Draining antifreeze before changing intake manifold

[ChuckN]

The answer is…obviously. So, I just replaced an oil pan gasket and refilled the oil and put the antifreeze back in the radiator after “fixing” the temp sensor. As it turns out, there’s a casting flaw in the intake manifold and it’s weeping out through pinholes near the gooseneck/ temp sensor- standard Performer intake.

I haven’t taken an intake off a SBC in years- the radiator has a petcock that I can drain it completely, but will that still leave a bunch of antifreeze in the intake/block that will ruin the fresh oil? I can’t remember doing that with my dad years ago- I think the 305 in my old Nova was dry and hadn’t been driven in years so we didn’t have to worry about it. Fast forward 30 years later, and here I am- just thinking about the process and not sure if draining the rad and removing the hoses will get the fluid level low enough.

Thanks in advance!

 

[Ontheboulder]

The answer is…obviously. So, I just replaced an oil pan gasket and refilled the oil and put the antifreeze back in the radiator after “fixing” the temp sensor. As it turns out, there’s a casting flaw in the intake manifold and it’s weeping out through pinholes near the gooseneck/ temp sensor- standard Performer intake.

I haven’t taken an intake off a SBC in years- the radiator has a petcock that I can drain it completely, but will that still leave a bunch of antifreeze in the intake/block that will ruin the fresh oil? I can’t remember doing that with my dad years ago- I think the 305 in my old Nova was dry and hadn’t been driven in years so we didn’t have to worry about it. Fast forward 30 years later, and here I am- just thinking about the process and not sure if draining the rad and removing the hoses will get the fluid level low enough.

Thanks in advance!

you should be good if you drain the radiator and pull the bottom hose off. might get a dribble in the lifter valley nothing you can't get with a rag or paper towels

 

[ChuckN]

you should be good if you drain the radiator and pull the bottom hose off. might get a dribble in the lifter valley nothing you can't get with a rag or paper towels

Thanks! I’ve been getting conflicting information.

 

[fast 99]

When the intake is removed do not rock it from side to side or end to end, just as straight up as possible. You will likely get some spillage but if careful should be ok.

I usually do not install the thermostat until the air is bleed out. It's an easy place to see if it is full of coolant.

 

[Ricko1966]

@fast 99 a little trick for you wedge the tstat open with asprin. You can fill it no air lock,the asprin devolves 1st time you get it warm.

 

[fast 99]

@fast 99 a little trick for you wedge the tstat open with asprin. You can fill it no air lock,the asprin devolves 1st time you get it warm.

Yeah, that's a good one. Usually have aspirin in the toolbox for dealing with intermittent drivability problems.

 

[PrairieDrifter]

Watch the oil once you start driving it. Sometimes it's quite a bit of coolant at the back water ports on the heads.

 

[SirRobyn0]

Thanks! I’ve been getting conflicting information.

In my opinion you get conflicting information because it's a matter of opinion for the most part.

If you are careful can you get away with it, sure I'm sure you can I've known guys who have. Would I? No. Here's my thinking. You pull the intake off and may or may not get much coolant in, if your careful it'll probably be a small amount and heat will take care of it after a run or two. But what about anything not coolant that gets in the valley. If this is an old motor there's going to be at at least some dirt, and what about scrapping off the gasket material from the head? So being a good mechanic you jam some clean rags in the valley to collect that stuff and then vacuum out the valley before reassembly.

Good enough. Probably. I always like to fire up the motor after a job like that, let it warm up a bit, at least enough for the oil to thin some and then drain it and put a new filter on.

My thinking has always been that oil and filter is cheaper than a motor if something is inadvertently left behind that is not good. If your running some pricy flavor of oil consider draining it out in a clean catch can, pull the filter, install a cheapy, and cheap oil, then after the first run and drain, put the good stuff you drained out back in.

Short version, would I do the job without an oil change? no. Can the job be done without and oil change and get away with it? If your careful probably. Is it worth the risk? Only you can decide.

 

[ChuckN]

In my opinion you get conflicting information because it's a matter of opinion for the most part.

If you are careful can you get away with it, sure I'm sure you can I've known guys who have. Would I? No. Here's my thinking. You pull the intake off and may or may not get much coolant in, if your careful it'll probably be a small amount and heat will take care of it after a run or two. But what about anything not coolant that gets in the valley. If this is an old motor there's going to be at at least some dirt, and what about scrapping off the gasket material from the head? So being a good mechanic you jam some clean rags in the valley to collect that stuff and then vacuum out the valley before reassembly.

Good enough. Probably. I always like to fire up the motor after a job like that, let it warm up a bit, at least enough for the oil to thin some and then drain it and put a new filter on.

My thinking has always been that oil and filter is cheaper than a motor if something is inadvertently left behind that is not good. If your running some pricy flavor of oil consider draining it out in a clean catch can, pull the filter, install a cheapy, and cheap oil, then after the first run and drain, put the good stuff you drained out back in.

Short version, would I do the job without an oil change? no. Can the job be done without and oil change and get away with it? If your careful probably. Is it worth the risk? Only you can decide.

I’ve been working so haven’t been on the forum- but long story short, I realized I still had the jug from the clean new oil. Knowing myself, I figured I’d slop something down the valley, so I took the time to drain it back into the jug. I’m sure that people do it without issue without contaminating the oil all the time- thinking back, I know my dad did. I even have an advantage since mine is freshly rebuilt and I won’t be scraping oil cruddy sludge while I’m in there.

As for oil- nah, standard Valvoline 10/40 with Lucas ZDDP added during the break in ( might just stick with that combo anyway).

New Performer RPM showed up last night and I have everything ready to go- only thing left to do is take off the old faulty manifold itself. Hope to have it running next week. How many times have I said that before?

 

[mrdap]

If I were doing this work I would pull the coolant drain plug from the block and drain all the coolant out of the block before removing the intake manifold.

 

[ChuckN]

If I were doing this work I would pull the coolant drain plug from the block and drain all the coolant out of the block before removing the intake manifold.Nob

If I were doing this work I would pull the coolant drain plug from the block and drain all the coolant out of the block before removing the intake manifold.

Job is done as of today. I drained it last weekend, and apparently over the week it had enough time to get low enough to not be an issue. When I pulled the intake today, didn’t see a drop. Good information though.

 

[mrdap]

Excellent. Glad it worked out for you

 

[75gmck25]

I’ve replaced an intake a couple of times and just used the radiator drain for the antifreeze. Never saw any antifreeze remaining in the intake or heads area, other than a few residual drops.

 

[ghopp24]

I use a shop vac to suck out the antifreeze. Gets it all.

 

[Ricko1966]

I use a shop vac to suck out the antifreeze. Gets it all.

I had a customer who used a shop vac to suck gas out of his gas tank. Seriously, I can't believe anyone would ever think this is a good idea,it isn't. It did not turn out well.