Cylinder head gasket sealant

[lazyb5]

Hi all, been reading my manual before putting new gasket on tomorrow, and there's one area which says place sealant according to diagram. We'll the diagram is very poor or I'm bad at reading it. Anyone any got any idea please.

[Simon Jones]

I'd recommend Wellseal on all mating surfaces. Worked for me .

[Northern Bongolow]

I'm bad at reading it. Anyone any got any idea please.

should go to you know where mate. good luck with it.

[rita]

The sealant goes on the front of the block area covered by the lower torqued bolts "a",it should be quite clear if you have a good look at it, the rest of the gasket does not need any sealant owing to the high torque.

[mikeonb4c]

The sealant goes on the front of the block area covered by the lower torqued bolts "a",it should be quite clear if you have a good look at it, the rest of the gasket does not need any sealant owing to the high torque.

I thought Simon used it on all mating surfaces including the gasket, just for belt and braces, and the job came out good.

Simon - have I got that wrong. Conventional wisdom is gasket shouldn't need sealant but.

[Simon Jones]

I used it on both sides of head gasket, as recommended by Bellhill Garage who have been repairing Bongos for many years. My engine has since done well over 15,000 miles with no issues.

[rita]

Its really up to the individual on what they uses and on how confident that they are on the work that they have carried out, you need to be very careful using sealants on Multi Layer gaskets for obvious reasons.

Its your engine its up to you.

Good Luck.

[helen&tony]

Hi
I tend to agree with Rita...My Dad always said grease the gasket to allow movement during the tightening ...It's always worked for me....BUT, it would be advisable, as Simon always mentions...DECK THE BLOCK to ensure it's flat!
Cheers
Helen

[Simon Jones]

In case I've missed something, what are the obvious reasons?

If you have a perfectly flat block and head then the need for sealant is minimal which is why is Mazda don't use it at manufacture. However, a cylinder head that's been skimmed flat and then refitted onto a 15+ year old block that may have a distorted or pitted mating surface is going to need all the help it can get to ensure a reliable seal.

I've refitted a skimmed head and it simply would not bleed as there was still combustion gases getting into the coolant. Same head refitted using Wellseal on a decked block was perfect and is still going strong 6 years later. Only difference was a few hours hard work dressing the surface of the block and a tube of goo developed by Rolls Royce who know a thing or two about building engines . I'm happy that it was the right solution for that particular problem, but other folk should follow their own instincts and take whatever actions they feel is appropriate based on their unique situation.

[lazyb5]

Hi all, well I took Simons advise and used stag well seal, I used it due to the fact it looks like the original head and was pitted in a few places. I also was really careful getting the old gasket off, I used brasso to try and polish the old carbon off. I must say well seal spreads superbly loads better than hylomar blue. George at bongo spares sent the turbo today so tomorrow's job is putting ancillaries on and all new hoses. I also took the injectors for a clean and refurb so we will see what it all turns out like. Easiest job so far cam belt undo the cover , take off the tensioner , replace the belt replace with new tensioner check timing marks with mirror, replace cover simples

[helen&tony]

Hi
Simon...
I'm not arguing, but I wouldn't re-use a Mazda head...I really think that a properly matched pair of mating surfaces need no gasket at all IF they do mate properly. If the 2 surfaces are dis-similar metals, then they may need a gasket to cope with the differential expansion rates.
Rolls -Royce know a bit about engines, true...and it's a firm that don't make car engines , more is the pity...The car engines are supplied by BMW, as they own the Marque. BMW engines probably need sticky stuff to hold them together
Seriously....getting back to the thread, I think skimming an old Bongo head MIGHT work in some cases, but what's become apparent over the last few years, is that warping and burning between combustion chambers isn't the problem...it's the cracking round the exhaust seating area, so from a purely personal viewpoint, the head needs replacing once it's had a heat-up!....and only with a quality head!
Cheers
Helen

[teenmal]

Hi lazyb5 ,don't know whether you have but its advisable to run a Steel Straight Edge over the block and head using a back light before reassemble.

Good Luck.

[Simon Jones]

In think in my case, I was fortunate as there was no overheating involved. It was a 5 minute drive across town & when I stopped the coolant was coming out of the overflow. After many hours of bleeding it was apparent there was problem with pressure getting into the system. Took head off, skimmed, pressure tested OK & re-assembled = same problem. Took head off again, pressured tested (hot) somewhere else & it was still ok. Decked the block, applied Wellseal & re-assembled with no more problems. It looks like it was a simple case of the head gasket failing but if I'd continued to drive with low coolant it would have gone to a full-blown overheating incident.

I didn't have a low coolant alarm at the time & even if I did, as the coolant level was raised due to being pressurised it would not have alerted me to a problem until a lot of coolant had been lost. From that experience, I made a simple high coolant alarm which activated when water passed through the overflow pipe. This saved the day in Poland when I got air in the system due to a nick in the (brand new) bleed tube which was drawing in air whilst driving. It was a bit scary as I feared it was something more serious, but once the cause of the problem was identified & it was re-bled there were no further problems.

Shortly afterwards, Haydn brought out a high coolant add-on which I fitted in place of my own unit. Unfortunately, very few other owners saw the benefit in having this so there were only a limited number produced. This is a shame as it would undoubtedly have given early indication which may save a number engines which have gone on to overheat after coolant has been forced out the system. It certainly would have alerted me to both the incidents I experienced.

Fingers crossed for lazyb5 that when it's all put back together that all the hard work has paid off.

[mikeonb4c]

Yet again Simon I have to say you make your point very well. As with life, there is how an engine should be, and there is how it actually may be. Hopefully, lazyb and other head refitters will benefit from your successful experience.

[helen&tony]

Hi
Simon...
I have one of Haydn's High coolant alarms...always be on the safe side!...and, yes, they can be a tremendous help in the circumstances when over-pressure without over-heat actually occurs
Regarding not re-fitting a head, as I said, It's personal preference, because not many cases of damaged blocks occur on the Forum, and a grand or so on a new head and the cam / timing gear, etc. must be able to give a total new lease of life for a considerable period...I think that's the only thing that I dread over here...most of the rest can be sorted by the local lads!
Cheers
Helen