so am ready to get a flush on a 95 and called couple outfits to see how they do it and keep hearing they just recirculate coolant thru the system, so I ask if they drain the block and they shake their head saying they just recirculate the fluid.

according to some guys on here say you need to pull the knock sensors to drain the block..............question is will either method work??

 

I bought a Prestone flush kit about 2006 and did it. The T-Connetor is still in place today holding tight...actually just had it done again at my garage and the mechanic said he used the same T-Connector! I didn't see the need to pull and knock sensors, just recirculated.

https://www.walmart.com/ip/Prestone-...&wl13=&veh=sem

 

I did the same as bac22. No issues and the "T" fits in nicely, barely noticeable.

 

When I changed my original water pump this spring I flushed the block at that point with the water pump off.

 

My $0.02 - I ran into some overheating problems on a 92 LT1 that I had bought used and took to the track. Four relatively gentle laps in - the coolant temp read 230. I had trailered the car up and I trailered it back home - and the next weekend, I started tearing into the cooling system. The fluid in the plastic overflow reservoir looked beautiful, I drained the radiator and the fluid that came out wasn't great - but it wasn't horrible looking either. Then I pulled the two block drains - what came out was much closer to black than green. Truly ugly !!!!!! I also pulled the rad and cleaned up the junk that had accumulated between the condenser and the radiator. Finally - I disconnected the heater hoses and flushed the heater core - what came out wasn't real nice looking either - but nowhere near as bad as what came out of the block drains.

When I put it all back together with fresh coolant - the overheating problem was gone !!!

I really doubt that any flush kit would have been able to get the junk out that pulling the block drains (a.k.a. knock sensors) did. Pulling the block drains isn't a fun job, and you need to expect that a lot of the coolant that will come out will not be "catchable" - so it's probably best to do it outside (don't do it with hot coolant, and plan to take a shower afterwards - as it's likely that the coolant will get all over you) But I'd say that it is absolutely THE BEST way to get the crud out. I'll also say that the stuff that came out of the block drains last was the worst of what came out.

No mechanic is going to pull the block drains - it'll take them almost an hour - and no one wants to pay for an hours labor to do a coolant flush - plus it'll make a mess in their shop. There are MANY shops out there that just do a radiator drain, refill with fresh coolant, and call it good ...

Obviously your call if you think it's worthwhile - but if you're really trying to get all the crud out - I would say that pulling the block drains is absolutely worth it.

 

thanx for the info but when they say recirculate new coolant does that not suck anything out of the block ???

 

I changed the coolant in my 94 yesterday. When I pulled the knock sensors there was minerally looking sediment that came out.

 

how old was the coolant?

 

~8 years

 

I pulled the knock sensor to drain the block before replacing the heads, there was a LOT of heavy material in there. Rust and scale. I honestly don't think that would have come out any other way.

I used DEXCOOL coolant to refill it. I'm a big believer in that stuff. I replaced a water pump on a silverado pickup that had almost 300K on it, and there was no rust in it AT ALL. So, that sold me. It's all I will use now.

 

When I did mine it was like others have said, black and brown sediment. Can't say how old the coolant was as I changed it when I bought it.


I guess I don't see what the big deal on pulling the Knock sensors is? On mine, working on jack stands, it took all of 10 minutes to pull them. While it takes a large socket, any shop worth letting touch your car should have no trouble removing them.


Maybe the 92's are just easier to get at than other years, don't know.

 

8 yrs???!! surprised it didn't turn into sludge

 

Sure the flush kits will push some coolant out of the block - but the flushing process doesn't seem to do a good job getting the crud that builds up towards the bottom of the block. It seems that the way the coolant circulates through the block is far from uniform. Look at the location of the water pump, and where the coolant exits the heads / intake manifold and moves to the radiator. There is not much flow towards the lower part of the water jacket around the cylinders.

Look at what the other posts are saying - I'm not the only one who has experienced this crud coming out of the block drains.

Bottom line - it's your car - do whatever you want. These days most people (and by that I DO NOT mean those who frequent this forum) seem to think that extended life coolant means "forever coolant", so even just draining the radiator and getting some new coolant into the system is a lot better than most cars get. Flushing the aystem using one of those kits is better yet.

The truth is that ethylene glycol doesn't wear out - it will keep water from freezing 20 years from now - but the coolant you buy has more than just ethylene glycol in it - it also contains an additive package that includes corrosion inhibitors. To oversimplify - some of the corrosion inhibitors are essentially sacrificial, so they do lose effectiveness over time, and getting new antifreeze in there will really help reduce the potential for corrosion !!!!

But quite a number of people have reported seeing lots of crud come out when the block drains are removed - particularly on cars where the previous maintenance has been less than perfect. Again - do whatever you think I appropriate and what you have time for - but if you're looking for opinions - you now have several....

 

It should also probably be mentioned that not all antifreeze is compatible with every other anti-freeze these days.

So, it's probably good to run some water through the heater core, block, rad, and stuff to get it all out. Then refill with your preferred brand and stick to it or AF's that work with it thereafter.

It ain't all the same anymore and mixing it can cause problems.

 

The only thing I wonder is you're not supposed to leave tap water in the cooling system, but what else would you flush it out with?

 

Personally? I didn't flush it with anything.

I used the concentrate (that you dilute with water) and just figured there was several quarts left in the system.. And filled it up with straight anti-freeze.

It tested fine?

 

PS: That was on my truck. .

On the car, there wasn't anything left. I had the block drains out. Rad was new. Heads off. WP off.

There couldn't have been very much.

 

I would never run Deathcool in anything other than a GM vehicle currently under warranty.
I would NEVER put it anything without a pressurized tank.

 

Really? Why?

I'm dead serious. I pulled a water pump off a 5.3L at 277K and it was perfect. No rust anywhere. It looked like brand new!

Very impressive. Nothing bad happened in my vette yet, it's been a coupe of years. Truck is fine too.

Is there a reason you wouldn't use it? I'm just going by what I witnessed. I dunno if there's a further, technical, reason not to.

But WOW! The corrosion protection must be first rate!

 

When i pulled my block drains, there was so much crud in the engine... I had to poke at it to get it to even start draining.