what would you do?

[jonnyboy]

hi all.
As some of you will know I bought a project r129 300sl 24v a few weeks back with a suspect head gasket amongst other things. The car came with a head set in the boot and some stem seals. Ive done 3 head gaskets in the last 4 years but had very little to do with twin cam engines. The car has done around 136k miles, doesnt seem to overheat, and as yet I don't know if it uses any oil or water as I've only done 5 or 6 miles. Its symptoms were rough running and being hiccy and farty.

I have the chance of a local to me engine and box from, i think, a member who wants £300 for them, but there was no significant testing of the engine prior removal as the car was bought as a donor and immediately scrapped.

I have a competitively-priced labour quote to do the gasket, inevitably these things usually lead to more parts along the way and I have an inherent need to keep costs low and do as much as I can myself.

These are the compression test figures I did last night:-


Cylinder Dry Figure Wet Figure

1 15.5 16.25
2 16.25 17.00
3 12.25 13.00
4 12.75 13.25
5 13.25 14.25
6 15.5 15.75

Figures are in bar, the wet figure is the same test with a few drops of oil dropped into the bores (to temporarily seal worn rings). The top breather is a bit oily. There is no significant rattlyness from the top end. No back pressure to speak of so hopefully the valves and guides are ok. I am sourcing a header tank "sniffer" although struggling at under £85 right now. Tried a header tank "bubble test" in the meantime which was inconclusive as I kept getting spill-over out of the header tank with no bubbling at all .

Plugs weren't too bad, none rusty, or wet:-

IMG00020-20090903-2027.jpg picture by entire54321 - Photobucket


Sorry for the long post guys.

Interested to know who would do what, and if anyone has done an m104 twincam, how bad it was etc?

 

[Will]

Personally, I'd strip the head off and look to do that first. If it turns out that there's other complications once the head is off, you're no worse off that you'd have been when you were looking at complete engines.

Best case - might just need a clean up and a new CHG

Worst case - you've learned how an M104 comes apart for nothing

Will

 

[lynall]

If youve done hg before the m104 is not hard at all, i did the wifes on the driveway.

I would also do a search/google for merc wiring looms.

Wifes old 104 was fussy on spark plugs and seemed to eat them every few months, not the fancy ones which it ran crap on just the common std plugs which it seemed happy on.



Lynall

 

[lynall]

Wire harness probs PeachPartsWiki: W124 Engine Wiring Harness Replacement

 

[lynall]

Head gasket PeachPartsWiki: Head Gasket Replacement

 

[jonnyboy]

thx so far.

i bought a h/g "sniffer" which detects co2 gases in the coolant, cant get any steam out of the header tank to use it right now though
interesting that whilst cylinders 3 4 and 5 are down, they are all around the same figure.....

Lynall, your wife's m104, I presume thats a twin cam 24v ?

 

[EDZ649]

John, I'm one for keeping things original, especially if the car is a genuine example with full service history. I would repair the existing head problem, at least you know the rest of the mechanicals should be ok

 

[Druk]

There's no evidence these 300 24v 104 engines suffer from the dreaded loom problems. 280 and 320 HFM but not 300s.

I wish Merc had given the later HFM M104 engines a different designation (M105?) to distinguish them from the K Jetronic ones. What a bother that would have saved over the years.

 

[d w124]

Wire harness probs PeachPartsWiki: W124 Engine Wiring Harness Replacement

That`s great info,but he has the early M104 300-24V so the loom is not a prob.Something like this Mercedes 300E 24v. Breaking for spares. on eBay (end time 04-Sep-09 20:37:47 BST) would have been nice and still make some money by selling some parts.

 

[alexander patie]

There's no evidence these 300 24v 104 engines suffer from the dreaded loom problems. 280 and 320 HFM but not 300s.

quite true.

compressions, although varied, are fine; not indicative of any trouble. were they done with the throttle open? should be, can make quite a difference.

johnny, you problems are the rough running and hickups and farts? unlikely to be mechanical faults. suspect the entire ht system including plugs, especially the dist cap and arm; check for damp in here! also suspect the metering head and ecu power supply.

 

[jonnyboy]

That`s great info,but he has the early M104 300-24V so the loom is not a prob.Something like this Mercedes 300E 24v. Breaking for spares. on eBay (end time 04-Sep-09 20:37:47 BST) would have been nice and still make some money by selling some parts.

couldnt agree more but it was 10 hrs away by car, and it hadnt been turned over in 3 years. hummed and ha'd a lot about that one...

 

[jonnyboy]

quite true.

compressions, although varied, are fine; not indicative of any trouble. were they done with the throttle open? should be, can make quite a difference.

johnny, you problems are the rough running and hickups and farts? unlikely to be mechanical faults. suspect the entire ht system including plugs, especially the dist cap and arm; check for damp in here! also suspect the metering head and ecu power supply.

test done with throttle open and 10 revolutions each cylinder.
it "smells" like its running a touch rich to be honest.
i bought a cylinder head "sniffer" and tried a test yesterday - couldnt get any steam up from the header tank to test it
getting weirder and weirder

 

[lynall]

Yep was 24 valve m104 changed hg due to the coomon leak offside front of the block and messing up my then new driveway.

Good engine apart from that and its habit of new spark plugs every couple of months.

Heads a pretty hefty lump, remember toughest bits were getting manifold to ex bolts undone for some reason and the little pin on the front of the timing, case got it out using an m6 bolt and various washers and sockets as spacers.

Porbably best to do a decent run then test when you get home, wonder who diagnosed the problem?

Lynall