|03-04-2009, 09:44 AM||#1 (permalink)|
Cylinder Head - Valve Guides
I have a 1988 260E with 190,000 miles on it. The engine developed a miss, and I discovered no compression in the #6 cylinder. Upon removing the cylinder head, I found a burnt exhaust valve. My question is this - How much wear is normal in the valve guides? I'm going to replace the valve seals, but there seams to be a little bit of *slop* - for lack of a better term - in the valve seals. Is this normal, or should they be tight? If I do opt to replace the valve guides, can you knock them out, or do they need to be drilled out? Any advice would be appreciated.
07 C280 4MATIC 80k Miles
00 E430 4MATIC 74k Miles
88 260E 201k Miles
|03-04-2009, 11:27 AM||#2 (permalink)|
Date registered: Nov 2006
at 120,000 miles, i had my motor rebuilt in norder to turbo charge it. All the valve guides wre worn, and i had them all replaced, this was on a 103 12v engine with amg mods.
i would expect your guides to be worn, and if one valve is burnt out, i would suggest that you bite the bullet and have the whole job done at onec, wich will reduce costs in the long run!
"mutty" 'der nail'
soon to be a six speed nail
only do the mods others tell you to, otherwise you will be in trouble
all mods, even those that are almost identical, were not created equal, you risk turning your car into a ricer if you dont follow the crowd, you have been warned...
it is obviously correct that if your car aint shiny, your opinion doesnt count
|03-04-2009, 11:51 AM||#3 (permalink)|
Date registered: Jul 2005
Location: Long Island
Last year I had the head rebuilt on my 234,000 mile '88 300E and just a few weeks ago on my wife's 114,000 mile '89 300E. In both cases there was oil consumption due to the guides being worn. These engines have inherently soft guides so I would plan on replacing yours as well.
Not having any understanding of your qualifications I couldn't comment on whether or not you should be attempting this yourself. I personally don't have the equipment or experience and therefore trust the machine shop work to an experienced professional when a cylinder head needs serious or even routine attention.
I will say that you should consider replacing the hydraulic lifters, and having the head skimmed as part of the job.
'88 300E (330k and soon to be put down)
'90 300CE (the new puppy)
'91 300TE 4matic
|03-04-2009, 12:17 PM||#4 (permalink)|
Date registered: Aug 2006
Vehicle: 97SL500R129, 01ML320W163, 94E320W124 & 93500EW124
Location: So. Cal.
Yes, you can "hammer" the guides out. But, its best if you buy the guide and bring the the head to a machine shop and have them press out the old and press in the new guide. Machine shops can also fit (seat) your new valves if you plan to replace them.
Last edited by edcarls; 03-04-2009 at 12:21 PM.
|03-04-2009, 01:58 PM||#5 (permalink)|
Lifetime Premium Member
The early M103s (and 1988 is early) had intake guides made of a different material than exhasut guides.
The intake guide material turned out to be too soft and wore quickly. You should have a competent machine shop press out/in guides and do a valve job. The new intake and exhaust guides are made of the same material, the harder material. So in addition to getting new guides, you get intake guides made of a better material.
The valve stem seals on your car were almost certainly replaced already since updated seals were released soon after the car was built. Viton material, I think. Make sure the new seals are the better material by buying Mercedes parts.
Have the head skimmed while it is off.
Here is a pic of the guides removed from my 88 300E when i did the head at 135k miles.
|03-04-2009, 08:07 PM||#6 (permalink)|
Thanks for all the advice. After thinking about this more, and listening to what everyone had to say, I think I'm going to bite the bullet and have a proper valve job (including new guides) done, and have the head surfaced as well. Thanks for the advice!
|03-05-2009, 07:31 AM||#7 (permalink)|
Date registered: Jul 2005
Location: Long Island
To get a ball-park figure for machine work, here is what I have experienced.
The local Mercedes dealership referred me to a machinist in the area who they use. He turned out to be great. The first head he did for me got boiled, glass beaded, had 12 new guides installed, new lifters, replaced cam, rockers and gear (good used items he had in the shop) a valve job with new seals, and skimming the head. This cost $1285.
The second head got the same cleaning process but only required new guides, a valve job, seals, and skimming. This cost $585, I subsequently replaced the lifters myself after a few of the originals collapsed on start up - (hence my recommendation to replace them)
You might want to consider replacing the head bolts as well because they are a consumable item (due to stretch). I went one step further and replaced all the exhaust studs, washers, and nuts.
|03-06-2009, 06:44 AM||#10 (permalink)|
Date registered: Feb 2008
Vehicle: 2003 Toyota 4 runner , 69 Mercury Cougar, 1989 MB 300e 245,000(Sold),1979 300d 165,000m
Location: I.E. So Cal
I had same problem almost, ,guides leaking so bad had to relace plugs about every 8K. I bit the bullet and had the head resurfaced and new guides installed for $300.00 For an extra 60 he r & r the cam and all the valves(no new parts) so I could just bolt the head back on.
Ditto on the bolts, I didn't change bolts and ended up with little gasket seaping.
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