Questions on 300D engine rebuild
 

I have a 1977 300D with true mileage unknown. I took it recently to have the valves adjusted and compression checked. It came out with a compression of 340 to 350 on three cylinders and only 230 and 240 on #3 and #5. The piston rods are not warped, however the mechanic recommended to rebuild the engine - cost $6300. Could I get by just by changing the valve seals without going through all the rebuild process at this time?

Thanks for the advice.

Cris

rebuild
 

Adsit offers rebuilt engines for 3995+400 core. I'm sure there are used engines out there much cheaper. Sounds steep. Did the mechanic do a wet compression test, also? That would give you an idea where the problem lies, ie head or internal block.

The valve seals have nothing to do with the compression reading.... they only affect the gases which make it past the valves where they contact the surface of the head at the combustion chamber...
Your next move should be to have a leak down test performed ( by a different place ) ... during which they should introduce some oil to each cylinder to try to determine what is causing the low compression... while it can be both the rings and the valves... it is more commonly one or the other... thus if you find it is more the valves ( little effect on the leakage effected by the addition of the oil in the test ) then you might get by with just a valve job... a much cheaper situation than what he is quoting....
No matter what... the quotes he has given are higher than you can find elsewhere.. another reason to get a second opinion from someone .... and I would not rule out taking it to someplace like ' LemonBusters" where about $100 should provide the compression or leak down test you need... and a disinterested opinion...

Yes indeed there is a problem in that hole, but 240 is not really critically bad. If the engine is not sucking too much oil, starting and running okay, I would just drive it awhile.

BTW, when doing a leak down test there is no need to squirt oil in the cylinders. You simply listen for the source of the leakage. If you hear hissing from tailpipe, it is an exhaust valve. If you hear it through the air cleaner it is an intake valve. If you hear it through the oil cap, it is rings or cylinder related.

Good luck,

If you hear it thru the radiator, head gasket and/or cracked head/block.(been down that road with a gas engine)

Welcome back Larry,


If one constructs their leakdown tester properly it is NO Trouble to inject the oil... just turn a couple of valves....

If you rely on listening then you have to hope the noise gets through the head, turbocharger,feet of exhaust pipe, one or more mufflers and that your hearing is still good enough to hear it...

I'd suspect the valves before the rings on a 617. Adjust the valves and leave them a bit loose (larger clearance) and re-check in 1000 miles. If the engine hasn't been maintained very well, oil leaking down the intake valve stem can coke on the stem, holding the valve open. With the extra clearance, the carbon will rapidly wear off and allow the valve to close.

Check the valve stems for excess clearance while replacing valve stem seals if you do that -- any palpable side movement means its valve job time on a car with unknown milage and maintenance.

Peter

So is the 617 NON TURBO just like the 616 except for one more cylinder. I mean its only the turbos that have all the extra beefing up and oiling system for each piston, which I assume is what makes the turbos engines so much more expinsave to O/H per cylinder compaired to the 240 engine? and the 617 NON TURBO? :confused: Thanks

I would say ' yes' to that question..

check out metric motors they have A web site there in the LA area all they do is rebuild benz motors you might be able to get A completly rebuilt one cheaper than you were quoted and it comes with A warranty,they supply for performance products

Whoa Jeremy.... we are a frugal bunch here and are a long way from suggesting he get another engine (yet)..... :D
In fact...we are fully hoping to get him fixed up for less than the cost of SHIPPING an engine from LA to Corpus..... :D

Did the engine have a problem or was it just in the shop for a regular sevice? If it's running OK, why spend money trying to fix it.

Exactly! Why mess with something that isn't broken. Keep driving it as long as it runs. For the price of another engine you can buy another car.

Thanks for all the info. The only problem I have with the car is the fact that it is hard to start. I usually have to give it some starter fluid as an aperitiff to coax it. Once it gets going it runs great. As far as rebuilding the engine, not just yet. After all I paid only $400.00 for the car. I also need to change the shocks, the servo unit for the heater/AC and the auxilliary water pump. For now it is a nice replacement for my V70XC that I will keep as a family car.

PS. Where can I get a cheap servo for this car - my dealer qoted me $400.00?

If it runs great, forget the rebuild. If the only problem is hard starting, it could be just a minor issue. Do a search on this board on starting. There are many things that can cause this.