Lower Thermostat Housing Replacement - 1998 V70R

Post by **scoobycant** » 01 May 2009, 11:00

I ruined my lower thermostat housing while trying to extract a broken bolt. Seems like I have to remove the power steering pump. Any words of wisdom from someone who has done this repair? Specifically, what is the liklihood of the 3 Torx bolts being seized? Car has 150,000. Thanks for any information.

Post by **Ozark Lee** » 01 May 2009, 15:00

Welcome to MVS,

I have not yet had to replace the lower housing but I do believe that the power steering pump has to come off to get to it. The torx bolts are notorious for stripping and Volvo finally woke up and they have coated steel replacements. Get all new bolts, they are normally under $1.00 each at the dealer.

Letting the old bolts sit with a good shot of PB Blaster overnight will help and the better the torx bit the better of your chance of success.

...Lee

Post by **MadeInJapan** » 01 May 2009, 17:47

Don't forget to buy the gasket for that lower housing... Here is a friend of mine's experience with the same issue you're having:
http://volvospeed.com/vs_forum/index.ph ... pic=109612
Look on page 2...that that tool he did everything without having to take the power steering pump out.

Post by **scoobycant** » 01 May 2009, 19:52

Thanks very much for your posts. I've been spraying with PB Blaster for 2 days now tryin' to build up courage if you know what I mean. Got the new Volvo bolts. Lower housing and gasket on order. Went to Sears and bought 3 new Craftsman T40 bits (one per bolt

). Just read your posts tonight. I ordered the xtra-long T40 from Toolsource. Gonna try the repair without removing the ps pump. Thanks a bunch for that forum link. Here's an online source for the xtra-long T40:

http://www.toolsource.com/xlong-torx-dr ... 51192.html

Post by **scoobycant** » 02 May 2009, 07:06

OK, change of plan. Decided to remove the ps pump. Sometimes best to look the enemy in the eye when it's a life or death situation

. Still will need the xtr-long T40 for the bottom bolt though. There's not enough room for my 3/8" extension. Can slip her through but not at the exactly right angle.

If the patient lives, I'm thinking about using stainless steel socket head cap screws for the rebuild and avoid the Torx fasteners altogether. Interesting discussion at http://www.finishing.com/271/67.shtml
regarding Aluminum/304 SS galvanic corrosion. Not ready and willing to bet the farm on the new Volvo bolt coating. New Volvo bolts not looking magical to me at this point. Maybe I got old stock, but the finish on the new Volvo bolts look remarkably similar to the ps pump bolts that I just removed.

Anyone have any info about using stainless steel fasteners and aluminum threads? Thanks in advance.

Post by **MadeInJapan** » 02 May 2009, 12:21

NO problem- go ahead with the stainless as long as the threads are the same.

Post by **vegasjetskier** » 02 May 2009, 14:14

You should be OK since stainless is only a few lines away from aluminum on the galvanic chart: http://corrosion.ksc.nasa.gov/galcorr.htm

Post by **scoobycant** » 05 May 2009, 09:12

Thanks for the info. The 3 bolts that hold in the lower thermostat housing are M7 x 1.00 x 30mm. These are the same as the 2 bolts that fasten the top housing to the lower housing.

M7 seems to be rather uncommon in the US. Ordered 304 SS socket head cap screws from Stig Fasteners at http://www.a2stainless.co.uk/aboutus.aspx.

2/3's of this nightmare is over - successfully got out the 2 top bolts that fasten the lower housing to the block. Have to wait on the 3rd, lower bolt though until my xtra long Torx tool arrives.

Post by **scoobycant** » 07 May 2009, 10:57

Xtra-long T40 bit arrived yesterday. Looks like a nice, high quality unit. A little too heavy duty, however, as the shank hex is too large for the available room. The tool binds between the top of the aluminum casting that supports the alternator and the bottom of the lower thermostat housing. I don't have a lathe, so I guess I'll resort to either my bench grinder or my Dremel tool with diamond cut off wheel. Bit is made of S2 steel - the sparks should be beautiful

!

Post by **scoobycant** » 08 May 2009, 07:23

Grinding wheel worked nicely. I had to reduce the business end of the shank about 3-1/2". 3rd, bottom bolt came out without a fight, just like the top 2.

Put everything back together. Drove about 30 miles last night. Didn't leak. No drips under the car this morning. Will replace the 2 upper housing bolts with 304 SS ones when the arrive.

Thanks again for the information provided.