The cold verses 107 engine - help on some noted concerns

[IrishRJ]

The weather has been cold, no very cold and its been harsh on our old R107’s. Mine is at 1972 350SL. I try to drive mine twice a week to keep things ticking over. But as of late I have noticed difficulty when pulling away after starting but after a few minutes of careful driving revving and the engine warming up the car runs smoothly

I’ve also noticed small knocking noise, think it might be the tappits can these wait till next service or is it something that needs urgent attention. Or it might be that I am using the wrong octane fuel (normally 95 RON). I have heard of other early 1970's 350SL fuelled by higher octane fuel like Super unleaded - 98 RON, I use Ordinary unleaded - 95 RON. I know the old 4 Star leaded had 98 RON. Is this the fuel I should be using as I don’t use lead additive and my car is 1972 manufacture. If I continue will I damage my engine and if I change will I need a re-tune. Wish I knew more about car mechanics.

Another item I have notices which has got me scratching my head is slight mayonnaise on the oil at the end of the dipstick, I know that mayonnaise under the oil filler cap can be a sign of early head gasket failure but it’s only appearing on the end of the dip stick. Racking my brain as to how water is getting in at the end of the sump. Also the oil levels are not dropping appears to be at the full level and slightly above over the past 200miles. More potential worry for my dear R107


All help is much appreciated, and thanks for departing you knowledge on the above items

 

[grober]

Sorry sounds as if it might be the start of a head gasket failure. Get a garage to check for exhaust gases from the coolant filler cap- quite a sensitive test done correctly. Pinking or engine knocking due to lower octane fuel usually sounds more like a high pitched ringing sound like a little bell without the reverb . Your age of engine might well require a lead substitute additive to the fuel to preserve the valve seats no matter what octane fuel you are using.

 

[IrishRJ]

Thanks for advice Graeme, hoping it wasn't head gasket as that sounds expensive and there is no mayonnasing under the filler cap yet! How much is head gasket repair. Will ask the garage to check at next service towards end of Feb. If I add a lead substitute will I need a complete re-tuning of the engine?

 

[74merc]

How long do you drive the car for when you do start it? I'm only guessing but I'd say that a combination of short drives and the cold weather would not be sufficient to evaporate any condensation built up inside the engine, hence the mayo in the oil.

 

[IrishRJ]

I try to drive it twice a week, short run during the week for 30-40 mins but because I live in London this doesnt allow me time to get it up to speed. On weekend take it down the A3 hitting average 70mph for 30mins or so which should get the condensation build up out. I need to check the coolant level because it has early symptoms, or merely suspect a HGF, chemical test of the coolant is proabably best way forward but due to Christmas cannot afford to do it now. Lets hope its condensation 74Merc

 

[IrishRJ]

Just quick note: has anyone used K-Seal applied to cooling system and will mix with most anti freeze and claims to seal a head gasket and other cooling leaks??

 

[kwakdonut]

I would imagine that, at very best, something like K-Seal would only be a temporary fix. Your car is a classic and should surely be kept running regardless of cost?!!

 

[IrishRJ]

Thanks Kwakdonut, I have kept it in tip top condition with gearbox and brake overhauls etc coming to value of a good second hand R107, HGF can be another £1000 on top and would like to play the preventive card with good maintenance rather than wait and fix it card as works as we all know on MB are costly.

 

[kwakdonut]

£1000!!!!! Cripes - see what you mean.

Obviously it is an old car but that doesn't always necessarily mean big bills and bad things to come!!! 'Mayonnaising' at this time of year is not uncommon in even new-ish vehicles. As has been said, takes quite a while to get rid of condensation within an engine if it's not used for long runs etc.

Anyway, hope it will be ok - am sure it will!

 

[lynall]

Bloke at work has an v6 Omega and i was looking under his bonnet the other day as you do! and he was telling me every winter his filler cap has mayo on, come the summer its gone again and has been the same for the last 5 years and doesnt use any coolant.

I would hazard a guess and say dont worry, just watch the levels and change the oil more often.



Lynall

 

[IrishRJ]

Kwakdonut thats what I thought, lets hope its only condensation but will go and get it coolant emission tested for about £50, good time to get the tappits adjusted as well. thanks

 

[grober]

Thanks for advice Graeme, hoping it wasn't head gasket as that sounds expensive and there is no mayonnasing under the filler cap yet! How much is head gasket repair. Will ask the garage to check at next service towards end of Feb. If I add a lead substitute will I need a complete re-tuning of the engine?

Don't think any retuning will be required if you use a lead substitute additive but no doubt the additive manufacturer will advise on the container/packaging..
Using an coolant additive is not a good idea since it just clogs up the narrower water passages.
A head gasket repair is quite expensive due to the need to remove all the ancilliaries inlet manifold and drain fluids etc. If you are doing one bank you should seriously consider doing the other side and depending on the condition of the valve timing gear/chain even consider a full top end overhall. Sounds a bit daunting but while the top end is in bits anyway-----------???
First thing is to be sure the head gasket is gone-it could just be condensation as has been said but coupled to the slight hesitancy when starting from cold= possibly a little water in the combustion chamber? it has to be checked out. If you can remove the spark plugs easily enough take them out and have a look at the electrodes- should be a nice brown colour maybe a bit black running from cold-if however 1or 2 look different from the others "oily" i.e. moist black then that could be water in the combustion chamber. The other thing to check is any black scum in the coolant overflow tank- the coolant should be a "clear" yellow or blue or green dependant on the antifreeze used.

 

[IrishRJ]

Graeme thanks again will take a look and monitor, will wait for next service in spring to carry out test. But will keep close eye on it until then.