Technical Burning oil smell when climbing

[Hharbers]

Did road trip from Holland to Scotland and back with my 1987 panda 4x4. During trip i got more and more s tar like smell during climbs

Roadtrip op 4500km
First 1000km no problem at all
Did some very long and steep climbs like 33% hardknott Pass.
Noticed a no familiar smell during the climb. As car was close to overheating i thought it was some vapour of cooling fluid. After cooling down at top we went down without any smell

In next day we smelled it more often but only when driving up a longer (like 1/2 mile) climbs.
During road trip seemed car got more and more sensitive to climbs
At end of road trip driving home we smelled it even on the hilly parts of motorway A9 between Inverness en Edinburgh
No overheating of engine temperature
When driving (max 70 mph) on normal flat parts of roads or shorter climbs no smell at all.

Smell is like smell of tar or really Fresh laid asphalt

Back home i try to figure out what has caused this.

Coolant:
Added 1 Liter coolant halfway roadtrip after days with biggest climbs . Last 2000km no need to add coulant

Motor:
0,5l motor oil consumption in 4500km seems not excessive. No smoke from exhaust.

Rear diff:
Diff oil seal is leaking and rotation speed slings oil around so oildrops can be burnt on rear silencer. But driving up a hil the seal is highest part of rear diff so unlikely to leak more at that moment

Clutch:
Slipping clutch smells different, (i know that smell.)

Gearbox:
Could gearbox overheat during climbing and get burnt? . Halfway road trip i checked level and it was spot on.
Didnt open it yet after smell.


Any Ideas what caused this smell? As we dont have long hills in Netherlands i can not test it

 

[JAMLAX]

After recently changing my 21 year old Fiat Panda oil I have experienced the similar smell occasionally (it comes and goes) Like you I have done checks on coolant and oil levels but no obvious losses. I have heard (a YouTube Panda guy) who indicated he found an OK ring needed replacing as well as the topmost gasket - (ie NOT the cylinder head gasket). For myself, as long as normal levels of oil and coolant are maintained I'm just going to put up with the odd whiff of 'burnt oil'

 

[JAMLAX]

An 'OK' ring?
An 'O' ring!

 

[Hharbers]

Thanks
You mean gasket of valve cover?

 

[JAMLAX]

Yes.

 

[Dragon Man]

the oil cap can sometimes pass as it gets loose.. i find if you put some kind of a washer like a large thick O ring the size of the oil cap bung plug around it first, it makes the oil bung sit higher and in a position where its not loose.
i would also consider changing the O ring seal around the distributor. mine had turned into glass it was that hard.