3VZ strange overheating issue just

[smash]

So I'm going to Spa next week and I want to take the Ferota but it's really trying it's best not to go!

Today it's decided to develop a couple of new faults - this one revealed itself in traffic queue.

Stationary in queue temp gauge rose steadily to 3/4 at which point I panicked and opened heater matrix, stuck heater fan on and rev'd engine to about 2k

Within a couple of seconds the temp gauge suddenly plummeted to normal. Same thing happened again after I'd turned the heater fan off - but reving the engine gave the almost instant temperature drop again. Normal running temp for the car is somewhere just under halfway. temp stays down when on the move

Haven't started fault finding yet but would appreciate any suggestions for likely culprits!

[cdwood2010]

Panic not, this is a known issue.

A pattern water pump doesnt move enough water around at tickover, but its fine when running at a higher rev.

The Totty one seems to work just fine. Any idea what water pump youre using?

Chris.

[smash]

Ah OK - thanks for prompt response btw! The pump should be whatever was fitted by Woodsport at time of conversion - weird it has never done this before though.

[cdwood2010]

Yes I think Paul discovered this by comparing swaps. Something to do with the number of fins on a water pump.

If you rev the engine occasionally it should shift the water around enough to keep things normal.

Paul should be able to confirm what water pump would have been fitted, just in case I'm talking plop!

C.

[cdwood2010]

Oh and here's the original thread about it....

V6-water-pump-discovery!
http://www.twobrutal.co.uk/forum/showthread.php?t=15423

[smash]

Ah-ha! So I have an 'orrible Quetin pumping water round me lump!!

Yep the symptoms on that thread are exactly what is going on - I guess it's the first time I've been stuck in traffic (there was an accident so stationary for a long time) on a reasonably hot day. Well it can get hot under the collar all it wants - it's not getting a new pump before Spa!

[cdwood2010]

I wouldn't sweat it (see what I did there?)

If (god forbid) you get stuck in traffic, turn your engine off.

Simples.

:)

[aussiemr2]

I have been having the same problem but I certainly have a genuine Toyota pump in mine
Turns out I have a massive airlock as you can hear it gurgle after turning engine off

[briweekes]

Appreciate this is an old thread. Thrillseeker discovered a common issue with the top hose running from the rad cap, over the top of the engine and forwards from there. Air accumulates at the top curve of this pipe. Cutting and fitting a small alloy tube with a vent hole at the top (bolt hole), allows air to be vented out. Works a treat. I had the same issue, fixed today.

http://www.twobrutal.co.uk/forum/images/recovered/2015/04/169.jpg (http://s1358.photobucket.com/user/coffeebarman/media/colling%20system%20air%20vent_zpskiio5ihc.jpg.html )

[Paul Woods]

On 200+ V6 swaps i've never seen this issue, the filler point is the highest coolant point in the engine bay, so all air rises to that point and gets purged to the expansion bottle during cooldowns.

If you're seeing air trapped in the pipe coming from the filler point then it must have a funny angle on it making it the highest point for the air to get trapped.

Air will always find the highest point, and can be confirmed by unscrewing the pressure cap on a cold engine, there should always be coolant visible, furthermore having a very small pocket of trapped air in a small section of pipe on top of the engine is definitely not going to cause an overheating issue, it just won't, there must be another problem lurking or cooling system issue.

I'm all for fixes and cures, but you have a factory bleed point less than 6" away from that one.... so i would be looking elsewhere if you're having issues.

[briweekes]

No other cooling issues, it was just not efficient with the pipe going over the top of the engine and a high point there. Coolant circulation seems better now. No funny angle. This was tested. By thrillseeker using transparent marine hose, which revealed air accumulating at the top of that arc, and not being able to be bled out.

[Paul Woods]

Then the pipe had the wrong angle on it which made it higher than the filler point, if the filler is the highest point then you don't need any extra bleed points.

[cdwood2010]

Looking at most 3vz builds (and mine) people use either a regular aftermarket hose or the original Camry top hose. It has a habit of sitting a bit hunched.

I've noticed Paul uses a slightly different hose with a lower profile so this isn't an issue.

I generally fill up the coolant with a pop bottle hopper - basically a pop bottle made into a funnel with the top thread wrapped in masking tape so that it seals. That way you can give the top hose a bloody good squeeze and get all the air out, then cap on. Never had an issue once its bled fully, but I have seen air trapped as Brian describes.

[Paul Woods]

I guess my point is even if you had that top hose with a small airlock in it, that isn't going to matter and will eventually be forced out, the filler neck is still the highest point in the bay and air will always find its way there.

Mr2 cooling systems are self topping up once you have the inital burping done, the pressure cap acts like a tidal gate.

When running it should never open unless there is a problem.
On shutdown the pressure builds in the engine and the cap opens forcing coolant into the expansion bottle.
When cool the engine now creates a vacuum, which sucks coolant back out of the bottle back into the engine via the cap which allows return under those conditions.

So all trapped air will eventually find its way to the bottle.

Extra bleed points are simply not needed.

[cdwood2010]

Um, I always thought the expansion bottle was just for expansion, didn't think it could draw coolant back through a one way valve.

I generally just bleed them lots and leave the hopper full overnight. It gravity eventually gurgles it into the system.

[Paul Woods]

The coolant pressure cap is a two way street, it flows both ways, out under pressure, in under vacuum.

[cdwood2010]

http://www.twobrutal.co.uk/forum/images/recovered/2015/04/2.gif

[Paul Woods]

If you notice the pipe leading from filler point to expansion cap it goes to the tube that is submerged in the bottle, so it is never allowed to suck air back in, only coolant, so the system works like the tide flowing to and from the bottle on shutdowns.

People see problems from piping to the wrong outlet of the expansion cap, using the overflow as the feed, so what happens is the engine chucks coolant out on shutdown but during the cooldown period draws air back in, this gives an almost head gasket failed symptom, same thing happens on Mk1s with the original white plastic caps that crack, although plumbed properly it draws air back in during cooldown. The later Mk2 black plastic caps do not crack and never see the issue.

But yes, essentially extra bleeds, although not doing any harm, are not needed on V6 swaps.

[cdwood2010]

okay, I still don't understand how a pressurised cap, requiring 0.9 bar or whatever to open, can open and suck coolant back in.

The pipe to the expansion bottle sits above the spring cap seal, so certainly pressure (>0.9 bar for example) makes it open and expand, but how does it open to draw coolant back in again?

http://www.itdec.eu/images/I-do-not-hunderstand.gif

[Paul Woods]

It's witchcraft, and i've no clue what i'm talking about.

http://auto.howstuffworks.com/cooling-system7.htm

[cdwood2010]

Oh that I get, but the MR2 doesn't have a route back. The expansion bottle is like one of those wee bottles they give you in hospital.

[Paul Woods]

Seriously chris just trust me mate, the cap flows both ways.

[cdwood2010]

Fairy nuff, wasn't saying you made it up, I seriously didn't know it could do that.

[Paul Woods]

If it didn't have a route back your engine would gradually dump all of its coolant into the bottle which would overflow very quickly, think about it.

The pressure cap is bi - directional, trust me.

[cdwood2010]

Oky doky.

But last time I trusted you I woke up in a dress with a sore bum.

:)

[Paul Woods]

That's cos you're bi - directional too.

[cdwood2010]

Well bugger me. (no not you). I just had a go at a rad cap with a small screwdriver. There's a small hole in the centre of the pin, and the central cap bit on the bottom has a secondary spring allowing it to open..

I really fucking hate you, you smug know-all bastard.

http://www.millioncarparts.com/images/products/engineparts/g101051074fut.jpg

[Paul Woods]

My work here is done.