my first MB, 1986 190D 2.5 NA diesel - PeachParts Mercedes-Benz Forum

weird beard · #1 07-13-2010, 04:56 AM

my first MB, 1986 190D 2.5 NA diesel

I have been lurking several MB forums and this one looks like the best. I just picked up my first MB. It is rough but not beyond all hope. Being a diesel mechanic by trade, picking up one of these was only fitting. I just need to do some quick rust repairs to the floor and rockers, change one more tie rod end and it will be technically fit for the road.

It has 2 concerning problems. The first is with the Climate control. It has been Macgyverd to not work by the PO. No heat from the center vents, heat all the time from the outter and defrost vents. Temp control inop. the blower is on a toggle switch. I pinched off the heater line for now but the outter and defrost vents still blow hot? From what I have read, there is supposed to be a temp sensor inder the cluster betwseen the idiot lights? is this correct? if so it is missing. The A/C has been converted to R134A, and it has a full charge, The compressor however does not come on. Luckilly it is not siezed! I'm searching the forums for info on this system, but most of what I can find are specific questions for specific problems. This one is so far gone I need to know details about the whole system so I can get it working again. Wiring diagrams and component locations as well as how it should work and common failures would be great. I have no problem rewiring the entire system, or ripping it out and making it a manual one.

The other info I am looking for is on the automatic trans. The car seems to rev too high on the freeway (tach inop so don't ask how high) It appears to only be shifting through 3 gears. The shifter shows it being a 4 speed (D, 3, 2) Shifting manually through the gears, starting by dropping into 2, it apperas to be staying in first. Shift up into 3, it shifts into second. shift into drive, it shifts into 3. Shift into neutral, it shifts into neutral. shift back down, it downshifts. maybe I'm wrong on the shifting, but it really seems to be running out of gears and is not going into overdrive (do they have overdrive?) upshifting and downshifting through the gear selction makes noticable gear changes each time, but appears to have only 3 gears. Tranny failed, wrong one or needs adjustment?

any help would be greatly appreciated. Until later, I wsill be searching these forums fior the answers!

layback40 · #2 07-13-2010, 06:15 AM

weird beard,
Welcome to the forum!!
I cant help you with your aircon, but for your trans question, your speedo should be marked with the change points under full throttle. Have a look, there are little marks, 1 mark for first to second, 2marks for second to third & 3 marks for third to fourth. Its not an overdrive trans. My 250TD has the same motor & trans as yours I think, its happy at 70 mph on the highway, doesnt sound like its screaming, the tach dont work, will get to it one day. I guess it depends what ratio your diff is.
Hope that helps a little.

shertex · #3 07-13-2010, 06:18 AM

Check your owner's manual to confirm, but but I'm pretty sure that when climate control is in heating mode the air flow is not designed to come through center vents.

babymog · #4 07-13-2010, 09:42 AM

The rectangle between the idiot lights is an outside-temperature display. Normal failure mode for this is for the LCD to leak, eventually turning the display black.

You likely need a new CCU/climate control unit (the pushbutton unit). It will burn up if the aux pump draws too much current. The aux pump is a small electric pump that pushes water through the heater core, hot wire it to see if it even runs. If it draws too much, un-plug it until you can find a new one or you will burn up the next CCU. The fan switch is separate, but also a common failure item, speeds are controlled by a resistor pack near the battery IIRC.

For the shifting, check two things: There is a switch (downshift button) under the gas pedal on the floor, un-plug it to see if it was sticking and preventing shifts. If that is not it, check the "bowden cable" or downshift cable leading from the throttle linkage to the transmission, it should move in/out easily and return to rest when the linkage is at idle. If neither of these are the problem, check fluid level, but it might be the downshift solenoid sticking.

weird beard · #5 07-13-2010, 12:56 PM

Okay this helps quite a bit.

Is the auxillary coolant pump how the vent temperature is controlled? Mounted in the engine compartment inline with the heater hoses?

I was wondering what the marks on the speedo were for. The bowden cable is not sticking, what should the adjustment be on it? I never even knew there was a switch on the floor for at the throtle. Is the downshift solenoid easy to get at?

Thanks alot. Back to work on the old girl!

It may just be a clapped out entry level Mercedes to some, but It is giving me something to do. My new hobby. I restored a 1981 Honda CB650 over several years. When it was done I lost interest in it. This car can always be better. There is always something I can do to it to improve on. It should take a while before there is nothing to do and I get bored.

bigblockchev · #6 07-13-2010, 12:58 PM

Hi and good luck with the 190. The trans starts in 2nd & will not downshift into first without the forementioned switch working properly. So you will not ever see first gear unless you mash it hard, thus the appearance of only three gears. There is no internal connection from the centre vents to the heater core they are only connected to the cooling coil of the AC ( you can see the AC core through the opened vent flaps) so no heat ever through them. The Ac compressor can be tested by jumpering out pins on the Klima relay behind the battery. You will have to do a search to find troubleshooting info on that but it is rare to find a CCU that still works , most have been killed by the aux water pump. I have had 5 190s and none have had a working CCU. Cheers Dan

babymog · #7 07-13-2010, 01:03 PM

The 190D 2.5T starts in first all of the time, is there something different in his '86 NA?

weird beard · #8 07-13-2010, 01:14 PM

if working ccu's are non existant, what do you do? Just rig something up? Thanks for clarifying the vent function.

babymog · #9 07-13-2010, 02:35 PM

They're in junk-yards, I might even have one left from my 201 days. Shouldn't be hard to find.

If it has a spot on the plastic underside that looks like it is partially melted, it's probably not good.

Aquaticedge · #10 07-13-2010, 03:10 PM

Quote:

Originally Posted by layback40

weird beard,
Welcome to the forum!!
I cant help you with your aircon, but for your trans question, your speedo should be marked with the change points under full throttle. Have a look, there are little marks, 1 mark for first to second, 2marks for second to third & 3 marks for third to fourth. Its not an overdrive trans. My 250TD has the same motor & trans as yours I think, its happy at 70 mph on the highway, doesnt sound like its screaming, the tach dont work, will get to it one day. I guess it depends what ratio your diff is.
Hope that helps a little.

Is this with the pedal to the floor and the kickdown activated?

weird beard · #11 07-14-2010, 03:02 AM

Okay, I got the tranny figured out. Thanks! Bowden cable was out of adjustment. It is in fact taking off in second gear (take note of this 2.5 NA diesel owners, the tranny defaults to 2nd gear take off). The cable was so loose it never saw the need for first. I tightened it up and now I have 3 shift points! Wow! what a difference. I thought the trailer hitch on the back was some sort of cruel joke, now it actually gets up and moves. I installed the new exhaust today, man, it is pleasent to drive. The sensation of reving too high on the highway was due to the rotten exhaust, it just puuurrrs now.

Must do list is shrinking. Just down to body work - floor patches and a temperary rocker repair. I have a deadline to get it on the road so the rockers will have to wait do be done properly.

Out of curiosity, are there affordable rocker repair panels available or does one just make their own?

After it is on the road list:
-source a new CCU and get the heater / ac working
-I have to do something about the trashed dash
-repair door and trunk locks to work

which brings up two more questions:
How do you get the cluster out?
Has anyone here developed some crazy ways to make the dash look presentable until I either gat a dash cap or find a good used one? Silicone the cracks over and paint it with black liquid rubber?

babymog · #12 07-14-2010, 11:43 AM

Cluster pulls straight out. I've always removed the left vent to give enough space to get my arm in, and hand behind the partially-removed cluster to un-screw the speedometer cable.

Jer · #13 07-14-2010, 11:46 AM

Congratulations on your acquisition of a Baby Benz!

In case you don't already know, the central locking system is pneumatically operated. It is a very reliable system, but when you have problems, it's usually because of vacuum leaks through the tubing or the vacuum elements in the locks. Sometimes the pumps go on the blink.

The instrument cluster is removed very easily with special hook tools that you can make or buy. Make sure you unclip the speedometer cable from behind the driver's floormat. There are a bunch of connectors on the back of the cluster, plus the speedo cable, that will need to be removed.

weird beard · #14 07-15-2010, 05:09 AM

Got the floor panels welded in, car has been safetied. Permanent rocker panel repair will follow once I get the dash fixed up.

I have less than $700 invested in this car, including the purchase price and tax, and by the end of the week it will be fully licensed for the road. I have been taking quite a ripping from my co-workers about the car because it is a bit rough, but once I'm done, it will look great. Best of all, I can do most of the repairs for almost nothing. The floor patch was recycled steel, for example.

sasquatchgeoff · #15 07-15-2010, 11:57 AM

Welcome - my NA 2.5 has been a joy. Lots of work though. Lots of dash toppers online, but most are so-so in appearance. Look for a new dash at a junkyard, or maybe one of our friendly 201 owners here has a spare. They are fairly expensive to ship. Here in OR, there are many 201's in the yards.