak stopped of course, but now the boom won't operate.

I would be very grateful if someone could shed some light on this for me. Like, what is that block for and can it be overhauled to fix the leak or if its not a critical function, how to bypass?

Thanks for any help you can offer.

 

[Fred68]

Since nobody on this site seems to know anything about this, I decided to post more information for the next guy with this problem.

The block is for emergency lower and it is a solenoid. A nut must be removed from the top to take off the electrical part of the solenoid. Under that, is the valve part which is removed with a large deep well socket to reveal several Orings. Replaced those and fixed the leak. Its a simple fix if you can squeeze your arm in there.

Now that this info is out there, maybe the next guy won't miss 3 days of work. Cheers.

 

[willie59]

Sorry to hear about the downtime Fred68, I just now saw this post. I sounds like you're describing a cartridge type solenoid valve, most likely was leaking at that top seal o-ring just under the hex. If that's so, and you replaced that o-ring, keep in mind that it may be an SAE o-ring boss connection and requires a 568-900 series o-ring. If you used a different series, like 568-200 it won't work and will blow that o-ring again. And you should get that emergency lowering working. If you work by yourself, it's likely one day something will go wrong with the unit and leave you stuck in the air, I've see it happen before to guys working alone.

Good to hear you got the problem sorted out. :drinkup

 

[Fred68]

Thanks for the O-ring info. I used one from a kit I had so its probably the wrong kind. I'll get the right one before this one blows out.

My emergency lower was causing electrical problems so I disconnected it. We always have 4-6 trucks on the job so its not really needed.

A new problem has emerged though. Since i couldn't see inside the pedestal very good, I took apart the very similar elevation solenoid on the outside to see what I was dealing with. Now, the up/down function is sticking on in both directions. I can change direction but it won't stop moving unless I turn off onan. When I restart, its fine until I use the up/down.

Any ideas?

 

[willie59]

Well, no way I can be certain it's an SAE o-ring port on that valve without seeing it myself, just letting you know what o-ring it takes if it is. Here's a chart that shows a typical SAE o-ring port, notice the taper at the top of the port to accept the o-ring seal. Also, if you have any JIC plugs for hose fitting plugs, the threads of JIC plugs/caps are the same as SAE o-ring fittings so you can use them to identify the size. Note on the chart that a #8 JIC (tube size -8) has 3/4-16 threads and uses 568-908 o-ring.

http://www.hyvair.com/pdf/saeoringport.pdf

As for the control valve problem, I'd have to know more about that valve to have any thoughts about what's causing that.