Flushing Coolant System that is clogged?

Hey All,

I recently purchased an 06 Tundra with a blown headgasket. Today I was draining the coolant before beginning to tear down the top of the engine. I had read a post about flushing the block by blowing compressed air into the coolant hoses that connect to the heater controller. This worked well. A half gallon of coolant came out of the radiator drain hole. Then it turned to sludge, and the system clogged. (The sludge is likely the culprit of the headgasket failure/overheating, due to a clogged water pump).

Anyways my question is this, should I try to unclog the cooling system before or after tearing down the engine to fix the heads? How should I go about flushing the cooling system? I would try to connect a hose to it and just push water through, but it is getting below freezing at night and I am working outside. The engine barley runs so trying to doing it running isn't really an option.

 

Sounds like the PO probably had an overheating problem, cooked the head gasket, tried to fix it with some "As Seen on TV" gunk, and totally screwed everything up in the process. Since you're tearing it down, you should probably replace the radiator and the water pump. You're going to have most of the engine apart anyway, so you might as well do the timing belt with the water pump. I'm kind of at a loss as to how to flush it. I'm sure someone with more knowledge on this will chime in. Stay tuned.

 

Hey @ATBAV8 yep the PO sold it to me because it had overheated and the headgasket blew (which I confirmed today with a compression test). She had a major service 500 mi before it overheated including the timing belt, radiator, and heater core flush. Im guessing some radiator stop leak gunk was used before she took it to the shop and the shop didn't flush it well. Before I found the gunk today I had wonder if the shop may have messed up the timing causing all the issues. Im trying to decide if I will do the timing again as well (even though it was done 500 miles ago), but its relatively cheap for peace of mind. I'm definitely planning on replacing the water pump, radiator, and thermostat.

 

You're already in there. Might as well. At least then you would have peace of mind knowing it was done correctly. Be sure to install the AISIN kit. Get it at Rock Auto.

 

You're in for a treat on this one, with VVTi. I'd be tempted to replace the engine with a good used. But if you're in for an adventure I guess you've got it

 

I'd use a garden hose. One of these cheap nozzles makes a perfect adapter to heater hoses. (use the clamp on the heat hose)

I'd start with the heater core. Remove the heater hoses from the engine side, connect the garden hose and flush it and back flush it with lots of water -- until it runs perfectly clean. Don't worry about running the discharge out onto the ground -- you've removed 95+% of the coolant by draining it and blowing it out with compressed air. Any trace amount that's left will be sufficiently diluted with the gallons and gallons of water you're going to use to flush. When you're done flushing, blow the heater core out with compressed air. Since you're concerned about cold temps, dump a little fresh coolant into the heater core -- that will protect it from freezing.
Then reconnect the heater hoses to the engine, disconnect them from the heater core, and flush/back flush the engine. When it flows clean, blow it out with compressed air, dump a little coolant in, and begin your head gasket job.

 

Kimmy asked me to weigh in on this...

I don't have any direct experience with clogged cooling passages, but one of our members @Tundra2 has. Hopefully he'll pop up now that I've summoned him to post the link to his thread. However, his engine was intact and running, making the process seem somewhat more manageable compared to your situation. In theory you can probably use a combination of air and water pressure to clear the waterways of much of the schmootz, but in practice it may be difficult to get it all. After you get the engine back together you can continue with flushing and sacrificial fill/replace treatments until you're happy.

My concern for your situation is that when a head gasket blows due to overheating, there's a potential that the head(s) may have warped. Once you get the heads off be sure to get them to a machine shop to assure that they're flat before you invest time/money. As others have pointed out pulling/replacing the heads is not minor surgery. If you pay someone to do it the cost of an engine swap will suddenly seem reasonable...If you do it yourself you'll use up all your free time for many weeks.

 

Thanks @shifty` working in freezeing temps definitely complicates things. What about the VVTi makes it harder? What kind of pitfalls are there trying to repair an engine in this state? Thanks!

 

@tvpierce Thanks for the advice! Do I need to remove the thermostat when I backflush the engine? I was more or less attempting to do what you suggest but with compressed air when it seemed to clog up. I was blowing it into the coolant hoses coming off the back of the engine. I'll try with water, but if it is still clogged I'm wondering where it could be constricting. Thanks!

 

All the extra shit, both on the top end (stuff for variable valve timing), the SAIS pump, valves on the back of the block, and solenoids over bank 2 that power those, who knows what else, but it’s definitely a different, more complicated beast than the pre-2005, non-VVTi iterations.

Make sure you follow process on everything, the 2UZ isn’t like working on a SBC where shit would be straightforward. You can put it all together, but miss a step, and have the engine eat shit 2k-3k miles later, which one guy who bought his truck used, from a Toyo mech who did something, missed an obscure step (I think with the valves, memory is fuzzy). Getting timing right with the cams first, then with the actual timing is a chore. Get a copy of the FSM which is downloadable from links at the top of the sticky thread “So you just bought a 1st gen…?” and you should be alright.

 

@w666 Thanks for this. Yes definitely planning to take the heads to a machine shop and replace the radiator/waterpump/timing b. Getting all the schmootz out seems a bit tricky. I guess I'm just concerned about getting it back together and getting some junk stuck somewhere again (like the water pump). I'm wondering where the smallest passage in the cooling system is (once the thermostat is out) and if water can freely flow through the waterpump with the engine off?

 

Oh and don’t forget, VVTi, and all. If you have the heads milled because they warped or are out of spec, any change in head or deck height may fuck with VVTi, to to change in distance from crank to cam, even if only by thousandths, you never know… and I don’t know if Toyota makes a thicker head gasket to compensate for exactly that. I’d consider buying two good used heads myself, if something is warped.

 

@shifty` the kind of thoughts that make chills run down my spine. Will have to research VVTi and milling heads.

 

Question- Have you scoped the cylinders to check that the pistons and bores look good? I know 2UZs aren't known for cylinder wear but I wouldn't want to spent hours tearing it apart to realize it needs an engine. Not the same thing- but I overheated a boat engine once so badly that the pistons expanded and wrecked the cylinder walls. I don't know. Just something I thought of.

Side note- it looks like you can buy reman'd cylinder heads for $1200-1600/pair. Makes me wonder if that would be more cost effective than tearing down the heads yourself and finding a machine shop to trust.

 

@FiatRunner I havent scoped the cylinders yet. I should do that before I proceed any further. Will have to find a borescope to borrow. At that price maybe better to put in a new engine if I can find one in the 2-3k range.

 

If I remember correctly an entire junkyard engine costs $800-$1200ish, some with great miles when I checked for fun a few months ago.

 

Found you an engine in ABQ...call them:

http://recycler.car-part.com/MMBodyLLC/

 

They are pretty cheap these days on Amazon. I've got one that just hooks to my phone and they're even cheaper that way.

 

Thermostat in. Upper and lower radiator hoses disconnected from the radiator.

 

Thanks @w666 I gave them a call!

 

last year when i had both my water pump and thermostat housing removed i blasted the block out with a pressure washer.

 

If you are doing a tear-down, run pure white vinegar through the cooling system. White vinegar will remove everything.

 

Just a thought but these are made to unclog drain pipes. They swell up to fill any gaps and shoot pressurized water down it's gullet.

 

those do work good on drains, not sure automotive application,

 

from what Ive read I would go with a used engine . Ive delt wiht rigs that had been cooked and most did not go as planned/hopped. I did some research before buying my 2002, and did not want to mess with the vvti engine

 

Have to be careful with the pressure.

 

That may work, but it's unnecessary. I have a couple of those in different sizes -- they work miracles on drain pipes. On a vehicle, the cheap brass garden hose nozzle I indicated above gives a perfect seal on heater hoses.