engine and drivetrain '68 1600 Overheating

[Bdkee]

Hi fellow 02'ers,

 

I've got a '68 1600 that I recently bought and have been been working to get it back on the road. The previous owner swapped out the original 1.6l for a '75 2.0l motor back in the late nineties (done at a BMW shop in Columbia, SC). After running that for a bit the car sat and was used seldomly for about 5-10 years. Since I bought it the engine will overheat after roughly 10-15min of driving. So far I've replaced the water pump, thermostat, temp gauge sending unit, had the radiator professionally boiled, cleaned and pressure tested, flushed and burped the cooling system (lower coolant hose from the radiator does get hot), changed the oil, adjusted the timing and rebuilt the carb. Alas, it still overheats.

 

The car can sit at idle all day long and stays cool but once put under load it creeps up and ultimately pegs just at the red. Compression is good and even across the cylinders at around 115psi (cold compression). I recently checked the head and block temp with an infrared temp gauge both at idle and after the car's gauge showed it just under the red. The idle or cool temp was 160F at the head, 140F at the block. The hot (car gauge reading) temps were 185F at the head and 165F at the block. Top of the radiator temp at hot was 199F.

 

Any ideas or suggestions as to what to try next? I'm thinking a leak-down test as I'm starting to think that its going to be a head gasket (there's no white smoke blowing through the exhaust when it runs).

 

Thanks in advance.

 

Brian 

[jscaptura1]

File this under stupid things I've done! I was having the same problems with my 70 1600, changed all of the above & still the car would heat up on long drives or under load. I had not checked the transmission or rear end myself for a couple of years. I have a local school/Tech program of High School students inspect & service the car periodically and ask them to check those when servicing the car because there are small leaks in each. So I finally decide to jack the car up, put it on stands & check them myself. To my surprise (and stupidity for not doing this myself every year) the transmission was very low on oil. I added until fluid came out the side hole. Then moved to the rear end: Same thing! Filled it up & presto, car running smoother and not heating up under load. I'm not saying that is your problem but is just something else you may want to check & service. I will be doing a complete change of both when the car comes out for the spring. Also look for coolant in the oil or oil in the coolant. For me, I had no mixing of oil & coolant so I had to start looking elsewhere which led me to the drivetrain. Also check to see if any of your brakes are hanging up as they may help contribute to your engine having to work a little harder. Good luck!

[thehackmechanic]

You've done the things I would've done.

 

If, when the car is cold, you pull the cap off and start it and watch the coolant, any bubbles?

[Hans]

Its not inconceivable that the brakes are dragging, but I'd expect to see other symptoms. I assume the fan belt is tight, fresh and the pulleys are clean. Perhaps a full cooling system flush? On the gasket front, check coolant and oil for contamination and loss over time.

['76mintgrün'02]

Are those IR thermometer readings really all that hot?  

(Mine reads in the 180 degree range with the temp needle horizontal).

Could it be a gauge or sender issue?

[Mike Self]

One more thought...early US spec 02s and all (AFAIK) 1600s came with the small, four blade cooling fan.  Guess the Germans thought it never got very hot in the US.  The small fan was pretty inadequate--much smaller diameter and one less blade.  My '69 always ran hot, even when new.  Finally I discovered later cars had a larger 5 blade fan.  I fitted one of those and the temp gauge ran right at 3 o'clock.  

 

And--has the radiator ever been professionally flushed--that is, out of the car?  A 45 year old radiator can accumulate a lot of internal crud, and the radiators themselves were kinda marginal capacity-wise even when new--whay so many of us have gone to three row core radiators.  A good cleaning might do your radiator a world of good...

 

mike

[thehackmechanic]

In the original post, he said he'd had the radiator "professionally boiled, cleaned and pressure tested." Still, I've had the experience where I've done that, it didn't solve the problem, but a new radiator did solve the problem.

[jgerock]

I'd contact that shop that did the work on the radiator.  Not saying this happened, but there are/were shops that would clean the outside and paint them flat black without doing anything to the inside.

 

A local 02 owner had issues with overheating - but only when he was driving the car.  Sitting and idling would not cause issues.  5-blade fan, fan shroud and all good hoses. Thermostat was removed, inspected and checked in a pot of boiling water.   Turns out his radiator was partially clogged.  Simply installing another good used unit solved the problem.

[peterschop]

+1 on thehack's comment on a new radiator.

 

I had a similar overheating problem when I bought my car. It was fine around town but under load it would overheat. I had a new core put in my radiator and have not had a problem since. I couldn't get it to overheat now if I wanted to.

 

You may of had the radiator boiled, cleaned and pressure tested but that will not clear all the blockage out of a 40+ year radiator.

[Bdkee]

Thanks all for the ideas!

 

I haven't had any oil-coolant contamination one way or the other so hopefully its not a head / head gasket issue. To '76Mintgrun'02's point, I didn't think that 180-185F was too high a head temp either. I have had the coolant boil over before when the in-car gauge read in the red but that was prior to a new thermostat and proper burping of the system. I'll double check the trans and diff to be sure that all are topped up and then set about a new radiator and fan blade as mine did retain the old 4 fin type.

 

Thanks again. I'll keep you posted.

 

Brian

[Guest_anonymous]

double check that the temp sender unit matches the temp gauge.

what is your ignition timing set at? too far advanced may see an increase in running temp