boonie

iam going to clean my cooling system in my 94 within the next couple of weeks and i want to clean my cooling system using by back flushing it using the Prestone back flush kit, is this a good idea or a bad idea?.
your experiences will be appreciated.
boonie

LT1CORVETTE

I wouldn't. I just did my 96 about a month ago.
Definitely remove your surge tank and rinse that out really well with a hose or in a sink. I could not believe how much junk kept coming out of that thing. Remove overflow and clean that out well. I had my fan shroud off so I pulled and flushed the radiator with a hose (not necessary and removing the shroud is a PITA). Then put everything back together. Removed the thermostat from the water pump (needed to replace it, but a good idea regardless). Put the housing back on. Filled the system with distilled h20. Ran it for a few minutes then fully drained the system. Draining from radiator and knock sensors. Then put a shop vac blowing out in the surge tank. Refilled with distilled h2o and repeated once more. Water was very clean by this point. Put the new thermostat in, refilled with water/dexcool/water wetter. Coolant system is operating great.

This approach takes time. But if you are willing to put it in, the results are really good.

josephf31

have used the Prestone kit on many other cars for years and don't see why it would be a problem. It's a Chevy small block!

NEVRL8T

If you use a shop vac to blow out the coolant then I don't think you need to remove the knock sensors.

onedef92

If you remove your thermostat (much easier to remove than the knock sensors) then use the Shop Vac to blow the coolant out, you don't need to remove them.

NEVRL8T

Julian, what horse shop vac do you use?

Aardwolf

Shop vac will not get debris down by the knock sensors.

onedef92

Mine makes 6.5 peak HP. More than enough punch to evacuate the coolant from the block and heater core, too.

onedef92

Who neglects their coolant system to the point debris is floating around in there? I service mine annually and my coolant always comes out GREEN, not brown.

JeepCycle

Apparently the 6 "A"Holes who previously owned my '85!!!!

onedef92

Well, those knock sensor holes aren't that big, either. If you've got debris that's too big to come out of there, aren't you still SOL? A backflush won't dissolve rust and other metal debris will it?

Aardwolf

Lots and lots of folks do. IMO by not using the drains, in a way you are too.

ekess744

make that the 4 before me

LT1CORVETTE

And the two before me and including me as I had previously had two different shops flush my system.

When I used the shop vac I used it with the knock sensors removed. Really didn't do much as they system was empty, but moved a little more coolant out.

samsonb

Where are yall putting the shop vac on the L98? Thermostat opening with the drain plugs removed?

I was thinking of pulling the knock sensor plug, cooler lines, and heater hoses. Then run water through the heater core for a front and back flush. Then run water through the thermostat opening and run water through the heater hoses going into the block.

Just wondering if that would be the best way to flush the block out instead of draining/refilling and starting/stopping multiple times?

Mark_Sheehy

I put one on my 89 8 years ago and have never had a problem. In fact if I lift it up a little bit, it is the highest point in the system so I do the initial fill of the block from there.

combustables

I would NOT use that on an L98.

I did it three years ago when I didn't need to and the car started running hotter immediately after I did. It didn't exactly overheat but it was always WANTING to over heat if I didn't hit an open highway stretch.

I used to be able to idle with the A/C on and soon after I flushed I could no longer do that. Any idle for more than 4 -5 minutes would get me closer to 230 than not.

Since then the engine was completely taken apart and put back together again (polished manifold, Plenum, runners etc) and it;s been running absolutely nicely since. I can use the A/C and idle again.

A very good mechanic explained that flushing might have dislodged a piece of gasket that clogged up a coolant passage. That would have been the only plausible explanation to what happened.

I would NEVER flush anything again. I would drain, fill, drain and fill again etc. Water hose pressure could cause unwanted results. I hope my experience benefits someone in their decision making.

GKK

I used the Prestone flush kit on my previous "91" Camaro, "89" Vette and my current "91 Vette all with Great results.

If you can see visible signs of large debris floating around, you should first drain the cooling system completely including removing the Knock sensor, before installing the flush kit.