[PUSB]

Hi,

My MGF has been losing coolant for a few months now, and the dipstick often has (a considerable amount of) the dreaded Mayo on it.

However, a good long drive clears the Mayo and at a recent change the Oil was blacker than a bailiffs heart.

Does that mean its likely the coolant isn't leaking into the oil?
A quick google of coolant in oil shows the oil turning a sort of beige colour, whereas what came out of mine was thick and black.

It had a head gasket change 18 months ago so I'm desperate for it not to be that again!

 

[MidgeVVC]

A little " Mayo" on the dipstick at this time of year is not unusual due to atmospheric condensation and little running time Have you got "Mayo" at the filler caps?
If you have apparent coolant loss, first bleed all 3 bleed points and check your jiggle valve.
Please don't jump to HGF and keep the faith.

 

[Man in the Car]

There is a general opinion that emulsion can form to some extent as a result of condensation forming in the engine in cold weather and only doing short runs which will not get it hot enough for long enough to evaporate the moisture for it to be drawn through the cam cover breather into the induction system.

However, I have become a little sceptical of this since replacing the head gasket on my ZR in 2013 - it always used to have either a few droplets of moisture or a suspicion of emulsion in the oil filler cap, but since the HG change it has lost no coolant whatsoever, and the inside of the oil filler is always dry as a bone, even when it has been freezing weather.

The only other way moisture can really get into the oil in enough quantity to cause emulsion to form is either HGF or a crack in the engine casting. If there is enough moisture to cause emulsion to form on the dipstick as well as in the filler cap, I would tend to suspect the head gasket tbh. As you are also using coolant, this would increase my suspicion. As a guide, my ZR had been using a little coolant and there had been emulsion forming both in the expansion tank and in the oil filler cap (none on the dipstick though), but the oil that I drained out showed no sign of having coolant mixed with it (like yours). To make the sump oil turn emulsified, you would need a quantity of coolant that would drain the expansion tank to the point that it would be very obvious that something was amiss.

To start with, you need to have a very careful check around all the coolant pipework, rad, inlet manifold ends and coolant cap to see if you can find any trace of either a leak or signs of lime deposits where coolant may have been leaking and evaporating. Always worth changing the expansion tank cap for a new (genuine) one too, as a failed seal will give rise to similar coolant loss.

 

[mhack]

you havent said how much coolant you are using? and stable temp gauge?

 

[PUSB]

you havent said how much coolant you are using? and stable temp gauge?

Temp is stable (I'm assuming its because I keep topping it up.

Two trips will cause the coolant level to drop from the max line to minimum. Strangely its not related to distance. If I drive 5 miles, or 100 miles it will generally drop by the same amount.

Also forgot to say that the coolant is clean.

 

[mowog73]

It doesn't sound like HG failure to me, at least that wouldn't be my first guess, it sounds like you have coolant weeping from a hose/pipe connections once the coolant system gets pressurised or maybe a faulty expansion tank cap.

I'd suggest adding coolant dye to the reservoir, run the engine and then search for a coolant leak using a black light. My F had a multitude of leaks when I bought it and I was able to track down and fix each one with the help of the fluorescent marks left behind by the coolant dye.

If you don't recall the last time the expansion tank cap, I'd also suggest replacing the coolant cap.

 

[JoCoLo]

I worried far too much about this when I got my F 5 years ago. It was due to short runs, take it for a good blast of 20-30 miles and it all goes. I guess the heat will evaporate the water that has accumulated. This HGF thing can play on our minds. Mind you I must admit when I bought the car I used they mayo to get a few quid knocked off the price.

 

[coffeebreakbios]

My TF has shown slight signs of Mayo on the dipstick on and off for over 2 years now.
I did leak down tests, CO2 gas leak tests, water pressure tests all to no avail. everything checks out ok.
She never uses water or oil or overheats, exhaust fumes are clean and she has plenty of power.
I've resigned myself to completely ignore it, if and when she blows something, then I'll think about fixing it

 

[mhack]

next question, the pressure in the header tank the follow day once the engine is cold, is there any pressure when you undo the cap? you might be overpressuring which will probably be HGF.

also, mayo on the underside of the rocker cover? check that area.

 

[coffeebreakbios]

next question, the pressure in the header tank the follow day once the engine is cold, is there any pressure when you undo the cap? you might be overpressuring which will probably be HGF.

also, mayo on the underside of the rocker cover? check that area.

No pressore when cold, and no excessive pressure when hot, temp guage sits on normal. exhaust clear and the car drives well
Theres no mayo on or around the filler cap, or water pressure cap, it occasionally shows up only on the dipstick.
I'm going to do a filter and oil change, plus remove the sump over the weekend.(I've got a slight oil leak from sump gasket)
Maybe it will show something up when the sumps off.
I'll let you know what's found if anything.
Cheers Ray

 

[coffeebreakbios]

No pressore when cold, and no excessive pressure when hot, temp guage sits on normal. exhaust clear and the car drives well
Theres no mayo on or around the filler cap, or water pressure cap, it occasionally shows up only on the dipstick.
I'm going to do a filter and oil change, plus remove the sump over the weekend.(I've got a slight oil leak from sump gasket)
Maybe it will show something up when the sumps off.
I'll let you know what's found if anything.
Cheers Ray

I've fixed the small leak in the sump gasket, yes there is a tiny amount of Mayo, mainly inside the dipstick tube. it was obviously breathing it through the tube.
I cleaned it all the pan out.

I then took off the rocker covers so that I could check it for mayo plus to flush the old oil out of the system.

I found a circle of thick mayo around one of the head bolts.
I checked the tightness of the bolt with a torque wrench and it was fairly loose, a further check found 2 other bolts loose.
After taking one of the bolts out I've found it was streched.

I have a full gasket set in my garage, so I changed the head bolts in sequence one by one and torqued them down.
Hopefully, with the leak being so minute the gasket will fully reseal itself.
I'll give it a good road test then keep an eye on it.
If the Mayo comes back, then it will be the dreaded HG change and a skim.

 

[D4KGP]

I've fixed the small leak in the sump gasket, yes there is a tiny amount of Mayo, mainly inside the dipstick tube. it was obviously breathing it through the tube.
I cleaned it all the pan out.

I then took off the rocker covers so that I could check it for mayo plus to flush the old oil out of the system.

I found a circle of thick mayo around one of the head bolts.
I checked the tightness of the bolt with a torque wrench and it was fairly loose, a further check found 2 other bolts loose.
After taking one of the bolts out I've found it was streched.

I have a full gasket set in my garage, so I changed the head bolts in sequence one by one and torqued them down.
Hopefully, with the leak being so minute the gasket will fully reseal itself.
I'll give it a good road test then keep an eye on it.
If the Mayo comes back, then it will be the dreaded HG change and a skim.

I think that having a full gasket set and replacing the head bolts you might as well have gone ahead and done a gasket change. Regards. D4KGP.

 

[coffeebreakbios]

I think that having a full gasket set and replacing the head bolts you might as well have gone ahead and done a gasket change. Regards. D4KGP.

At the moment I don't have space to do major repairs due to parking on my driveway, my garage is full of boxes as I have just moved in, then the garage has to be fitted out, given time it'll be done.
Ray

 

[JoCoLo]

My F hasn’t been on a long run for a year, just local 5 min trips, there is mayo all over the dipstick.

 

[D4KGP]

My F hasn’t been on a long run for a year, just local 5 min trips, there is mayo all over the dipstick.

I think that I would be more inclined to investigate the mayo situation rather than moisturising the leather seats. Regards D4KGP.

 

[coffeebreakbios]

I think that I would be more inclined to investigate the mayo situation rather than moisturising the leather seats. Regards D4KGP.

I'm not too worried about the mayo as long as I change the oil regulrly., If I give the car a good 20min run, the mayo's gone.
The slight hg leak was definitely seeping up from a loose head bolt, a coolant high pressure test has confirmed this.
There were no leaks detected from a blow down piston test, or CO2 leaks in the water, so the pistons seal fine.
The car was (supposed) to have had a new head gasket water pump etc a couple of months before I bought the car.

We have planned for the engine to come out anyway,, give the old girl a subframe de-rust, clutch, gaskets, valve seals etc.
weather and the refitting of the garage at my new home has delayed our fun.

 

[JoCoLo]

I think that I would be more inclined to investigate the mayo situation rather than moisturising the leather seats. Regards D4KGP.

One run more than 20 miles and it’s gone. It’s just from moisture in the dipstick tube.

 

[coffeebreakbios]

One run more than 20 miles and it’s gone. It’s just from moisture in the dipstick tube.

Yip I'll definitely do that, I'm not 100% sure about the mayo I found round the head bolt, but 2 new bolts have been inserted and all of the remaining bolt torque settings have been checked, found 1 very loose and 2 bolts a bit below torque.
It might just have been giving a tiny weep into the oil causing the tiny bit of mayo.
Cheers Ray

 

[Man in the Car]

....all of the remaining bolt torque settings have been checked, found 1 very loose and 2 bolts a bit below torque......

Interested to know how you assessed that two were "a bit below torque" as there is no actual torque setting for the tightened bolt? The K series bolts are tightened to a settling torque of 20Nm and then angle tightened through one full turn in two stages of 180 degrees (or 180 + 135 if using the SAIC gasket and 10.9 bolts).

If one was loose and perhaps others not fully tight, it does indeed indicate that either they were not correctly tightened to start with, or they were already stretched too far beyond yield - once got to this point, they will just continue to stretch further and will still impose insufficient load, so it is good that you have replaced them.

 

[coffeebreakbios]

Interested to know how you assessed that two were "a bit below torque" as there is no actual torque setting for the tightened bolt? The K series bolts are tightened to a settling torque of 20Nm and then angle tightened through one full turn in two stages of 180 degrees (or 180 + 135 if using the SAIC gasket and 10.9 bolts).

If one was loose and perhaps others not fully tight, it does indeed indicate that either they were not correctly tightened to start with, or they were already stretched too far beyond yield - once got to this point, they will just continue to stretch further and will still impose insufficient load, so it is good that you have replaced them.

I've got a torque guage, set it for an anti clockwise bolt and read the setting on the guage, I set it to beep (torque) at 20nm.
The loose bolts did not reach 20nm before they loosened, hence they were loose.if they reached 20nm (beeped) without moving, I left them alone,
I know the bolts are torqued higher than 20nm because of the angle tighten, so it's safe to test the bolts this way.
Not fully accurate, but it works to test for loose or stretched bolts
The last owner stated that the car had a new gasket fitted, it's possible they did not tighten them fully.
The bolt I fully took out (the one with the mayo around it) was definitely stretched, this was the loosest one.