Beetle engine over heating

[advinnie]

Hi all got have a 1971 1200 bug running a 1600 engine with a pair of ICT carbs and she over heats when ever I go over 45 mph. At 45 mph she will run at constant 105°c on my gauge but increase the speed to 50 mph the temperature will slowly go up to 130°c and my save my bug dipstick probe sets off the oil light. Of cause the faster I go the quicker the oil temperature increases. Now once the save my bug sets of the oil light and I pull over and allow the engine to tick over at idle the temperature falls back to 94°c in ten minutes.
all the tinwear and rubber seals are in place, I’ve tried setting the timing at 28 to 32 BTDC but that’s made no difference at all. I’m using a SVDA distributor.
I also have 10psi oil pressure per 1000 rpm even at 130°c but I’m using 20w50 oil witch came with the car. Also I have a solid engine lid and the larger fan with the dog house fan shroud, I have two other friends using a solid deck lid as well on there 1600 bugs and they have no problems at all.

any ideas on what the problem could possibly be?
Thanks for any advice that you lot have

[V8Nate]

The thick oil could be your issue not allowing your oil pressure relief valve to let oil properly go thru your oil cooler. I'd suggest try putting some 10w30 in it and see if that helps your temps.

Another issue is it could be lean or improperly set linkage. Both carbs need to open the same amount at all times and adjustment is crucial on a dual carb setup.

On ict's, I've had Italian weber ict's and empi ict's, both were very lean out of the box especially on cruise(I have a wideband o2 and it would peg the gauge completely lean, it also ran like crap on light throttle) and when the fuel switched over to this ethanol crap I had to go up 1 size in jet and lower the fuel level in the bowls slightly(the ethanol mix has a lower boiling point so gas would percolate out the vents)

I would start with the oil(wouldn't hurt to check the valves while your at it) and make sure both carbs linkage are setup properly and mess with jetting after those are checked off the list

[Bruce.m]

Also worth checking the oil pressure relief valve piston moves in the bore & is not stuck open.

Is the oil cooler hot and blowing hot air out of the exit next the gearbox?

Does sound like the oil is not going through the cooler or there is no airflow across it, for some reason.

[advinnie]

Ok I will try 10w30 mineral oil and see what happens.
I’m running 57 idle jets and 140 mains in my Weber 34 ICT carbs.
The oil pressure relief valve is moving up and down I’ve checked that one but I’ve not checked the other one at tbe flywheel end (don’t know what that one is called)

I will check tomorrow and see if the oil cooler is hot and if any air is flowing through it

[Bruce.m]

If the flywheel valve is jammed shut you’ll get excess pressure & if it’s stuck open you get low pressure.

[advinnie]

That valve must be working ok cause on a cold start up I have 80psi of oil pressure at idle and it doesn’t get any high than that if I increase the rpm around 10ish when nice and hot

[advinnie]

I’ve been looking at the beetles oil systems which is something I’ve never done before I just put oil in and off we go and if I’m right here the oil system is not temperature operated but pressure operated?
So the oil system doesn’t care what the temperature is it just wants the pressure correct, if I’m right on this it means that if you put a thicker oil in the oil temperature will be higher than that of a thinner oil to get to the correct pressure?
I’m on on your something here or have I got this all wrong?

[Slow 1200]

yes you are correct, but still even with 20w50 and a non-vented lid your temperatures seem extremely high, how are you setting the timing advance? with a SVDA you want to set the maximum on the centrifugal only with the vacuum disconnected

[advinnie]

Yes I have a SVDA Unit and set it with the vacuum pipe off using a strobe gun but the timing is flickering all over the place it’s not steady at all but it never goes above 32 BTDC

[Bruce.m]

The oil cooler “thermostat” works by opening the bypass valve (skipping the cooler) if the oil pressure ahead of the cooler gets too high. With all other factors being to original spec, this happens with cold oil as it takes too much effort to squeeze though the cooler. Saves the oil cooler bursting and gets the oil up to temp faster.

[advinnie]

Thanks for that mate

[Phil69]

I might be tempted to go up one size on the main jets (145's).
Too lean a mixture and too much advance is a common cause for an old aircooled to run hot.
I say this as I used to have the same issues with a single carb 1600. The problem in my case was a partially blocked main jet and emulsion tube.

[JeansMod]

Would be curious Advinnie if you ultimately have sorted out the overheating problem and which was the cause. I see a lot of time has elapsed since this form was opened

[advinnie]

Would be curious Advinnie if you ultimately have sorted out the overheating problem and which was the cause. I see a lot of time has elapsed since this form was opened

Sorry for the mega late reply mate.
I've not yet driven the bug since posting this thread.
I will tell you what I've done.
I've now go for a straight 30 weight oil and binned the 15W50 oil I was running, set the timing to 28⁰ BTDC instead of the 32⁰ I was running, reset the valve clearance from 0.004" to 0.006", just finished fitted a vented deck lid and a new fan shroud because the old one in the end only had the cooling flaps over cylinder 3 and 4. I also found out that the oil cooler was leaking from the seals on the engine case so have now sorted that out. I am hoping as a matter of fact to have a test drive this coming weekend, if I do I will report back to you on hiw it went.

[advinnie]

At last I’ve had a chance to take the bug out for a drive and it’s working. Went from a 50weight oil to a 30 and that helped but what done the job was fitting a four slotted deck lid. Went for an hour drive of mixed speeds, at 70 mph the oil temperature hit 107°C dropped down to 60 mph and it dropped to 105°C, around then it sat at 95°C. When I got home I allowed the car to idle for a while and noticed the oil temperature dropped to 85°C is this normal?