Radiator Fluid going down slowly

Most likely cause is a leaking head gasket. Add a small bottle of dark purple dye to the coolant, drive it for a week, then search with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. If you find it inside the tail pipe, the head gasket must be replaced.

Have you checked the heater core?

Thanks for your quick replies. I haven't had the heater core checked yet. My mechanic has assured me it is not the head gasket. He has had it under pressure test now fow 2-3 days and he still can't find any leaks. Can it still be the head gasket? I am praying to just go for a tighter radiator cap for $15 instead of a new head gasket for bigger money. I'll change the head gasket at last resort. Could be anything else other than the head gasket?

Since we know coolant is being lost, add a bottle of dye to see exactly where it's going.

Do i buy the purple dye from an auto shop?

Auto shops should be able to tell you which type to use.

Coolant depleting from recovery tank with no losses from radiator itself is never a head gasket problem.

The most common causes of minutes leaks are hose joints. Check all joints for signs of coolant. When leaks are minute, they sometimes do not leak when engine is hot and at times is the other way round, leaks occurs only when hot.

Will a tighter radiator cap fix the problem or make it worse. Mechanic has had the car under pressure overnight, to find no leaks in the morning, and no drop in pressure. He has found leaks at hoses and the radiator that he has fixed, but the fluid still goes down slowly. I can smell fluid when i stop the car

Auto parts stores have the dye. They will ask what you're using it for so they give you the right stuff. It will say right on the bottle which fluids it can be added to. The bottles are only about an inch in diameter and two inches tall. Many auto parts stores also rent or borrow tools and they will have the black light used for searching for the leak. The dark purple dye will show up as a bright yellow stain under the black light. Follow that stain back to the source. Don't forget to check at the inside of the tail pipe.

Hello Mate. I have the dye for the radiator, but i can't access the radiator directly. Can i pour the dye into the overflow bottle? do i let the bottle run down to empty and then put the dye in? Thanks

Yup, you can pour it in anywhere as long as it will mix with the coolant. I guess I'd wait until the engine had been running and is still warm. The pressure will be gone in 10 to 15 minutes but the reservoir will still be full. Within an hour the coolant will begin to cool down and contract. That will draw some back into the radiator along with the dye. It could take a few warmup cool down cycles but with each one more of the dye will go into the system.

Thankyou. I'll give it a go once i get a chance. Thanks again

I've gotten under the car and yep its glowing under there. There is a small hose with a very slight leek, but where the engine and gearbox meet, drops are forming right on the base. I think its leaking from higher up and dribbling down. I'll raise the car and get under it tonight to find where the leak is higher up. Nothing glowing through the exhaust. GREAT IDEA MATE

So we are getting somewhere. Good luck.

I have discovered 2 places where it is leaking. One is a hose join, this is no problem. The second leak is where the engine and gearbox join. The fluid seems to be coming from the engine side, very slightly along a lower small section of join between gearbox and engine gasket. Any ideas on what is causing this leak and how i can block it up without removing the engine/gearbox. Does it need a new gasket, can i get away with not fixing it or is there an easy fix. Nothing is coming out of the exhaust pipe.

If it was an external leak from the head gasket it should be higher than the transmission bell housing and easy to see. If this is a V-6 engine there will be core plugs on the back of the block that could be corroded through. That's only going to get worse. You can reduce the leak, as I did on an old muscle car, by leaving the radiator cap loose so pressure doesn't build up in the system. Be careful when doing that because that pressure raises the boiling point of the water in the coolant. It's common for the temperature to get above 212 degrees. If yours does you'll need that cap and the pressure it maintains. That is not a fix; it's a temporary measure to let you get by a little longer before getting it fixed.

Thanks for your help and quick response. Is this problem easy to fix? The car is a 4 cylinder model with the motor under the car. Mate i love US Muscle cars, they are worth a fortune here in Australia for a good one.

Four cylinder engines typically don't have core plugs in the rear so lets rule that out for now. Does the dye show up higher up above where you see the drops forming?

The dye does not seem to be coming from anywhere else higher up, dripping and running down. It seems to be oozing out from a very small tight section where the motor joins the gearbox. It is coming out not at the base but a bit to the right, it being a circular connection.

Was there ever a conclusion to this enquiry.

I have a 1991 Tarago (with personalised number plates WOMBAT).
This is my second WOMBAT with both covering approx 350k. I seem to have a very similar problem with about a litre of coolant being "consumed" every 200km. I have had it under pressure up on a hoist. Never a drop of coolant on the painted floor. I had resigned myself to pulling the head - but this trail gives me some hope.

I like the idea of using some dye and will do that.

Fantastic work guys, much appreciated.

Jim

Such problems are due to minor leaks,usueally from hose joints and that is what you should be looking at. The leak is too small to show puddles on the ground.
What you have to look for is signs of coolant which would leave trials oxidised joints, etc.

Many thanks KH, I will get some dye into the system. I like your answer better than pulling the head unnecessarily!! Cheers, Jim

If it is a head problem, the recovery tank would be overflowing instead of depleting.

After putting the dye through my radiator and seen it leaking from:

A hose joint.

And also from the join between the gearbox and engine.

My mechanic has quoted around $300 to fix the welsh plug (which he claims will stop the leak between engine and gearbox).

I'm just going to keep topping up the radiator fluid each month.

Leaks can get from bad to worse so you need to monitor the situation closely.

Topping up each month means the leak is minute and there are stop leak coolants available that might work. Get the type that requires no flushing and is used as a coolant as well.