Incompatible coolant?
 

When I bought my car it had the nasty green coolant in it. I recently flushed the system and refilled with Zerex G05. The basic process I used is as follows:

1. Drain old coolant from radiator petcock
2. Drain from block
3. Remove thermostat and install housing without thermostat
4. Refill with system with water; bring to operating temp with heater on full
5. Let cool; drain system
6. Refill with Prestone flush; bring to operating temp with heater on full
7. Let cool; drain system
8. Refill with water; bring to operating temp with heater on full
9. Let cool; drain system
10. Refill with water; bring to operating temp with heater on full
11. Let cool; drain system
12. Install thermostat
13. Refill with Zerex

After a few days I noticed that the nice new amber coolant I had just put in now has a slight green tint. Before I replaced the thermostat, expansion tank cap, refilled the fan clutch and flushed the coolant with temperatures around 100F my car had been getting up to 100C (mostly in stop and go traffic). Afterwards it stays pretty consistent around 85-90 in traffic but now going 80mph on the highway or up hills at 85F the temp will climb to 95-100C (no AC). Could the slight bit of green coolant apparent in the system be reacting with the new coolant and causing this problem?

I'm thinking about draining and heavily backflushing this weekend but I wanted to get some insight if there is something else I should look for?

How did you refill with the Zerex, through the overflow tank?

You may have air trapped in the system.

I slowly refilled through the expansion tank with the car up on ramps. I also ran the system without the cap and burped it several times. I haven't experienced any major changes in coolant level and the overheating is a much more gradual than sudden (I've read air pockets with cause sudden temperature surges).

You forgot to turn on the heat. Best way to do it is to flush it all out. Drive it. Flush again. Drive it. Flush again. Water is better than coolant for dissipating heat, but freezes and boils quicker. The system is self purging, should be no need to "burp". Year and model in your sig or userCP with worth a thousand words.

"Refill with water; bring to operating temp with heater on full"

Sorry about no vehicle info I agree that is annoying ... I could have sworn I entered it in when I first set up the account.

1995 E300D

My bad. Eyes are a lil fuzzy at the end of the day. Still. It takes alot of flushing to get rid of it all (if its truly even possible). The coolants are not incompatible the green stuff is incompatible with the engine. Drive it for a bit, flush, drive, flushd drive and flush again. What I mean by drive is like a day or 2. As long as its not with AC on and 100+ heat (again location in sig or CP) you will be OK. We ran in 90+ heat at WOT for 15hrs with water in the radiator.

Thanks, I guess I will drain all of the new (befuddled) coolant out and refill it with water for a couple days and run it. This time I also think I will flush through the head and out the block more thoroughly.

I had heard that mixing incompatible coolants can actually cause the mix to gel or become incredibly acidic which can lead to a blocked radiator and/or less efficient cooling system.

The green stuff is already acidic. For a proper flush you are supposed to remove the block heater plug on the engine. One of the plugs, maybe not block heater. Read FSM on citric flush if you are going to go to all the effort.

And maybe update your car and location?

When I flushed mine to switch from the green coolant, I noticed that it had petrified in places (like inside the thermostat cover). I flushed with water a bunch of times till it came out clean, then did the acid flush and it came out significantly green. It appeared to have dissolved a lot of the petrified green coolant as evidenced by a lack of green inside the thermostat cover afterwards. Maybe that's what's going on with yours.

Perhaps Prestone formulated their flush specifically not to dissolve the petrified coolant so it wouldn't get a reputation for causing systems to start leaking afterwards.

<edit> Yes, do flush it again, but I wouldn't run it with straight water for a few days. I'd use a low percentage of antifreeze to provide corrosion protection to the metal inside the engine.

Thanks for the replies. I will flush it again this weekend.

I'm somewhat confused. What are you hoping to accomplish by flushing it again? Are you wanting to remove the vestiges of green or address the temperature issue?

This is NOT true of mixing the green stuff and Zerex G-05. I was concerned about this too when I was making the switch so I talked to several folks at Valvoline about the issue. I was told the the incompatibility that results in the gelling is between the green stuff and Dexcool.

At any rate, the folks at Valvoline tech support are extremely helpful....might be worth a phone call.

yea i really kinda need to do that flush.

Dexcool is just a nightmare all around. My wife had a '99 Malibu with that stuff and it would form hardened stalactites inside the coolant reservoir. I've never seen anything like it. Eventually the car died of a blown head gasket. Good riddance to bad rubbish.