Inlet manifolds helicoil

[Mike J]

Just about to repair and helicoil the inlet manifolds, two of thetop bolts not tightening. Is there anything I should be aware of ?Also should I use a silicon gasket sealant or just fit the new one dry. Mike

[GDPR]

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Wellseal is better. Silicone squeezes out too much and can partially block the waterways

[dasadrew]

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been a couple of detailed threads (sorry for the pun) on helicoils in the last few weeks. Do a search on "helicoil" and you should find lots of stuff about "how to" etc.

[Mike J]

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Thanks for the replies. The helicoil part isn't the problem its trying to get the correct torque on those hidden nuts that could be the issue. Do I apply wellseal to all faces. I have some locktight blue stuff is this any good. Mike.

[Stagdad]

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I'd get Wellseal if i were you

Cheers Steve

[mattsay]

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Hi Mike,

As I have just fitted a replacement water pump (and therefore had to remove the inlet manifold) I can speak from very recent experience on this one.

Firstly Block the inlets holes with kitchen roll or rags to stop swarf entering. Have a vacuum cleaner on hand to suck it all away.

Make sure you don't drill too deep or you will be into the waterway before you know it. Previous owner went straight through, thankfully only one. Also make sure you drill at 90 deg to the heads. Take your time.

The helicoil is 5/16" UNC (UNC in Ally, UNF in steel). Use oil or cutting compound to cut the new thread with the tap. Really take your time cutting (one 1/4 in to cut, at least half a turn to a full turn back out to clear out the swarf- the more clearing the better the thread quality eventually).

Make sure the helicoil goes in tang downwards (I tried it first the other way up and had a problem). The helicoil should be 1/2 to 1 full turn below the surface of the head - it shouldn't be proud. Make sure you remove the tang as this is what secures the helicoil into the hole properly.

Use Stag Wellseal to "seal" the gaskets. Use Payen gaskets, they are worth the extra money. I tried cheap as chips ones first and then did it all again to stop the leaks. Some people recommend clamping the gaskets to the manifold using blocks of wood and clamps overnight. Some say fix them to the heads and leave overnight. Others say just get on with it. I left mine overnight on the heads. Foud that they had moved slightly and needed tweaking the next day. I would now subscribe to the get on with it lot, just make sure the gasketsare aligned properly when fitting the manifold bolts. It's better to screw the bolts in by hand at first to make sure you are not cross threading and you will soon know if you are trying to start the thread into the gasket as well as your new helicoiled threads.

I was amazed that even with Payen gaskets and Wellseal how tight the bolts need to go to have a weep free manifold. It's very scary thinking you might just about to be needing more helicoils! This is why people recommend helicoiling all the holes / threads. It will be very annoying to get to the last bolt and have to take the whole lot off and helicoil another thread. I got away with it, but others will talk from experience and say do them all.

Tighten the bolts a little each in turn and gradually torque them up.

If at the end of it you still get a small weep and a little coolant in the "V", don't despair. If you buy some K-Seal (about £7 online) it will stop any leaks of this type and indeed much bigger ones in the short term. My pot / bottle is still unopened as yet but the car hasn't really been tested yet on a full high temp run.

Last piece of advise. Some manuals say loosen one of the heads when refitting the inlet manifold. That's rubbish. Don't disrupt a perfectly good head gasket for the sake of themanifold.

Hope I haven't missed too much. There are plenty of better spanner wielders than me on this great Forum. I'm sure they will jump in with advice. The above worked for me so far though.

Best of luck and be patient. Apologies to those who fell asleep half way through reading this post.

Matt.

[mattsay]

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Hi Mike,

Matt again.

During my posting "war and peace" I see you asked about the sealant again. Use the Wellseal on the surface of the heads and then also on the gasket faces that mate with the manifold.

With patience you can do up all the bolts with a socket (1/2 inch from memory) or a spanner. The two awkward ones are the upper right on the left hand side and the upper left on the right hand head. It takes as long to do these two as the rest put together. Sometimes it feels you are moving them less than a mm a time, using the open end and and then the ring end often in turn just to get on the heads to move them - another reason for making sure the gaskets (bolt holes) are well aligned, so you can do up the bolts by hand as much as possible.

Cheers,

Matt.

[nib]

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A tip for tightning the two awkward bolts,grind down an open ended 1/2 inch (both sides obviously) which will make it easier to get a decent turn on the bolt,swap over with a spanner with more meat on it to finish off.

Mark

[mattsay]

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Good shout Mark.

[Mike J]

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Brilliant that's so kind of you. I found a "Stepped" 1/2" ring spanner got to the awkward ones. Think I will replace the gasket on the thermostat whilst I'm there. Hopefully I have only one top thread to helicoil Have some left over from refitting the intake elbows. Thanks to everyone again. Mike

[elvimto]

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Just a quick update I could not get my manifold back on with standard payen gaskets and I was not going to loosen the head so I made a set of .029 thou gaskets from industrial gasket materialat work, Payen are .055 thou that gave me enough to get all the bolts started and torqued.

Istill think I have a pump seal leak but will not know until the week end.

Stuart

[stag8manod]

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Hi Mike, Do't use cutting oil when tapping holes in Aluminimum, use kerosene or WD40 etc.

Cheers Ian A