On the way to the Milkshake run my cab started to overheat. Not very nice noises etc. Anyway this engine I rebuilt last year and all looked good but after this episode I have pulled it apart again but everything looks good (in regards to causes not effects). The thermostat that I still use is in good condition and works, the flaps work, the oil cooler is not blocked, the relief valve and control valve both work although the relief valve did appear a bit stuck when I tried to remove it but no more than a bit of oil pressure wouldn't have been needed to move it. Nothing wrong with the oil pump. I can see maybe an oil gallery could be blocked somewhere I haven't got that far yet. The way the oil was smoking from the filler tells me this was an oil problem not an ignition problem as I first thought as the spark plugs are all good and the valves and heads are good as well so does anyone have an idea before I rebuild this? I'm looking for as many suggestions as possible here so please don't be afraid with as silly a suggestion as you may think of. Steady Matt!!!!

Hopefully just over heating...

if the oil pressure piston sticks then no oil goes thru the oil cooler
and that would over heat an engine...

as the engine thinks that the oil is still thick and cold..??

all tinware and rubber seals in place?
heater hoses in place?

LEE

I've had similar problems with late engine in early body, not being able to pull enough fresh air. Solved with hole saw and slightly raised number plate.

What engine and body combination do you have?

Mine is 1300 twinport (effectively 1600 tp, = larger fan + dog house cooling) in a 1961 body. The bigger fan trys to pull more air than the body's air vents can physically supply.

There are other solutions, such as hoodjax ect.

Regards,

Matt.

yES,
the 1500 beetle without any engine lid vents does overheat in the summer at 100kmh speeds

hoodjacks etc really make a difference there...

but if you have a larger engine in an early body You do need to modify the engine lid etc...

unless You are driving in Scone at the moment.. 9c
and around -1c over night... morning..

LEE

'79 cab only has the vents in the engine lid and it's the original 1600 FI engine. I would've thought the relief valve and control valve would have compressed when cold as the oil would be thick therefore higher pressure and when hot the opposite so if they were stuck at the top of their reach it would always send oil via the cooler and be safety feature. Please correct me if I'm wrong.

YES

when the oil is cold and thick, and the oil pressure is very high, the plunger/piston is in its lowest position and oil flows directly to the engine lubrication points and back to the sump..

when the oil warms up and thins out, the oil pressure drops, the plunger/piston covers the bypass port and oil flows to the lubrication points both directly and via the oil cooler..

when the oil has reached its normal temperature, oil is thin and oil pressure is low, the plunger/piston is in its highest position... and all the oil goes thru the oil cooler after going thru the engine...

from chilton's 1971 manual..

cheers

LEE


try hood jacks etc....

Prop the decklid open with a tennis ball jammend in the catch then drive it and see if you can get it to get close to overheating.

If it stays cool then it's an airflow problem

If it gets close to overheating again then it must be an oilflow problem


Regards,

Matt.

send it to a meknic?

I seriously doubt it's an airflow problem as it's completely factory and hasn't overheated in the last 30 years No it seems I'm just going to have to bite the bullet and put it together and triple check everything..........again.

My Dad often tells a story of brand new bug he passed one weekend back in 1961 going up Bells Line of Road near Sydney. If you don't know it it's a bloody steep hill, and this bug had a huge plume of smoke coming from the back of it.

Sure enough, he saw the car in the shop at Lannock Motors on the Monday... first week of ownership and cooked engine due to stuck a oil pressure relief valve.

You will all have Us checking Our relief valves Dave... lol

LEE

Well no new suggestions, I'll just have to clean everything and rebuild it but now I'm puzzled as the only thing I found wrong was the oil pressure control valve stuck(not the relief valve as I mentioned earlier). I would have thought this would keep oil going to the cooler and so not letting it overheat ?! Maybe it might be time to start getting on the wifes' good side as a new engine may be needed down the track if after this it decides to play up again

Then you need to get that manx on the sand after you do the cab.

Don't worry Shane that's on the 'To do' list, just have to weld the floorpan then put it all back together but the convertible is the priority.