940 turbo build thread

[Jfxv]

Having owned my brick for a good couple years now, I've learned a lot and fixed a fair few of its issues (on a shoestring budget and it's my daily, so often had to learn and do quickly as well). Nowhere near an expert, and plenty of others in the UK have done more than me. But for the sake of providing a resource for someone and getting it all written down rather than bouncing round my head, I figured I'd post it here. Pic uploader doesn't seem to be working properly, so will hopefully update once it's working nicely.

Quick history / spec list:
Bought at 143k miles ish in May 2017, having spent all its life in a field in Devon. Pretty scabby underneath. 1997 Volvo 940 LPT, completely stock. Interior was pretty good, wrinkly door cards and a few missing clips but mostly present and tidy.


First job was to replace the clutch and general service, this was one I had to get someone else to do as I had no time or experience working on anything mechanical. Turns out I should have put an uprated clutch in, and made sure the mechanic was reputable...

Prior to its first MOT with me, it then killed its fuel pup as I filled up right before taking it to its test. Had it towed home, left it there for a month or so while I went down to uni. Fast forward and in November I had it as my daily at uni (trading my alcohol, partying, and food budget for fuel money), and trying to keep it alive. Replaced a few things for maintenance, the cambelt and front oil seals being done in February (lovely job in minus temps). Replaced the distributor in April 2018. Finished out my third year in great fashion with zero fatal issues, and performed exceedingly well taking me and my mates on beach trips, pub jaunts, and the like.

Got it home, and set about putting an MBC and boost gauge in. Turned up to 0.85 bar and ran it for about 4 months like that. Clutch slipped a bit, thought to be due to the dual mass flywheel.
More oil leaks caused by using aftermarket seals on the front (definitely worth using OE Volvo seals). Rebuilt my brakes all round that summer prior to its MOT and went with EBC Ultimax (OE+ specs) on the front and stock pads on the back. New caliper on the front and reconditioned the others as best I could, eventually they all started working. New discs, new handbrake shoes. Now it stops brilliantly, and while they don't deal with fade amazingly, they're a great budget upgrade which doesn't count as an upgrade on the insurance. Noisy and dusty, but I don't care about that kind of thing.

Had a gaping rust hole in my passenger side sill welded as well,in the hope of getting it through its MOT first time.
It subsequently failed, but only on a handbrake imbalance and missing daytime running lights. Advisories on a windscreen crack, cracked number plate, and a few minor issues. But I got it through just about.

Back to uni for my fourth year, and had even less money this time around.
In November I realised upping the boost, while fun, also killed my 13c. Great opportunity to replace with a bigger spooly boi, so I got a used 15G from an 850. Had a bit of trouble getting the wastegate actuator we fabbed up to fit around the oil lines, so decided to run with an open wastegate until I could get a flexible braided line fitted. We also realised while we were replacing the oil and coolant that it hadn't been done when it was 'serviced' beforehand. Pretty frustrating, especially when it got to 1am and we still hadn't finished fitting the turbo. Few notes about this:

* The compressor housing and core both have to be rotated to fit a RWD engine. There is a snap ring on the compressor side which is a pain to get off, and the best pliers we could get for it were from a independent supplier in Bristol I found. The two sets I ordered off Amazon were both more expensive, ££££e quality, and the wrong size. Lesson somewhat learned...
* There are four studs in the exhaust manifold on a 90+ turbo manifold. There were two Inconel studs in the cast iron turbo exhaust housing. They wouldn't come out without excessive heat application with heavy hitting with a mallet, and eventually we decided to cut the corners off the flange with a grinder.
* Given the hassle we had getting the 15G with a conical flanged exhaust housing to fit, it would be worth going straight for a 16T with a straight or angled flange. Minimal extra hassle to get the downpipe to fit, and much better flow. Plus 16Ts are more readily available, and marginally bigger than the 15G.
* I reused the wastegate actuator from the 13c because it has a stiffer spring than the later turbos, which are designed to work with a solenoid rather than due to the gauge air pressure.

A slow few months ahead. I realised the core of the 15G was knackered, so ordered a brand new one from turborebuild.co.uk. Arrived quickly and the staff were great for helping me work out which one I needed, as the website listing wasn't the clearest. Meanwhile, I fitted the braided oil line. This was horrendous without taking off the oil filter relocation arm / oil cooler thing, but eventually I managed it. Had to grind, heat and bend a 19mm spanner to get it past the chassis rails and in to the banjo bolt on the block. Stubbornness as I refused to take the filter arm off, given that (I believed) the exhaust manifold would have had to come out to do that, and knowing my luck, I'd have sheared a stud or something. Another job completed in minus temps
Also put in some new front indicator lenses, replaced with clears. Looks much better!


Eventually got round to fitting the new core in January 2019, following university exams. Once again, I did this in cold conditions; there was a decent depth of snow on the ground around me, but this wasn't as bad as the other jobs. Reach in, pull the old one out, stick the compressor housing on in the right orientation, replace it. Done. Turned it up to half a bar and enjoyed turbo noises again. Also put some Toyo T1Rs on the rear, as the old tyres were a bit perished.


Due to requiring ankle surgery in February and therefore not being able to drive for a few months, progress stalled. Realised my heater core and heater control valve were leaking in March, so these got bypassed with a copper pipe, sealing tape and hose clamps in the engine bay so it could be driven without losing all my coolant. I also designed and 3D printed a boost gauge holder, and moved my boost gauge back to within my eyeline. It had previously been in the radio slot, having replaced the radio with more suitable in car entertainment.


Once back on my feet, got back on with things. Took the back box with its daft S bend tailpipe off and left it that way for a bit, while I made up a 304 stainless 3" straight pipe for the rear end. Used a 'reducer' to adapt from the diameter of the over axle bend and took it out to just inside the rear bumper. Sounds great and although it's a bit rice, I like it. Also sorted out a minor advisory from the previous MOT by doing that, which was obviously my reasoning for doing so.


Then I put in a V cam, as I'd noticed another oil leak from the camshaft seal. Turns out the original T cam had a slight groove on it and was weeping past the (admittedly crap) aftermarket seal. Now revs up nicely, fuel consumption is even worse, and I love it. Whacked the boost up again to 0.7 bar, will go higher sooner or later. Also plumbed in an eBay catch can inline with the original PCV separator box, and using the original vacuum source from the pre turbo intake pipe.


That's pretty much it on the performance side, as it's just failed its MOT again. This time, on one thing only! And only three advisories, a new record!
- Rust hole in the passenger side rear by the jacking point, courtesy of not cutting out all the rust when the sill was previously welded. Thanks to the welding guy for that one...
- Windscreen crack, from last year. Not a failure as it's right on the other side of the screen and doesn't obscure anything.
- Oil leak, coming from somewhere strange. Looks like it's dripping off the aforementioned coolant hoses bypassing the heater core. Definitely a weird one, but I'll accept it as it's a 22 year old car now.
- Front exhaust mount broken. This was a recent breakage, I'd noticed it was bodged together when I replaced the turbo. Started rattling only a week ago. I'll sort it when I sort out a new exhaust.


Tl ; Dr:

+ 15G at 0.7 bar
+ V cam
+ Upgraded front brakes, reconditioned rears and handbrake.
+ Everything works in the interior, including sunroof. Only things that don't are the rear washer and headlight wipers, which have been removed.
+I estimate I get about 25mpg on average, not bad considering my driving style and I drive through town a lot too. I think I only got 28mpg when I first got it at 135* bhp, it's now running just shy of 200* bhp I'd say.
* compared to factory figures.
+ minor visual upgrades - it's decent paint underneath but has scratches all over, so touched up a few bits where it's flaked off. A few stickers, and prancing moose badges. Painted my front grille black, and replaced the headlights and front indicators for a pretty clean look if I do say so myself.


Upcoming plans:
+ Lowering springs and GAZ adjustable dampers
+ possibly an adjustable panhard rod from Viking Fabrications
+ KL Racing intercooler
+ 3" 304 stainless exhaust from turbo back, going to switch to a straight or angled flange housing for this.
+ Replace my heater core and control valve (Now rocking horse fecal matter as it's a non AC model) with an electric setup
+ e-fan and the bigger stock radiator to go with this
+ Wasted spark conversion
+ Hoping to do some LH2.4 tuning too, once I pull my finger out and get a wideband, Ostrich, and some blank chips. Way too many ideas for my own good to be honest

And down the track I potentially have a B5234 T5 engine to go in. It needs a rebuild though, and instead of making it work with the M90 I'll probably go with a BMW 330d gearbox or something. Need to research this all more, but my perfect car is a RWD brick with a turbo 5 pot, so it's a pipeline idea.