More cooling system corrosion

The aluminum coolant passages on the B280 are in great shape, which isn’t exactly a surprise with such a low-mileage motor. Once I replaced the split water pump I reassembled it with a new thermostat and had it ready to go and was feeling good. As I was test fitting the radiator and hoses recently I noticed there is a tiny difference between the two thermostat housing outlet diameters. Which is pretty obvious here with the B28 setup on the right and the B280 on the left.

For some reason the B280 has a much smaller diameter outlet than the B28F did or the Eagle Premier 3.0 does. Maybe the smaller outlet combined with the higher pressure overflow cap in the 760 cools better than the B28 setup did? This goes beyond my knowledge of cooling system design. But since I am using a 260 radiator and 260 radiator hoses I need to replace that outlet with the bigger one. Easy job. And since I have one lying around why not use the nice Eagle housing with its fancy plug wire retainer? Looks nicer in my opinion.

Only downside I can see is it needs more aluminum corrosion cleaning, which I’ve become rather practiced at thanks to the Mercedes.

After a half hour or so of wet sanding the bulk of the corrosion is gone but there is still quite a bit of pitting.

Another hour or three of work and I’m almost ready to say it is good. Minor pitting left but not much that I can really feel with a fingernail.

The flange on the water pump side is pretty good. Some light corrosion but nothing too bad. I used a piece of glass with some value lapping compound to clean up the bottom some while still keeping it flat.

And then it went back on the motor and I’m ready to continue with assembly.

Aluminum corrosion

The aluminum thermostat housing and related tubes on my original motor were in terrible shape with major pitting and corrosion, but fortunately the ones from the replacement motor are much better. I still spent some time cleaning them up. I’m not exactly sure why, but these aluminum parts tend to corrode more often and more dramatically on Mercedes than any other car I’ve worked on. Not sure if it is the type of aluminum, the type of coolant used, the change interval, something else, or all of the above. I do know the coolant in the car when I got it had not been changed in a while, so that certainly contributed.

On the left is my original thermostat housing and the cleaned up replacement is on the right. The corrosion on the original was bad enough I was worried about leaks or tightening a clamp too hard and breaking it. First I cleaned with degreaser and soap, then with brass brushes by hand and dremel to eliminate the powdery white corrosion, then a scotch-brite pad to get the rest off. After that I wasn’t happy with the amount of pitting of the aluminum so I sanded the areas where the hoses clamp down to eliminate some of it. There is still some decent pitting but I don’t want to sand much farther and make the material too thin. I put a light coat of anti-corrosion gel on, wiped most of it off, and called it good. Maybe this all will help, maybe it just makes me feel better.

New thermostat installed and a new silicone bypass hose from the thermostat to lower water pump hose. Getting to that hose is such a pain I don’t want to do it again if I can avoid it. A $7 silicone elbow cut to size should do the trick for as long as I need it to last. Or longer.

From now on the car should get proper G05 or Mercedes coolant changed at regular intervals and I’ll check on the aluminum and see if it continues corroding or not.

Wood in cars

I put the bertone door panels in my car many years ago and have conditioned the leather a couple times a year but otherwise haven’t touched them. Recently someone else noticed the veneer panels are looking a little faded and could use some cleaning and oil to keep them in shape. It had not even occurred to me that someone could or should be done about them. I had assumed they were covered in a thick clear coat but in fact there isn’t much finish at all on them and it looks to be just an oil finish.

So some cleaner and a coat of mineral oil later and they are looking much better. As they were on the right and after cleaning and oil on the left. As always it is the little things that really make a difference.

Snabb intake upgrade

Last time the 850R was at the shop they noted that the factory intake pipe from MAF to turbo was on its last legs and needed replacing soon. Which sounded to me like a great excuse for an upgrade. The stock pipe is an accordion type plastic hose and is a slightly smaller diameter than the turbo inlet. That combo makes it a little restrictive. Not the most restrictive part on the car but still an easily eliminated restriction.

Here’s the stock intake pipe angling down from MAF to the turbo.

Choosing between the do88 hose and the snabb pipe and hose was difficult. Both seem like good options and I have been very happy with all the do88 products I have. And I was very concerned how much the polished snabb pipe would stand out in my engine bay. But I decided to go with the snabb pipe because long term I figure it will be easier to replace the silicone connectors if needed than to replace the whole silicon hose.

First step is to remove the plastic factory pipe and then cut the ptc valve grommet off and shave down the lip at the end of the valve so it fits in the snabb pipe.  Quick work with a razor knife and a dremel and some sandpaper. Then figure out its orientation and clamp it in place. And that of course is the hard part.

Here are the two setups side by side. Though I left the plastic bags on the new silicone connectors and that looks silly. The reducer on the top connects to the turbo, the ptc (intake heater) goes in the bung with the short silicone hose, and you can see two of the three total vacuum ports on the snabb intake. Of which I only needed one so two are capped.

Once the ptc is in the snabb pipe just align the pipe, connect all the houses, and tighten them down. And that is the hard part. It took me probably an hour making small adjustments to get the pipe to an orientation where nothing rubbed. The relocation of the ptc valve puts it very very close to the stock wastegate on my 15g.

And there it is in place. A little more obvious than I would like, but not too flashy.

The whole process would have been only a few hours except partway into the job after modifying the ptc I realized I did not have a tool for the oetiker clamps on it. Fortunately Amazon Prime next day solved that problem. And I was able to use the extra time I had to replace the cbv and tcv vacuum lines with silicone hose from ipd. That is a lot easier to do with the airbox out of the way.

Driving impressions have been brief so far. Low end power certainly seems improved, but to be fair this car has everything except the stock intercooler pipes upgraded. The sound of the turbo spooling up is a little more prominent now, without being annoying. So far so good. And the quality of the intake components is very good. Should not have to worry about this setup for a long long time.

Functional fogs

Well, sort of. Factory fog lights on 850s are more cosmetic than functional. But the single most annoying thing about them is that they do not turn on unless the low beam headlights are on. Which is a little frustrating because if it gets foggy enough to need fog lights then the low beam headlights are causing glare when on and the fog lights are not that helpful. This seems to be a feature for the US or North American market cars. The European market cars work in a more logical way where the foglights can be turned on if the parking lights are on but the headlights are off.

I especially want mine to work like the European cars because my driveway angles up to the street and so when I pull out at night my low beam lights shine right in the windows of my neighbors across the street. Not cool. So I’ve taken to rolling out the driveway with just the running lights on and turning the headlights on when I am fully on the street and not pointing at any houses. Which means I’m hard to see if a car is coming and it means if there is something dark on the edge of my driveway I might not see it. Easy solution is to use the foglights alone. They light up the driveway well enough that I can see and be seen but they don’t project far enough or bright enough to irritate my neighbors.

Fortunately the change is really easy. The fog light relay under the dash (#213) is not so much a relay but more a jumper that powers the fogs. The jumper just needs to be rotated around and put back together looking like this.

And viola, foglights that can be turned on with the parking lights only.

It is the littlest things that make the biggest impact sometimes.

AW71 accumulator mod

Though the AW71 should be able to handle all the power the B280F makes and more as is I decided to shim the accumulators while it was out of the car and relatively dry. More because if I’m going to do it now is the time rather than feeling a need to do it. But unless I screw something up doing it won’t hurt anything and could be necessary later. 

This modification has been pretty extensively documented so I won’t re-hash all of that here, but basically the goal is to keep the transmission living longer by reducing the slippage of the plates caused by the slow soft shifts that are comfortable to a driver. We do that by making the transmission shift faster than it would otherwise. Not sooner, faster. Three accumulators under the valve body control that speed. They are pistons with o-ring seals moving in a bore with a spring and a vent hole behind them. The transmission fills the cylinder with fluid which pushes the piston down in the bore reducing the pressure available to the shift. Fitting a solid spacer inside the spring stops that piston from moving and means full pressure is available much faster. 

This is my first time playing around in the guts of an automatic transmission and has been interesting. It is intimidating at first. Here the filter screen has been removed and the valve body is still in place while I gather my courage. 


Once the valve body is removed and the kick down cable detached this is under it. The three accumulators are in the top right. A light puff of compressed air into the holes at the base of the bores pops the pistons out. 


Now to create some shims. I had trouble finding any solid rod locally so I used the shank of some large bolts with the head and the threaded portion cut off. I made the shins about 3/16” shorter than the springs so there would be a little movement but not much. 


Here is a shot of the rearmost accumulator reinstalled with the spacer and the front two still out of their bores. 


When I pulled the AW71 from the 262C I had been intending to replace it with a manual transmission so I frankly wasn’t paying much attention to what it was like. Which is a bit unfortunate now that I am planning to put it back in. I’m not sure how many more seals I should replace. I don’t recall it leaking much fluid, but I also wasn’t paying much attention. 

B280 oil and water

I have not given up on the Bertone project. Though it is admittedly hard to tell due to the lack of progress. Today I used a vacation day to get some work done.

The replacement b280F has been sitting for the better part of a decade so I am replacing some of the more common seals and hoses that fail without going crazy and ending up rebuilding it. The front and rear crank seals have certainly been seeping so those are on the list. Took care of the rear one today. My first crank or cam seal replacement. Hopefully all is correct. Oil and grease on the crank surface of the seal and gasket dressing on the outside. New housing gasket and I wasn’t sure what to do there so I went with hylomar.


The old water pump was an original PRV one and the impeller was rusty inside and the outlet pipe was cracked so I replaced it with a new GMB pump. The GMB pump looks pretty decent quality but the original pump is very well built. And very nicely all the bolt holes are open to the rear so getting some penetrant oil on the threads is simple. Hopefully the lack of that feature on the GMB pump does not bite me in 5-20 years. Also I haven’t used this style of pump where the oump housing is re-used before. Interesting. 

Reassembly of the pump is waiting on some silicone hoses from Amazon of all places since I don’t want to wait and get them from my normal suppler, Premier Rubber in Portland. 

C70 rear subframe brace

The rear subframe brace from a c70 convertible fits the front wheel drive 850/70 series cars, so I decided to install one and see how it affects the handling and ride of the 850R. Aftermarket companies makw chassis braces that work in a similar way but why not have the one Volvo made to reinforce the car once they cut the roof off? Unfortunately they are low on the car and most junkyard forklifts will damage them lifting the car so finding a good one can be tough. And they are heavy. These are not lightly built.

The brace connects both of the engine subframe rear mounts to each other and the body. It is the large U-shaped oval tube in the photo below, as seen from the front of the car.


Installation is a fairly easy job once the car is in the air. Unclip the rear O2 sensor wiring retainer from the under exhaust cross-panel and remove the four 12mm bolts to remove the panel. You will re-use these bolts to install the brace. Support the rear of the engine subframe and remove the big 18mm subframe bolts on each side as well as the two 14mm nuts that attach the brackets. You won’t re-use the brackets. You will need to replace all 6 of these bolts with c70 convertible ones, which are longer. The subframe brackets and under-exhaust cross-piece are not re-used, the brace takes their place.

Installation is the reverse of removal and not too hard. I found it easiest to thread the big subframe bolts on enough to hold and then attach the rear cross-piece under the exhaust before coming back up to install the 14mm bolts. Torque the subframe bolts down and remember to angle torque the two big ones. 77ft-lbs plus 120 degrees for the big ones and 37 ft-lbs for the small 14mm headed ones.

These is a chance the subframe will shift during install so an alignment may be needed.

C70 convertibles also got a reinforced engine subframe and aluminum subframe bushings but since those are much more difficult to install they will sit until I happen to have the engine out for some reason.

Driving impressions and a report on how often the brace scrapes speedbumps to follow. It is low on a normal car and very low on a lowered car like mine.

do88 Intercooler again

I ordered a do88 Intercooler for the 850 when I bought the one for the 240, but I delayed installing it now because I was planning to do an aluminum radiator at the same time. I thought I should probably wait until I do a manual swap so I don’t have two empty plugs for the transmission cooler, and what if I go with the later oil pan with the integrated oil cooler and don’t need those either? So I decided to install just the Intercooler now and worry about the rest later. Honestly if I knew then what I know now I would have just waited a while longer. Replacing the radiator/intercooler on an 850 is not difficult, but it certainly is complicated enough that it is not something I want to do again. Halfway through the install you will be considering buying a 240/740/940 turbo instead. The 850 Intercooler is bolted to the radiator which is bolted to the car itself, so the easiest way to replace it is to pull both of them out through the bottom.  Which requires a fair amount of room. More than I thought I would need when I put the car on jack stands. And removing a ton of hoses and lines and plastic trim and relays and so on.

The intercooler itself looks good, though many of those fins look a little mangled.  Other that that it looks like a high quality unit like the 240 one. I am hoping for an improvement as pronounced as what I noticed after installing the 240 one.


After a couple of days working on it and miscellaneous other small things that cropped up the intercooler is in place and there are no air/coolant/oil/atf leaks after running it up to temp once.


Well, mostly in place. The biggest issue I have that I know of right now is that somehow the radiator/intercooler package is farther toward the back of the car on the top, so the plastic trim panel that mounts the fan relays can not be screwed into its holes in the body. Which is annoying at the least. I’m not sure what to do about it. Even loosening everything to try and push it forward didn’t help much. I’m not sure if it is supposed to fit that way or not. For now I will monitor it and see what happens. I would absolutely buy products from do88 again because they work great but I am irritated by the use of words like “drop-in” because frankly they haven’t been and instructions are lacking. Of course this could just be something I did wrong and haven’t figured out yet. It is really bothering me, so we will see how it goes.


I will need to get back in there eventually. My AC condenser is very beat up on the bottom few inches and I don’t see how it can be flowing much air through that portion of it. So some day I am going to need to replace that. Which, you guessed it, requires removing the whole radiator/intercooler package again.