Radiator Fluid Gunk

This last Saturday my 99 Venture temp gauge began fluctuating wildly from hot to cold over and over while driving, like when air is in the system. I popped the hood and the over-flow bottle was over-flowing, the upper radiator hose was collapsed (it was sucking a vacuum) and the water pump was making an unusual clicking/grinding noise with a frequency related to the engine RPM. With just over a 100,000 miles on the van and 8 years old I have to admit I've never pulled the radiator cap off, I've always simply checked the OF bottle. I pulled the cap and looked like it had been dropped in sand while wet, the inner spring and seats were totally covered in gunk. So here I am with our holiday trip this week and the family shuttle bus feeling sick.

I did the only thing I know to do, which I'm sure was over-kill, I went to the parts store and bought a new water-pump (new design), thermostat, upper & lower rad hose, rad cap and the funky intake bypass hose. I drained the rad core, opened the bleed screws (little brass ones) and pulled the hoses off. I couldn't get to the block bleed screws so I ignored them. Pulled the water pump, it looked OK, still spins w/ no noise, not gunked at all like the rad cap. Then the thermostat (had to remove the exhaust crossover for that one) again, clean, not gunked at all like the rad cap.

Cleaned the OF bottle (it was gunky like the rad cap), flushed the rad core, tryed to flush as much of the block I could with everything disconnected, I stuck the hose into every hole. Put the new pump on (I had it so I used it) and installed the new thermostat (figured about that time) and put on the new hoses. Filled the OF bottle and the rad core with the brass bleed screws open. Closed the screws and ran the engine for 15-20 minutes, while running I opened the bleed screws to let any air out. Everything appears to be good now, temp gauge is where it is supposed to be and the OF bottle is where it is supposed to be.

What did I miss? I figure I still need a proper flush on the system to better clean out the gunk, any recommendations?

In the process of doing the exact same thing on our '99 Venture. We pretty much have the exact same condition. Overheating, (A LOT OF) gunk in the overflow jug, happened a few days before our holiday travels, etc.

My dad has done most of it as I have been busy working on schoolwork and my 'Vette.

We are replacing everything included with the cooling system except the electric fans (they work fine) and the thermostat (extremely hard to get to).

It has only cost $200 to do all of this. We figure it would cost at least a $1,000 in parts and labor at a shop and at least $1,500 if we had them also replace the thermostat.

After we get all of the parts back on it, we are going to use the water hose to try and wash out any stop-leak and/or gunk in the system.

Did I mention we only got two liters worth of coolant out of the ENTIRE cooling system? lol

Good luck!

I don't think you missed anything...good job, as a matter of fact!

I'd just check it every month or so and see if the sludge returns....

ITANSS, would NOT skip the thermostat. It sounds as if that was cocnuts problem to start with, but he replaced that along with the pump and so on. but that is somethig to NOT skip.

could have been thermastat and wornout rad cap also read somewhere as g.m. recommends distiiled water with dexcool not tap water. i guess they are trying to say that the tap water causes it to gunk up.

could have been thermastat and wornout rad cap also read somewhere as g.m. recommends distiiled water with dexcool not tap water. i guess they are trying to say that the tap water causes it to gunk up.
Coolant manufacturers have been recommending the use of distilled water since as far back as I can remember in the '70s. There are so many "unknowns" in our drinking supply (tap water)whether it comes from a municipal supply or well. Minerals are a big thing to consider in the water. Some areas of the country have a higher concentration than others which can wreak havoc on a cooling system. Before we got municipal water piped to my house in the early '90s, we relied on well water which was so hard you could barely use it to brew coffee, let alone wash clothes. Not a good thing to introduce into your vehicle's cooling system. Distilled water takes care of that and ensures a good base for mixing with the coolant.