A/C Issues - HELP!

[Dave]

Yeah, find someone that knows what they're doing.

That valve is a high pressure release valve and shouldnt be bypassed. If it has released, or is leaking, you would see it very clearly. Its plain from the picture that it isnt, and hasnt been, the cause of your issues. Did you check the clutch gap?

 

[Chris]

Most AC testers actually put the system under negative pressure. ie the vacuum it out and hold about 1000 something-or-others. Millipascals? Who cares. But you can also have it pressurised with nitrogen as I have in the past. Didn't have any trouble hearing the leak then! Problem with vacuum is that it sucks the parts together. They hold it for like 15 mins. Then stick the gas in. I had that on the grey truck and I got the edge of the car park before I could see a green jet spraying out of the bonnet. I think that on these older trucks you are better maybe, breaking every joint, putting in new o rings and do a good job of sealing them back up then get them filled. At £50 for a complete refill it's an expensive way of working yourself around all the leaks. I'm fuming that my system was bone freezing all the way around Morocco then the gas got out through a loose bolt.

The other one had a pin hole in the pipe near the bulk head. I reckon that with the refrigerant that I have released I must single handedly be responsible for the death of the last blue whale, the dodo and fidgery-poo. What, you didn't know that was extinct?

 

[frank rabbets]

Well it might be a safety valve for overheating of the pump to reduce pressure and cut the pump out but it has not been leaking as there are not telltale oil stains. You cannot bypass it.

If you have had a regass recently and it's now low you have a leak. You most likely have dye in the system so buy a cheap UV torch off ebay and search for the leak. The leak will be luminescent green. Follow the pipes round all the way. There is one which corrodes where it touches the bulkhead. Stand at the front of the car and look where the bonnet closes at the bulkhead. there is a horizontal large bore pipe. They can leak on the LHS looking. The leak is to the back of the pipe and difficult to see.

 

[Chris]

That's the begger Frank.

 

[Dave2000]

To turn up and say it has low pressure followed by there is no leak he is talking out of his hat.

I have replaced the pipe Frank and Chris mentioned. The main issue with that one is it eventually runs near the heat of the exhaust manifold and is kept nice and dry so a leak search is a little difficult. Find an AC guy who knows his onions and go from there.

regards

Dave

 

[clivehorridge]

To turn up and say it has low pressure followed by there is no leak he is talking out of his hat.

I have replaced the pipe Frank and Chris mentioned. The main issue with that one is it eventually runs near the heat of the exhaust manifold and is kept nice and dry so a leak search is a little difficult. Find an AC guy who knows his onions and go from there.

regards

Dave

Bugger, that's why mine isn't working, low on onions! I must have a leek

 

[frank rabbets]

I had to rebuild my pump recently. I had, not related, previously fitted a cheap evaporator. On checking for leaks I found my 2 year old cheap evaporator had 2 leaks on 2 fins. I suspect it had been leaking from day 1. If the Toyota evaporators are as good as the original ones they should last minimum of 10 years. Mine lasted 15.

 

[Dave2000]

Bugger, that's why mine isn't working, low on onions! I must have a leek

Oh dear, not a lot of work about eh Clive?


regards

Dave

 

[StarCruiser]

As all above, to not connect gauges and say the safety blow off valve needs to be removed or bypassed is incredible. Yours has not been leaking as it would be smothered in oily residue. At the very least, he's not done his job properly, at worst, if he's taken money from you, it's under false pretences.

Simple check, get a torch and check for bubbles in the sight glass above the NS battery. Bubbles means it's low, no bubbles means it's empty or full.

 

[frank rabbets]

You and Dave taught me well SC. LOL.

 

[StarCruiser]

You and Dave taught me well SC. LOL.

You were spot on in your post Frank, except it won't shut off the compressor. The valve is an 'if all else fails' safety device that prevents explosion and is something that's fitted to refrigeration systems over a certain (quite small) size. They only vent what they need to. Some smaller systems have fusible plugs which would dump the whole system contents. Not ideal, hence Toyota's valve is the better option, no surprises there Mr T.

I'm now going to go and check my bulkhead pipe as I've learned something from you.

 

[frank rabbets]

Take a painkiller first SC.

That "valve"............I was searching for a word...........and would have used "fusible plug" had it come to mind as I'm sure I have a pump with such a plug. I assume a fusible plug would in fact melt and the compressor would not be able to cut in?

 

[StarCruiser]

Take a painkiller first SC.

That "valve"............I was searching for a word...........and would have used "fusible plug" had it come to mind as I'm sure I have a pump with such a plug. I assume a fusible plug would in fact melt and the compressor would not be able to cut in?

That's right Frank. It would dump all its gas and probably most of the oil too and the system would shut down on the low pressure switch. They make a racket when they go. Either of them, the difference is the valve would shut again given the right conditions.

 

[StarCruiser]

Is this the pipe at the bulkhead? Mine seems to have sound deadening behind it which I would expect to cushion it from wear if not prevent it corroding. Was yours the same?

 

[frank rabbets]

Yes that's the pipe that commonly corrodes. My original one looked like that but slightly different shape and touched the insulation on the LHS looking from where you are. The replacement pipe was a different shape and was well away from the insulation so they had modified it. The trouble with touching the insulation is that the pipe gets wet and water soaks into the insulation and keeps the pipe wet.

 

[StarCruiser]

Yes that's the pipe that commonly corrodes. My original one looked like that but slightly different shape and touched the insulation on the LHS looking from where you are. The replacement pipe was a different shape and was well away from the insulation so they had modified it. The trouble with touching the insulation is that the pipe gets wet and water soaks into the insulation and keeps the pipe wet.

Gotcha. I wonder if I can bend it away? That road may of course lead to disaster.

 

[frank rabbets]

If all the brackets were loosened I would have thought just a pull on the LHS looking would be OK. There would be a pivot point at the connection with the evaporator by which time movement in the metal would be minimal. Then the pipe could be permanently kept away by packing the brackets. If the pipe needs bending just to check for a leeks with mine the dye had soaked into the insulation so was easy to see.

 

[StarCruiser]

If all the brackets were loosened I would have thought just a pull on the LHS looking would be OK. There would be a pivot point at the connection with the evaporator by which time movement in the metal would be minimal. Then the pipe could be permanently kept away by packing the brackets. If the pipe needs bending just to check for a leeks with mine the dye had soaked into the insulation so was easy to see.

I've just had the system de gassed and removed my seized compressor. Had a look at said pipe and decided on doing exactly what you have said, with the addition of wrapping with electrical tape where the brackets go as that's a catch point for salt and damp too according to my mate the fridge engineer whose seen loads on other cars go like that.

 

[Dave2000]

It's interesting that the engineer (and I use the term with care), talked about bypassing the dump valve, perhaps he does not know that if there is a serious leak in the cabin due to overpressure, that the Freon would displace the air and could kill you?

regards

Dave

 

[StarCruiser]

It's interesting that the engineer (and I use the term with care), talked about bypassing the dump valve, perhaps he does not know that if there is a serious leak in the cabin due to overpressure, that the Freon would displace the air and could kill you?

regards

Dave

I have experienced this with a massive fridge leak, and it creeps up on you without you knowing it as the gas is heavier than air. However the cabin side of things is on the low pressure side and the valve is on the high side so that it lets go before any joints or pipes go. It would not normally protect against a cabin leak. The good news is that there is so little gas in a vehicle system and the fan needs to run for the AC to run, that I would imagine the risk from gas in the cabin was negligible (thankfully). The risk on the high side of a frayed hose bursting if the condenser got blocked (with mud, say) is far greater, hence the blow off valve.