1988TE: 6 months in, and ...

[David McConnell]

Guys,

Bought 1988 silver 300TE 6 months ago for just under a grand, 156,000 miles, auto, 7-seat, lots serv history, runs like a dream despite me doing far too many short school runs and London driving. Very happy 1st time MB owner therefore but have a few worries and hope someone can help me out? BTW I read everything on this site regularly, fantastic info and advice, so hope I'm not asking stuff already dealt with (I do do searches):

Fuel consumption: its a shocker. Don't know how to work out consumption figures but compared to previous car, Saab 9000CS, really feeling the pinch. Know 300TE cars are not designed for fuel efficiency but even so, it feels a bit much. I don't carry needless heavy loads, drive carefully(ish!), yet still too many visits to the petrol station. A service is due but is there something else I ought to do?

Temperature: if I spend more than a few minutes in static traffic the gauge moves up perilously close to 120. The fan works but even when I have a good run immediately after, the gauge does not come down, ie air-in does not seem to cool it down. Perhaps more worrying is that even when engine temp is fine, when I touch the pipes near the front of the engine bay after I've stopped they feel incredibaly hot. Is this normal? Strangely, the engine bay is miraculously clean - pipes/tubes are spotless, as if lots of the parts are new. What's that all about? Is it okay to run close to 120 and is this related to fuel consumption?

I'm on a very tight budget and my mechanical knowledge is woeful. If anyone can offer some advice I'd love to receive it. Your wise words much appreciated, many thanks in advance.

 

[Mikesmerc]

Hi David, cant help you on the fuel consumption but it is worth changing the thermostat. It may not be opening fully when correct engine temp is reached. Cheap and an easy job to do.
Regards
Mike

 

[paulcallender]

What fuel consumption are you actually achieving?

 

[Chazchuzzlewitt]

I hope it's not this but running high temps can sometimes be head gasket faliures. The 6-cyl engine is known for these. How do the oil/coolant look?
make sure your coolant is topped-up and check there's no 'mayonaise' type stuff. These cars do run hot quickly in traffic, although in my old '92 300E in 100 deg + heat in the USA the temp gauge never went over 100.

The mpg is a shocker in these cars, especially around town. I found doing 70-80 on the 'highway' at high revs much more fuel efficient than pootering around town. My economy got a bit better by running some injector cleaner, and changing some normal service items (plugs, filters cleaning some bits etc), but I swear I could see the fuel gauge go down as I was driving!

 

[sebastianforbes]

hi there david,

i have a '89 300 te.

i get 25mpg or thereabouts on the motorway - no matter how fast or slow i cruise. about 20mph in the city.

my thermostat once went up to 115 degrees C during a trafic jam this summer, but once i got moving the temp came straight back down. it worried me at the time but not anymore - it regularly goes between 75 and 90 in the blink of an eye when static.

if both the pipes from your radiator are hot then the thermostat is, at least, open. and mine are always both very hot. alledgedly, the bottom one should be cooler because it has passed through the radiator.

just monitor your coolant and that it flows.

cheers

sebastian.

 

[David McConnell]

Gentlemen,

Many thanks for taking the time to reply, much appreciated.

Mike, I hope you are right, I'll change thermostat and see what happens.

Chazchuzzlewitt, lets hope you are wrong and Mike is right! I have read on other threads that head gaskets are prone to go on 6 cylinder engines arund 150,000 miles, which is where mine is at. Oil seems fine (its light-ish brown) as does coolant, I think (unless I'm looking in wrong place, I find it difficult to tell by looking down into it). If the gasket is on its way, what sort of repair bill and issues am I looking at?

I've never heard of injecter cleaner but I'll give it a go, anything that might help mpg perfrmance would be a bonus.

Paul, as I say, don't know how to calculate mpg. I've read the threads on this subject but still not sure quite what to do! No doubt actual figures are same as others, around 15-20mpg in town, slightly higher on the rare occasions I get a run out of London. Not the best vehicle for short school runs and weekend jaunts around town I know, but then I need 7 seats for the kids and couldn't bring myself to buy an MPV, or a Volvo for that matter. Guess I should have bought a 230 or diesel but a bit late know, as don't want to part with the 300 I've got, its so lovely to drive.

Sebastian, I am reassured by your comment about how hot your pipes get too. Your point that your engine did cool down once you started moving again howevr (unlike mine) certainly suggests something needs fixing on my car. Obviously I'm hoping its the thermostat, not the gasket!

Once again, many thanks for taking the trouble to reply, and if you don't mind I'll let you know how I get on fixing the temperature/cooling problem.

 

[paulcallender]

OK here's a guide of how to calculate your mpg:

1. Fill up with fuel and take a mileometer reading (or set the trip counter to zero)
2. Next time you fill up, take a note of the mileometer reading and the fuel you put in.
3. Use the trip counter reading, or calculate the miles covered (2nd reading - 1st reading)
4. Divide the miles by the amount of fuel you put in (in step 2), in litres
5. Multpily this figure by 4.546, to convert from litres to gallons. Now you have an average mpg figure.

Some people suggest to top the fuel right up to the brim, so that its a consistent measurement for each fill-up.

 

[David McConnell]

Thanks Paul, I'll give that a go.

 

[pongee]

124 Newbie

Hi David,

Like you, I have had my '92 260E for 6 months, and am learning many things about the wonderful world of 124s. I have spent a considerable sum doing it up, and am almost happy with the result (springs, alloys & seatbelts remain to be changed).

Like you, I had problems with over-heating, which thankfully have now been resolved. Turns out I had a leaking water pump (over-engineered merc = water pump designed to leak 'behind' & not onto the serpentine fanbelt!). Are you losing water i.e. do you have to regularly top-up the water in the expansion tank?

That 115C temp you describe is definitely not normal, should be between the 80-100 range even in hot standstill traffic. A search of the forum will reveal many threads dealing with this matter, including the famous 'carrot test' to check your viscous fan. Also your high temps cannot be doing your fuel econ any good.

Speaking of which, I've just had my engine tuned, which has made a big difference to smoothness & performance. I can't yet say whether it has any bearing on fuel econ though, as it was only recently done. Thus far the average mileage I get on the beastie is around 23-24 with mixed motorway/town driving.

p.

 

[David McConnell]

Many thanks for your comments, Pongee. As far as I can tell no, don't think water is leaking - I do check water level from time to time and it seems pretty stable.

I'll search out the "carrot test" to check viscous fan, as you suggest (certainly hadn't come across that before).

If I could get 23-24 mpg I'd be happy. Its due a service and I think an engine tune would be a wise investment too. If I can sort the temperature out and get engine tuned I'm sure economy should improve, at least a little.

Once again thanks for taking time to reply and hope all continues to go well with your W124.

 

[jberks]

Hi,
can't comment on the 300TE, but my W210 240 on a school run type of journey wouldn't return more than 19-20 at best -16 ish is probably more realistic. Mine is probably built more for economy than yours - more modern and smaller, more fuel efficient engine, so what you get is probably normal.
Mercs are heavy and take a lot of fuel to get rolling. On a run it's probably not too bad as once the wheels are turning, it'll roll along without effort, but sit in traffic, with constant start/stop and the economy is awful.
I find that on a motorway, if i drop back far enough to coast to slow down rather than brake, I can add 5mpg easily.

 

[David McConnell]

jberks, I'm sure you are right, yours is a more advanced model and therefore will be more fuel efficent; mine meanwhile is older and larger and therefore inevitably less fuel efficient. That said, anything to improve performance, even marginally, would be welcome: reading another thread on super unleaded (on which I saw your comments), I think I might try Optimax: my car is pre-CAT with a large (performance) engine. I understand such an engine just might be where such fuels can make a difference...

 

[Bolide]

300TE

David


300TEs are known to be uneconomical - it's an old design and they're like a Range Rover - they don't burn the fuel, they just chuck it out of the tailpipe! However, unlike a Range Rover, they're smooth & refined so enjoy that and don't watch the fuel gauge

I've found 300s to run hotter than other W124s but it sounds as though yours may have a weak fan, a clogged-up radiator or a suspect head gasket. If it's not losing water then the headgasket is probably fine. If it's a non-aircon car it's relatively easy to remove & flush the radiator if it's blocked

If you start the engine, then slow down & hold the viscous fan, you can check the surface of the radiator as the car heats up. If it's hot in some areas and cold in others it's clogged up. Flush or replace

If the car keeps a stable temperature on the move but overheats when static it suggests insufficient air movement past the rad and this throws suspicion on the viscous fan. Replace it

If the cylinder head gasket is going you'll see oil in the water (check the expansion tank) or water in the oil (check the oil filler cap for mayonnaise). Typically a blown cylinder head gasket eventually pressurises the cooling system, blows all the water out & causes massive overheating. You can't miss it when it gets to this stage

Good luck


Nick Froome
www.w124.co.uk

 

[David McConnell]

Nick,

Many thanks indeed for your advice. I think I'm getting the point that fuel efficiency is simply not a strong point of a 300TE!

Re: temperature problem, your advice very much appreicated. I've got the car booked into an excellent very reputable garage 2nd week of Janaury. He said he'll start with the thermostat and work his way back from there. I am going to give him a print out of the advice I've received.

Its not air con, so thats good. I did mention viscous fan but he seemed doubtful, nevertheless, I'll will highlight your comments and ask him to look accordingly. If worse comes to worse and head gasket is on the way, is it worth repairing - ie whats the cost and any subsequent related issues? The car cost just under a thousand; in all other respects its great: fabulous ride, all electrics work, miniscule rust under one wing. I'd be loathe to part with it.

Thanks again,
David

 

[mjtray]

David,

I hate to say it, but if its a head gasket it may not be economical to replace it....your normally looking at £600-£1000.

Another quick check you can do, is when you start the car from cold, squeeze the top hose coming out of the radiator....if its soft and squishy head gasket should be OK.....if its already under pressure your head gasket has blown.

Good luck....fingers crossed its only a cheap thermostat.

 

[Geoff_Slade]

MB time for replacing head gasket on a 300D is 9.25 hours. So at a labour cost of £50 including VAT you're looking at almost £500 + parts (not sure how much a head gasket is but any of the Merc parts sites GSF etc should have them and will give you some idea of parts cost)

 

[pongee]

Costs

I have to agree with Mjtray & Geoff on the cost aspect of a head/gasket job. The obvious approach would be eliminate the easy/cheap items first i.e. thermostat, radiator cap, flushing of clogged radiator, correct function of viscous fan (you can do this yourself if you feel confident).

Good luck.

P.

 

[flyingtech55]

Hi chaps

On the subject of overheating problems, may I respectfully offer the following thoughts. Whenever I buy a new (used) car I do the following:

1) Renew the thermostat.
2) Remove the radiator, back flush it and blast it from the engine side with a garden hose to remove all the bits (dead insects, leaves, spiders and general muck) which clogs up the matrix.
3) Back flush the block until the water runs clean.
4) Remove and renew the 'fan belt'.
5) Grab the fan or waterpump pulley and try to waggle it while the fan belt is off. Movement often indicates the beginning of failure. Examine the area round the water pump for staining; again this can indicate leakage and replacement.
6) Renew the hoses if they are cracking or swollen though this isn't as common as it used to be.

A friend of mine once asked me to look at his 'new' car as it was overheating and he'd done all the correct stuff. 'Stat, flushing, ignition timing and so on. However he'd missed checking the front of the matrix because to was hidden away in a complex shroud. Accessing the radiator revealed that it was completely clogged with leaves' dirt, dead things etc. Cleaning out all this stuff was the cure.

If you suspect the head gasket, drop the coolant level of the header tank to give a generous air space then get a friendly (!) garage to 'sniff' the air in the header tank with their exhaust gas analyser while the engine is running. If it detects exhaust gas and gives a reading then the head gasket is suspect. Not fool proof but can give an a starter for ten.

Hope this helps,

Gliderman

 

[David McConnell]

Post subject: 1988TE: 6 months in, and ...

Thanks gliderman, pongee, geoff and mjtray for that additional advice. I only wish I was remotely mechanically competent to do some of the stuff myself. Fortunately I do have an excellent, long established family-run garage a few doors down from me who are reasonably-priced and totally reliable; they will happily take your suggestions and act on them. The car is booked in for January and I'll let you know I get on.