Headgasket or thermostat

[davidpidge]

I had a suspected headgasket failure (mayonnaise in oil cap/brown sludge in radiator) but after being advised to check the thermostat incase it's seized shut it seems that it could be the issue.

Got this off. No issues.

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The thermostat looks mint.

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I want to drain the head and flush it through because clearly it's a mess. I can't see a drain tap anywhere. Certainly nothing like the drain traps shown on technical drawings. Any photos of what to open up to flush her through?

I have a new thermostat and housing ready to go. Then I'll test that before going ahead with a new headgasket.

[svenedin]

Later cars have a plug fitted instead of a tap. It's on the right had side of the engine at the back as seen from the front of the car.

When you remove the plug it is very likely that no water will come out as it will probably be absolutely blocked with sludge. Search the forum for tips on how to free this. I managed to get it to go by laboriously poking with a screwdriver and then coat hanger wire.

Flush everything including the radiator (remove bottom hose) with a garden hosepipe until the water clears. This can take absolutely ages. Then fill the system back up and run the car with a proprietary cooling system flush (e.g Holts Radflush) and drain again after the car has been run up to temperature and driven around a bit. With that degree of sludge you will probably have to repeat this. When it is eventually clean make sure you use antifreeze which not only inhibits freezing but corrosion too. Tip: you can connect a garden hose to the heater outlet on the block but make sure the valve is open of course. Also a good opportunity to force water up one of the heater hoses and it will flush out of the other pipe. Bound to be loads of muck in the heater matrix too.

Mayonnaise in the rocker cover is often a sign of a blocked or ineffective breathing system (or sometimes the wrong type of oil filler cap too). Check this too. If in doubt just ask.

I will take a photo for you now.

Stephen

[svenedin]

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[davidpidge]

Excellent thank you! I was going to undo that so thanks for confirming. So I'll remove that, blast some water down the thermostat hole and see what happens.

[ManyMinors]

In my experience, "mayonnaise" inside the rocker cover is more a sign of short journeys and the engine not reaching a good running temperature than a sign of head gasket failure. This is particularly true during the colder months - and the Minor engine tends to be over cooled, having a rather large radiator. Unless you are loosing coolant or looking for a job I wouldn't rush to remove the cylinder head.

[geoberni]

Excellent thank you! I was going to undo that so thanks for confirming. So I'll remove that, blast some water down the thermostat hole and see what happens.

If you find that tap waterway clear, it'll be the first I've heard of.
Take a read of this topic. It's got all the background info you need.
viewtopic.php?p=606323#p606323
I cleared mine out in 2017 and despite miniscule mileage over recent years, it was blocked again recently

There seems to be little pattern as to whether an engine has a Drain Tap or not. The Parts List references the Drain Tap 'Service Use only' so make of that what you will.

[svenedin]

In my experience, "mayonnaise" inside the rocker cover is more a sign of short journeys and the engine not reaching a good running temperature than a sign of head gasket failure. This is particularly true during the colder months - and the Minor engine tends to be over cooled, having a rather large radiator. Unless you are loosing coolant or looking for a job I wouldn't rush to remove the cylinder head.

Yes because it’s a water/oil emulsion and if the engine never gets properly hot the water vapour condenses at the top of the engine and get whipped into mayonnaise with the oil by the rockers then flung onto the inside of the rocker cover. It’s definitely made worse though by ineffective engine breathing. I cured my mayonnaise problem by unblocking my tappet chest breather.

[davidpidge]

The drain hole is solid with sludge. I can get a screwdriver in about an inch. The small hole that goes down from under the thermostat is also solid. Going to try pouring some citric acid in and letting it sit over night. This could take a while.

The mayonaise has been getting progressively worse and the engine is running hot which is why I assumed a headgasket failure but I will persist with getting the water coolant running through the head and block then see where we go from there.

[svenedin]

The drain hole is solid with sludge. I can get a screwdriver in about an inch. The small hole that goes down from under the thermostat is also solid. Going to try pouring some citric acid in and letting it sit over night. This could take a while.

How did it get quite so bad? No wonder the engine is running hot.

It will take a while. Citric acid works much faster when the solution is hot. Trouble is even if you start with a very hot solution it won't stay that way for long with that lump of cast iron.

[Sleeper]

Just thinking out loud , could you run the engine with citric acid as coolant, will circulate it and bring it up to temperature...maybe the only downside is that the radiator fins might not like it ?

John ;-)

[davidpidge]

Just thinking out loud , could you run the engine with citric acid as coolant, will circulate it and bring it up to temperature...maybe the only downside is that the radiator fins might not like it ?

John ;-)

From what I've read in older posts putting citric acid through the radiator will damage it. You're meant to isolate the rad when running citric acid through thr head and block.

[svenedin]

Just thinking out loud , could you run the engine with citric acid as coolant, will circulate it and bring it up to temperature...maybe the only downside is that the radiator fins might not like it ?

John ;-)

From what I've read in older posts putting citric acid through the radiator will damage it. You're meant to isolate the rad when running citric acid through thr head and block.

The old Holts Radflush was a two part, two step process. As far as I know, part one was citric acid and part 2 a neutraliser. It seems to have been replaced with “Speedflush” which is not a two step cleaner.

Citric acid should be ok to run in the complete cooling system at least to get the engine up to temperature. It would need thoroughly rinsing out of course. I think the metal at risk is the brass in the radiator but citric acid can actually be used to clean brass. Prolonged contact is probably a bad idea. I think people have blamed cleaning chemicals for causing their radiators to spring leaks when what has actually happened is the chemicals have dissolved the crud that was blocking leaks that were already there.

[Dougie212]

Thank goodness I found this post. I’ve removed the thermostat today and found it to be solid with crud. I haven’t ventured yet to look for the drain plug on the block but will have a look over the weekend and see what kind of a state it’s in. Thank goodness for this forum yet again!

[davidpidge]

Couple of weeks ago I put a load of x800 (central heating system flush) in and ran the car around a few times over the weekend. It doesn't seem to have made a dent on the blocked block. The radiator still has clean water running through it so the coolant is definitely just pumping around the front of the engine and not around the back. The heater pipes are also very hot.
The engine gets hot quickly after a short drivw.
Am I looking at an engine strip down to sort or is there something more hardcore than citric acid/flush that will eat through anything in there?

[svenedin]

I didn’t think X800 central heating flush contained any acid?

[davidpidge]

No it's quite gentle and can be flushed down the drain so I wanted to give it a go before ordering anything online.

[svenedin]

No it's quite gentle and can be flushed down the drain so I wanted to give it a go before ordering anything online.

Well you could run citric acid (dissolve in water first) through the cooling system. That can be thrown down the drain too. I think using inorganic acids (e.g Hydrochloric) would be a very bad idea. Physical attack and citric acid is the best you can do I think.

[panky]

CLR (calcium,lime scale and rust remover) is safe in your engine. Screwfix sell a litre bottle for about a tenner.Safe to leave in for a few days.

[oliver90owner]

Have I missed the possibility of a blocked radiator being the problem? No way would I be removing the cylinder head as a means of sorting this problem, unless I knew, to a fair degree of certainty, that it was the problem.

The mayonnaise makes it a little unlikely, but we don’t know how the engine is performing otherwise.

I would first be checking the radiator to see if it has blocked tubes - easily done by removing the fan and feeling the radiator after the thermostat has opened fully.

Circulation flow would be the next check - good flow across the radiator header tank is a fair test - it could be a failed water pump impellor?

Cylinder head gaskets are rarely the cause of over-heating - unless blown - evident from being clearly obvious to obvious with a compression test. Bubbles in the radiator header tank is easy check, if there are no compression resting kit available. Unless the engine is very clogged with scale, from (generally) years of running by draining instead of using antifreeze.

Can’t check this post ‘cos I’m going out fro the day in a few minutes.

I have knocked out wet liners, before now, where the rear pot was totally encased in deposits, so it can happen.

[davidpidge]

Water pump is new. Radiator has been flushed through multiple times now and is totally clear top to bottom. Top and bottom hoses get very hot once engine heats up.

Here's a photo from when I replaced the water pump. Might help to give an idea of the blocks condition!

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