'99 Prado 3.4 5VZ-FE coolant/water leak

fred99999au
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'99 Prado 3.4 5VZ-FE coolant/water leak

Unread post by fred99999au » July 3rd, 2015, 6:15 pm

Hi All. My wife's 99 Prado developed a massive coolant leak and it appears to be coming from behind the LHS cylinder head cam belt cover.

It wasn't run for too long like this so I am hoping it isn't a cracked head.

Anyone know what lives behind the cam cover on the LHS that might cause a large coolant leak?

I'm thinking it might be a welch plug, but I am guessing only.

TIA for any sage advice.

Fred.

fred99999au
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Re: '99 Prado 3.4 5VZ-FE coolant/water leak

Unread post by fred99999au » July 5th, 2015, 7:24 pm

Turns out it was a welch plug in the cylinder head. Mongrel of a job to repair for the cost of the $2.35 part.

Needs cam drive pulleys and everything in front of them removed, so you need to set the cam timing as well.

I could now do the job in about 4-5 hours I reckon but the extra day of learning was painful, especially in the rain pulling it all down. Welch plugs are 30mm OD for anyone interested.

Peter Aawen
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Re: '99 Prado 3.4 5VZ-FE coolant/water leak

Unread post by Peter Aawen » July 5th, 2015, 7:59 pm

Good thing you found it & sorted it tho!! How many km does the engine have on it?? What caused the welch plug to give up?? Old age, or corrosion due to earth leakage, incorrectly mixed coolant, or something else odd?? If it's a relatively low km motor, it might be worth checking out the cause?! :thumb:
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fred99999au
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Re: '99 Prado 3.4 5VZ-FE coolant/water leak

Unread post by fred99999au » July 9th, 2015, 7:10 pm

Dunno Peter. There are two plugs on the front end of each head and they seem to be in segregated sections of the water gallery, i.e despite being 15mm from each other they are in different parts of the water gallery.

I pulled the failed bottom one out and it was well corroded. I popped out the one above it and it was like new. From this I suspect it may have had an anti-corrosion coating damaged before installation at the factory. The new brass ones will outlast me.

The vehicle has around 250,000 on it.

I did however discover a way of compressing the cam belt tensioner using nothing more than a tirfor winch handle, a ratchet strap and a Yamaha IT175G fork leg...
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