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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars

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Old Nov 25th, 2020, 19:35   #11
Laird Scooby
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Electric vacuum pump for cruise control is mounted on the inner wing/wheel arch in line with the strut tower. Electric headlight adjusters are indeed in the same area to the EVAP canister but are rectangular and mounted directly to the back of the lamp casing whereas the canister sits lower down in the "battery" tray.
Electric vacuum pimp? What's wrong with using manifold vacuum and a vacuum tank like every other manufacturer on the planet?

Granted on a diseasel you don't have that luxury but there is a vacuum pump there for the servo (often mounted on the back of an alternator depending on the vehicle) so would only need a tank and maybe an NRV to prevent the brake servo being deprived of vacuum.

Is it over-engineering or over-complicating?
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Old Dec 3rd, 2020, 00:52   #12
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Is it over-engineering or over-complicating?
We've come to expect the former with Volvo but you could argue it's also the latter Dave with the extra kit that's involved

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Originally Posted by Laird Scooby View Post
What's wrong with using manifold vacuum and a vacuum tank like every other manufacturer on the planet?
All of us with air conditioning on our Volvo's know that there's barely enough manifold vacuum to operate that system, more so if there's any leaks, when the engine is at high speed/high load eg. climbing a hill with wide open throttle. The cruise control system is self sufficient, I guess so that the required vacuum is available continuously for as much as required, regardless of engine speed/load and thus more reliable as an overall system.
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Old Dec 3rd, 2020, 06:28   #13
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We've come to expect the former with Volvo but you could argue it's also the latter Dave with the extra kit that's involved


All of us with air conditioning on our Volvo's know that there's barely enough manifold vacuum to operate that system, more so if there's any leaks, when the engine is at high speed/high load eg. climbing a hill with wide open throttle. The cruise control system is self sufficient, I guess so that the required vacuum is available continuously for as much as required, regardless of engine speed/load and thus more reliable as an overall system.
There's a lot of stuff i've found where Volvo have unnecessarily over-complicated things.

If you're suffering strange things happening with your A/C on WOT then i'd guess you need new NRVs - had a similar problem with mine, traced it to the NRVs and renewed them. One was definitely FUBAR and as the other one was the same age, i renewed both. Only cost a couple of quid on fleabay for some generic ones that fit. You should have a reservoir built into the system, on the 760 it looks like 3 tennis balls in a sock :





There is a seal in it, three screws securing the front and back halves (if memory serves), if it's leaking then pull the seal out, smear it with silicone grease and refit, nine times out of ten that fixes it. The 10th time you need silicone sealant instead or a new seal.
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Old Dec 8th, 2020, 00:54   #14
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After owning it for a year and a half I'm still making "discoveries" on my MkII 960 [an early one was no dipstick for the auto box]
Every single Auto 960 has a dipstick for the ATF. It is tucked down low on the intake side up against the bulkhead. I have just about every year of 960 for first to last and the position is the same on every single one of them. The top is usually yellow
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Old Dec 8th, 2020, 10:14   #15
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I thought I'd had a thorough look for the dipstick and not seen one will have another look see.
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Old Dec 8th, 2020, 22:29   #16
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had another look today and of course you're absolutely correct classicswede! Even following your description of where the g/box dipstick is I still nearly missed seeing it a little more thought by Volvo engineers/designers and I reckon they could have got it even lower in the engine bay and impossible to get to rather than just being bleddy awkward!!
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Old Jan 2nd, 2021, 01:55   #17
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Thanks for your input here Dave.

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Originally Posted by Laird Scooby View Post
If you're suffering strange things happening with your A/C on WOT then i'd guess you need new NRVs - had a similar problem with mine, traced it to the NRVs and renewed them. One was definitely FUBAR and as the other one was the same age, i renewed both. Only cost a couple of quid on fleabay for some generic ones that fit.
When I eventually get round to this job, I intend to go through all the vacuum circuits with a fine tooth comb for leaks. I know from experience that the black rubber connectors perish and crack with age. But like you say, non-return valves are also prime candidates.

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Originally Posted by Laird Scooby View Post
You should have a reservoir built into the system, on the 760 it looks like 3 tennis balls in a sock :

There is a seal in it, three screws securing the front and back halves (if memory serves), if it's leaking then pull the seal out, smear it with silicone grease and refit, nine times out of ten that fixes it. The 10th time you need silicone sealant instead or a new seal.
I've had cars in the past where you can hear a hissing noise from behind the dashboard so the vacuum reservoir will also be looked at regardless.
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