Mayonnaise in oil filler cap - Where to start

[sujitroy]

For Stag no. 2 It not cold in California. But on short journeys I am seeing the dreaded mayonnaise in in oil filler cap.
Rebuilt heads fitted with Payen head gaskets. Oil pressure is good. (Mechanical oil gauge )No signs of it over heating on short, < 10 mile, trips. (mechanical temp gauge, show below or on N.
I have a small water leak in the Vee. The water pump was rebuilt and am not sure if the water pump is leaking too.
I have not drained the oil to see the situation yet.
If it is a head issue, how do I determine which head?
Where do I start diagnosing the problem? Car is stock with ZS carbs. I have a header tank.
Sujit

[Goldstar]

AFAIK head gaskets don’t mix oil and water on the stag when they fail. Water pump oil seal or inlet manifold gaskets I reckon

on second thoughts I don’t think an IM gasket failure
would mix oil and water either so I’m going water pump seal.

[richardthestag]

quickly get some bread and make a sandwich

Lots of short trips can easily cause this, especially at inclement months of the year. condensation builds up inside the engine and never gets chance to boil off.

I always thought it was rare for oil and water to mix on a stag v8 because of HGF. more likely for the cooling system to over pressurise because of combustion gases. Is it doing that?

Why drain the oil when you can just pull the dipstick

[sujitroy]

There was no noticeable water on dip stick. But since it had new heads on it, its due for an oil change, My auto in the 20 years driven about the same never showed signs of mayo, as mentioned its warm here in California about 60 F. Pressure seems normal. I've heard the water pump seal can fail, but I triple checked that on installation, but will check the water pump again. It's a manual and I'm thrashing it a little bit. Seems to have brought my youth back. Haven't driven a manual is years. No need for that blue pill. Would that make a difference, Good to know it' unlikely to be a head gasket. I just too a look at my spare engine and the oil path, back of block, from the block to the head is quite a distance away from the nearest water passage,
I'll report back. Thanks.
Sujit

[RobinLegin]

Just a thought Sujit, but how many miles has the car done since the engine was reinstalled? My local Stag specialist wanted the car back after 600 miles and then 1,000 miles to retorque the heads after he rebuilt the engine. And I have since had to sort evidence of water in the V, though this was clean. Now resolved hopefully.

Another though, but were the heads initially torqued down to the correct PSI and in the correct order for each bolt? In my misspent youth I had a mini which I failed to torque down properly and shortly afterwards the mayonnaise was visible in the oil filler cap. It required a further oil change and retorquing again.

[sujitroy]

Just a thought Sujit, but how many miles has the car done since the engine was reinstalled? My local Stag specialist wanted the car back after 600 miles and then 1,000 miles to retorque the heads after he rebuilt the engine. And I have since had to sort evidence of water in the V, though this was clean. Now resolved hopefully.

Another though, but were the heads initially torqued down to the correct PSI and in the correct order for each bolt? In my misspent youth I had a mini which I failed to torque down properly and shortly afterwards the mayonnaise was visible in the oil filler cap. It required a further oil change and retorquing again.

Hello, Robin, I haven't driven the car much, maybe a a hundred miles or so but not much more, but I have torqued down the heads in the correct order initially to 55 then I read somewhere this forum that they should be torques down to 65 which they are now.
Sujit

[DZP]

Hi Sujit,
It might be worth checking that the engine breathing system isn't blocked.
Check the cam cover filter isn't blocked and look for collapsed breather hoses.
Den

[sujitroy]

Hello Den, I have a Fed. '71 it has some basic emissions stuff on it. That appears to be fine. I do have a major manifold leak. now, but will need to determine if the water pump is leaking too and see if that resolves the problem.

Sujit

[sujitroy]

Just an update from April. I removed the inlet manifold and sealed with Tiger seal. Taken the car for a few short runs and no mayonnaise which is good news.
Sujit

[jbuckl]

Good to hear