2000 V70R - AWD Rear Sub-frame corrosion

Post by **scot850** » 26 Nov 2014, 17:20

Has anyone else had this happen, and know what the cause is? I've attached some photos that hopefully show corrosion and a crack forming on my 2000 V70R rear sub-frame just in-front of the rear mounting bolt on the LH side. I have the same problem with my 98 V70XC but on the RH side at exactly the same place.

I was just about to put the car up for sale until I pulled the wheel on the last axle to adjust the e-brakes and there it was right in-front of my face. The frame is N/A so will have to try to find a used one hopefully from a dry area without corrosion. This looks like galvanic corrosion between the frame and the sub-frame.

I really didn't need this, but if I have to go in and do this, what else should I look at 'while I am in there?

: LH rear sub-frame rear mount corrosion

: LH rear sub-frame from underneath rear mount

: 2nd photo from underneath showing corrosion

Thanks for help in advance.

Neil.

Post by **scot850** » 27 Nov 2014, 14:08

So I am going to have to pull the sub-frame and replace it. I have never done this before, and need some advice from anyone who has dropped the frame.

Does the fuel tank have to be dropped? I don't need to access the tank for any reason, and it is full of premium fuel, so I don't really want to drain it down if there is no need (I have no where to store it).
Most of the info I have read about dropping the rear sub-frame is to do with accessing the fuel pump, but currently I don't have any issue with that or evap. issues.

If the tank does need to get dropped, then I may take a chance and run the car until the tank is nearly empty before commencing the strip down.

Interestingly, I spoke to the auto wreckers I often use on Vancouver Island (great guys) and Happy (the main part guy) said he has not seen this level of corrosion out there. It is wet out there, but they don't often use salt. Has anyone else seen this issue (more importantly have you checked!!)? If so where are you in the country or what country are you in?

I have raised this issue with the dealer and Volvo Canada, but don't honestly expect any feedback as they still haven't closed the issue I raised with them 18 months ago about B+ cable melting issue.

Neil.

Post by **scot850** » 27 Nov 2014, 16:40

I'm going to start a new thread only dealing with the rear sub-frame removal.

Neil.

Post by **mecheng** » 28 Nov 2014, 06:24

Hard to see from the pic, but can you weld it?

Post by **scot850** » 28 Nov 2014, 10:34

When I had the same problem with my 98 XC, I took it to a specialist welder (in oil country we have lots of specialist welders) and the were reluctant to try to weld it in-situ as too close to fuel tank, but also said all the aluminum in that area was crumbling, so weld would likely not take, and if it did, it would not be strong. I might take the old unit back to them and let them have a go, so if it fails no big deal.

Thanks for input though!

Neil.

Post by **FLXC90** » 28 Nov 2014, 10:44

Neil; if you can't get the subframe repaired, or if time is of the essence, Pick 'n Pull in Kelowna, BC has a 98 R wagon in their inventory. They listed it on 14 Nov, and the picture shows rear suspension in place

Good Luck either way.

Post by **scot850** » 28 Nov 2014, 11:48

Many thanks for the heads up on the Kelowna car. It is a 6.5hr drive from here and the snow is falling hard in the Rockies!

I have one being shipped from Vancouver Island on the west coast from a specialist auto-wrecker called Chapman Motors. Happy (parts guy) there has always looked after me and he says he has not seen the corrosion issues out there as they don't use a lot of salt in the winter if at all. Most of the parts they have sent me are like new. They are not the cheapest, but so far had no issues with the quality.

They have various 'R's and have just gotten a 2000 XC with 60,000 miles that was front end wrecked. It will cost $630 CDN with shipping (around $550 US). I reckon that with gas (even at $0.95/litre) is would cost me at least $100 + in gas plus and overnight (At least) to pull it. Plus the chances of having all the tools I might need are not good if I forgot something 6 hours away! The interior of BC also gets snow in the winter and they use a lot of salt in that area I'm told, so not worth the risk.

They also repair and straighten Volvos so know their stuff. Even the dealer here in Calgary uses them for used engines and tranny's for customers on a budget.

Still really appreciate you watching out for me!

Neil.

Post by **abscate** » 29 Nov 2014, 06:10

Good luck Neal

We use salt heavily here in NY, but my 1999 had minimal corrosion when I did all four corners of the suspension last summer. I wonder what led to that state...

Post by **scot850** » 01 Dec 2014, 10:20

Thanks for the feedback abscate. Yes this is kind of weird. The RH side of this car is showing only light crustiness on the upper edge so far at the same point. My 98 V70XC again was the reverse. I looked at 2 others in wreckers yards. One is a 98 XC and it was crumbling on the LH side at the same point, and one I saw in another yard, showed only the starting of the problem. Still wouldn't pay for the part as at that time I was planning to keep the car long term.

I can't think of anything I have done that would have accelerated this problem. Car gets washed regularly at the car wash with pressure jets (self wash). Otherwise the car just gets driven (not a lot, only 6000km in 2 years). Only other thing I can think of is they have started to use a new spray type de-icer on the roads here in the last 2-3 years, and I have noticed a huge increase in corrosion on exposed metal parts of the cars we own. Apparently concrete driveway layers, will no long warrant the concrete surface of the drives due to the corrosive nature of this stuff on concrete.

But is still begs the question why does it do it on one side more than the other?

When I get the replacement, I am wondering if I should powder coat the frame, and if there is something one can put between the aluminum frame and the steel to prevent this happening again? I know on older handmade cars back in the UK over many years you could get electrolytic corrosion between aluminum panels and the sub-frames of the vehicles steel.

Neil.

Post by **FLXC90** » 01 Dec 2014, 13:50

On airplanes, a standard procedure is to apply an epoxy sealant to the joining surfaces of the dissimilar metals and letting it cure prior to assembly. also, on assembly a thin coat of petrolatum (industrial grade Vaseline) is smeared in between to allow easy separation later.