Thread: Welch Plugs

what sort of locktite? I would use 515 gasket sealer a bit more forgiving on any gaps were the plugs tight going in? metric or imperial plugs used?

Originally Posted by Keithy P38

................................................. I used a bit of light wet-n-dry to clean the holes before they went in, then a gentle smear of loctite on the new ones before I fitted them. They went in straight and easily.

Keithy

Hi Keithy, define 'easily' , welch plugs should go in 'quite firm' to 'tight'.
A good idea to clean out the hole before hand but not to be too aggressive about it. The welch plug must be a tight fit, you need to drive it in with a hammer. I use a suitable sized socket that fits into the welch plug so that it's 'pulled' into the hole pulling the sealing surface in allowing it to easily 'compress' to have a good fit, as opposed to either belting it in using a socket (or worse just the hammer) on the outer welch plug lip which 'expands' the sealing surface when it really needs to 'compress' to go in. I hope that makes some sense. I use common or garden variety gasket cement to act as a sealant and lubrication on fitting. Don't use silicon as the 'scraps' tend to clog up radiators.

Why did you change to 'red' (OAT) coolant in the first place ?, this stuff is absolute death to a system which has any 'green' (Ethylene Glycol) stuff left in it and can destroy internal seals/gaskets etc. in a vehicle not specifically designed for it. Marketing hype and bull**** aside I can't think of any good reason to 'move' to red coolant. Google 'Dexcool' for a good, err......bad read.
Some manufacturers claim 'red' coolant to be compatible with 'green', I wouldn't believe this for a minute with the exception of the greedy incompetent fools that made OAT coolant and dyed it green , these bastards should be shot. Basically, If your vehicle has 'red', 'green', 'blue' (or whatever) coolant, keeping it that way is probably a good idea.

Put simply, red coolant can be poison to a system designed for green. Now that you've 'poisoned' your system I don't know if it will cause (further ) damage if you return to a glycol based coolant. You'd certainly have to rinse every last drop of red stuff out. Others may have a better idea.

Deano

I've not had the welsh plug drama as yet so this is timely I guess.
I'm not sure of the composition of the OEM plugs, although my instinct tells me to steer clear of dissimilar metals..

With brass and aluminium, the aluminium will tend to go into solution before the brass... that's why you need sacrificial metal plates on aluminium boats with brass props.

The silicates in "red" OAT coolant are not generally compatible with brass and you can get a red sludge ... hence aluminium cores and plastic top/bottom tanks on OEM radiators.

I wouldn't go back to green coolant but rather see if you can get hold of some aluminium welsh plugs. When refitting, use some "green" Loctite (stuff used for fitting bearings to shafts).

cheers

Thanks for the replies lads.

By "easily" I mean that with a socket and hammer they went in straight and did not give any grief.

The welch plugs were imperial (from memory they are 1 1/4"), same as the old classic 3.5's and 3.9's. They were a perfect fit.

I'm thinking that brass may not have been the good choice (although I'm not sure what metal the old ones were, but they were very corroded - hence the original leaks).

I made the change to red coolant a few years ago, based on what I read in the owners handbook. It said something about phosphate free with ethelyne glycol mix (this is going back 3yrs). I flushed the entire system, drained and flushed the block and heater core before I made the switch. I got 2yrs out of it before the welch plugs started to drip! Even now, it's only a drip on the ground every now and then, but it's definitely coming from the plugs!

If I can't find ally plugs, should I go back to green?

Cheers
Keithy

My advice FWIW is definitely don't go back to "green" because it's not optimal for aluminium engines. While the basic ingredient is ethylene glycol in both the OAT and "traditional green" coolant, it's the additive pack which changes the chemistry depending on whether you have iron or aluminium blocks and/or heads. I've always used the Holden red stuff specified for LS1 engines (well I can pretend!). You may need to hunt around for the plugs. Perhaps try a couple of engine recon places and see where they source their replacement parts?

Might be the go hey! For what it's worth, they are not leaking bad, it's bugger all really, but I am not one to let something build up until it becomes a problem.

Being honest, the welch plugs are probably 15 years old anyway. They've done well!

Do you remember what welch plugs you ordered ? There a leaky brass plug on the back of the drivers side head on the motor I'm about to fit. I'm trying to decide if I'm better off trying to seal up the existing plug .... or replace them all ( as will the new one leak worse once the motor is fitted back to the car

Its a bugger of a spot to have to redo if the plug doesn't seal as you would need to pull the motor out again. I'm guessing it would pay to do the plugs behind the flywheel while I'm here? (unless they never fail of course .... in which case leave well alone!).