Y33 Freeze Plugs

[jrichardson]

I believe that I have a leak in one of my freeze plugs. I definitely have a leak (according to the garage floor) and when I pressure test the cooling system, it drips very well. It is dripping near the rear of the engine...by the front of transmission. I checked the manifold "valley" and it's dry. However, I cannot see exactly where it is leaking from, so I am presuming a freeze plug. 185k on the motor.

I've searched the FSM and this site and cannot find anywhere that describes the location of the freeze plugs on a Y33. Any help is appreciated!!

[3Q Jay]

(trying to be helpful)....you really need to get it up on a rack and find the source.
there are drain plugs (threaded) at the bottom of the block on both sides. there were also threaded plugs on the back of the heads on the G50s that would sometimes leak. i don't believe the fgy33 has that particular issue.
there are also heater and throttle body hoses in the back--are you sure it's not one of those?

[jrichardson]

I have a stethoscope camera (whatever those are called) and looked around the throttle body and heater and everything is dry around there.

I noted on the FSM about the threaded plugs on the sides of the block...but couldn't find them while crawling underneath the car.

So...are there plugs at the rear of each head? Do we know if they are threaded or pressed in?

[3Q Jay]

borescope? nice....
here's a picture--not the best quality, but it looks like both threaded and press (freeze) plugs on the back of the VH41DE heads.

https://c-a.d-cd.net/7b555e8s-960.jpg

[jrichardson]

Hey 3Q, that helps! Thanks.

I'm now doubting my diagnosis. Here's why: When I pressurize the cold engine (presume thermostat is closed) I get the leak around the block. If my understanding is correct, there is no way that on a cold engine with the thermostat closed that I could pressurize the system enough to show a leak in a freeze plug in the block. Isn't that correct?

So if that presumption is accurate, then I must have a leak somewhere in the manifold side of the equation, no?

[Skibane]

If my understanding is correct, there is no way that on a cold engine with the thermostat closed that I could pressurize the system enough to show a leak in a freeze plug in the block. Isn't that correct?

When it's closed, the thermostat doesn't provide a completely airtight seal. There is a small "jiggle valve" on the thermostat that always allows some coolant (or air) flow, even when the thermostat is completely closed.



Also, there is no thermostat on the return (bottom) side of the radiator - which means that any pressure applied at the radiator still passes through that bottom hose to the rest of the cooling system.

So, it's certainly possible to pressurize the entire cooling system when the thermostat is closed.

[3Q Jay]

If my understanding is correct, there is no way that on a cold engine with the thermostat closed that I could pressurize the system enough to show a leak in a freeze plug in the block. Isn't that correct?

When it's closed, the thermostat doesn't provide a completely airtight seal. There is a small "jiggle valve" on the thermostat that always allows some coolant (or air) flow, even when the thermostat is completely closed.



Also, there is no thermostat on the return (bottom) side of the radiator - which means that any pressure applied at the radiator still passes through that bottom hose to the rest of the cooling system.

So, it's certainly possible to pressurize the entire cooling system when the thermostat is closed.

I agree.
to OP: any signs of overheat? possible thermostat is frozen shut (except for the trickle thru the jiggle valve)?
Try to borescope just behind the valve covers.
also, see if the leak is coming out of the bottom of the trans bellhousing (as opposed to around the bellhousing). if so, then likely is the expansion plug (s) at the back of the block (below the heads). But I have to say-- I've not heard of expansion plugs going bad in the VH series, and even on the old cast iron detroit blocks, I never saw one blow except for extreme neglect (corrosion), or extreme overheat like a faulty thermostat or driving when the water pump wasn't.

[jrichardson]

Thanks for the information.

The y33 hasn't been neglected, which is good thing. Change antifreeze every 3 years, water pump changed out a couple of years ago. I'm a shadetree mechanic, so I'm decent with my maintenance. The car starting getting hot last week (right in the middle of normal and hot) so that was my alarm. It is leaking around the transmission. I'll borescope around the back of the heads and what I can see.

If I didn't have a leak, I would say that the thermostat was sticking closed. It can idle all day, but will start getting hot after about 30 minutes of driving (that is, before I found this big leak...I'm not driving it any longer until I fix it). Oil is clean.

[Skibane]

When the engine is starting to get hot, can you hear the mechanical fan roaring, after the fan clutch kicks in?

It's not uncommon for the fan clutch to fail - which only allows the fan to spin at a small fraction of its full speed.

[jrichardson]

Hmmm, I'm not sure that I heard that 'roar' that you speak of. I will double check that!

[Skibane]

If the fan clutch is good, when the engine is hot, you'll feel a lot of resistance when you attempt to spin the fan blades by hand (with the engine turned off, of course!)

If the blades continue to rotate after you spin them - for even a fraction of a revolution - then the fan clutch isn't making a solid mechanical connection with the water pump pulley like it should.

When the engine is cold, it's normal to be able to freely spin the fan blades, since the fan clutch doesn't lock up until it gets hot.

[jrichardson]

I found the leak. It's amazing what you can see when you have a little daylight under the hood vs. a dark garage with a trouble light. Leaking on the heater hose attached to the firewall. Couple of twists on the hose clamp and we're good to go.

Refilled with AF, drove it around. It was fine for 30 minutes, then just started to get warm as I was pulling into my garage. Let it sit for 15 minutes and it went to normal. I'm thinking/hoping that it had some air in there and will take care of itself last night as the engines cools and pulls in the AF from the reservoir.

Drove it this morning, very normal...but only drove it to work 15 minutes away. I'll check the fan clutch as you mention. I think I've got this resolved now. Thanks for all of the input.

[3Q Jay]

aha!
make sure you fill the top 'radiator' cap (the one above the block), and leave the actual radiator cap on. fill with engine running t-stat open and heater on max. very common to have air trapped. at this point, i'd probably make sure the upper cap level is full when engine cold (no way to really purge air out of that pocket), and then let the expansion tank do the rest as you suggest.
just curious if you ever hear the 'sloshing' or waterfall behind the dashboard? very common on G50 series when coolant low, but not sure if the fgy33 protests in this manner....

[jrichardson]

No sloshing of AF behind the dashboard, but I have heard that type of sloshing on my 99 Dodge truck.

Drove it longer today...same thing...good for 15-20 minutes, then starts getting warm. It's either air in there or my t-stat isn't opening. Saga continues.

[Skibane]

If the thermostat was stuck completely closed, your engine would also overheat when sitting idle.

[jrichardson]

Solved once and for all. It comes back to what Skibane said. I decided to start fresh and check everything...pressure first, then I let the car warm up, and try to stop the fan with a rolled up newspaper...and it stopped. Put in a new clutch fan and drove it around the customary 30 minutes...no issues. And *now* I hear the roar of the fan. I'm thinking that it must have been going bad for quite a while, but the ambient temperatures pushed it over the limit because I don't remember hearing that roar for a long time. All good! Thanks for all of your suggestions!

[Q451990]

Thanks for letting us know!

[Skibane]

I let the car warm up, and try to stop the fan with a rolled up newspaper...

I like to use a dead cat, but I guess a rolled-up newspaper would also work...

[Q451990]

Or a live cat... if it lives, the clutch is bad, if it's splattered - your clutch is fine.