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troopie
06-07-2016, 06:06
Does any one know what a reasonable internal engine coolant temperature should be?

I have a factory Toyota gauge (ungraduated) in the front of the left hand head that never gets over half (I've had the gauge tested, it works fine) that lulls me into a false sense of security.

I also have a VDO mechanical gauge in the rear of the right hand head that scares the bejesus out of me!

On a hot day (that's every day when the sun's up where I live) it's often sitting at 90c (193.9F).

When I'm idling it will creep up near 110C (211.9F) if I let it (I try not to, I generally give it some herbs at traffic lights etc. to get the water and air flowing). I have no fan shroud yet; please don't judge me on this :o It was supposed to be made this week but has been delayed. :( This is a temporary problem hopefully to be rectified soon. My bigger concern is the figures in the previous paragraph.

Are these figures reasonable or bad. I'm worried I'm slowly cooking the poor old girl before I've even got the conversion finished. I've no idea what a good temp should be but to me water boils at 100C so it seems high. Yeah I know it wont boil 'cause it's pressurised but what's the healthy upper limit?

Now I know the old 6.5's were known for getting a bit hot at the back of the heads; does this explain the discrepancy? Does a healthy temp measured at the front of a head near the pump mean you are always going to get a higher reading at he back? If so how high can it safely go?

I also have a plan to plumb the rear water ports of the heads to the thermostat housing but that's another topic.:)

Robyn
06-07-2016, 08:19
193 F is not to worry about.

What stats are you using ???

I like 180 F to get the coolant flowing a tad sooner.

Seeing 210 F under hard pull is not uncommon, but keeping it down in the 190 F is just fine.

Once you get the shroud in there and the fan pulling good air flow it should be fine.

The rear of the engine is always going to be hotter.

Factor piston to cyl wall clearance is spec'd out at .0005" more for the rear 2 holes.

I like .0045" in the back and .004" in the other 6 holes.

No worries mate, you are right in the 6.5 groove.

Just get the air moving good and you will be fine


Just an FYI

Forget the plumbing on the rear ports.

The coolant is supposed to flow to the rear of the block, then travel up into the heads then back forward and out through the stats.

The early 6.5 heads had some areas that got hot due to low coolant flow (Stagnation) and this issue was fixed in the AMG engines.

Short circuiting the water flow actually can do more harm than good.

troopie
06-07-2016, 13:31
Thanks for setting my mind at ease Robyn. :)

I've got the dual 'stat housing, no idea what temp the 'stats themselves are though.

Thanks for the heads up on the rear ports too. That was something I was gunna ask before I plumbed 'em.

So at what temp would you consider your donk to be overheating? It would be good to have an upper limit to keep in mind.