[Gwagensteve]

This is just a little idea I've had whilst working on Piggles.

More specifically, we all know G16B's crack heads/do gaskets. The seem to do this more readily when installed into Sierras, and it's not always connected to overheating.

We also know, anecdotally, that Baleno G16B's seem to have a very much lower rate of cracks.

Jono165 has proposed that this is because the coolant flow in the head of the Baleno is front to back (from water pump to back of the head) but on the Vitara it's front to back and then back to the front again, increasing the chance of hot spots and steam pockets.

However, I've noticed that one of the heater hoses on the G16B (vitara) flows out of the back of the head, where the top radiator hose is on the Baleno.

IIRC, the Vitara has constant flow through the heater core - there's no tap, air is blended through the core or not as required. that means there's constant flow through the back of the head of the G16B when it's in a Vitara.

If you install a G16B into a Sierra and plumb the heater hoses as per a G13, the flow from the back of the head will stop at the heater tap when the heater is off.

I wonder whether this contributes at all to the rate of head cracks in G16B swapped sierras?

I wonder whether the jimny has a heater tap or constant flow through the core like a Vitara?

Is this something everybody has missed with G16B swaps?

Steve.

[greenzook89]

Can confirm Jimnys don't have a heater tap.

[alien]

Wow, that's really interesting!!

This said, If i run my heater tap open in the sierra it COOKS inside due to the general airflow from the bonnet vents. In summer I have used the heater while crawling offroad to lower the engine temp though.

I wonder if there's a way to plumb the tap to just bypass the heater core but still flow through the back permanently? Probably create some sort of reliability issue though?

[Gwagensteve]

Cheers greenzook.

I do think I'm onto something here then - It appears that any car with the 16V SOHC head has continuous flow at the back of the head - hot coolant can escape the head, either due to the transverse setup or through the heater core.

Alien - yes, I reckon looping the outlet from the back to the head back into the inlet side of the water pump (where the factory heater hose returns) would be best. Whether running a couple of tees and running the heater off of that loop provides any heat in the cab, I don't know. I think the reliability issue would be a small thing - it's just some more hose clamps and some generic tees.

I'm certainly going to recommend completing the loop with continuous flow to the guys I know running G13BB's/G16B's.

[bumstein]

Intriguing!

Righto trying to get my head around this.

Below pic of Sierra water hoses, if I’m right the flow of water is something like this:

Bottom hose of the radiator,
Water manifold,
Water pump,
Water jacket in the block,
Pumped up into the head,
Through to the inlet manifold.

From this point it goes one of three directions,

1) Heater tap, heater core then drains back to the water manifold.
2) if the thermostat is closed it drains from the small hose at the bottom of the inlet manifold back to the water manifold.
3) through the thermostat, through radiator and back to the bottom radiator hose.



Is that correct? Once I’ve got that I can look at how the other motors are done

[Gwagensteve]

Yes, I think you have it.

Water for the heater is drawn (I'd rather describe it as drawn because there's suction in the water manifold) from the inlet manifold, past the heater tap, through the heater, and back into the manifold.

So from item 20 and back into the manifold via item 23.

What's critical about this is that the whether water flows through the heater or not makes no difference to what's happening in the head - coolant has already flowed through the head at this point and is now flowing into the inlet manifold galleries. Whether some of that coolant is diverted to the heater core or all goes to the thermostat housing isn't very important.

But in the vitara the water flows out the back of the head at all times, through the heater core (As there's no tap) and then back into the water manifold.

However, just thinking about it, the Jimny must have a different flow path because even though theres no heater tap, the port on the back of the head is blanked in Jimny's - it's just tinplate. That makes we wonder if the Jimny inlet manifold pulls coolant off the back of the head to the heater.

Steve.

[Gwagensteve]

Hmm, Im interested in the G13BB jimny (not that they are immune from killing heads) but It's a bit hard to figure out.

I have this image:



but I can't work out where the hot coolant running to the heater core attaches to the engine. (return is basically the same as a Sierra/Vitara)

Does the hose #14 connect up to under the thermostat housing somewhere?

[bumstein]

From the throttle body I think. Flow must pass through the head, into the intake manifold then back to the water manifold or the heater core then back to the water manifold



Hmm.. I’m not sure that makes sense.. I’ll have another look

[Gwagensteve]

No, I don’t think that’s it.

[bumstein]

Nah definately not. The hose 11 goes to the intake manifold on the right (drivers) side, can’t see that outlet in this pic. I reckon there will be another outlet at that spot heading to the heater pipes

[Gwagensteve]

Interesting. That means the Jimny has the same coolant flow as a Vitara with the rear hose blocked off. I know Jimny's aren't great in regard to heads, but they also run less stroke (piston at TDC for less time) and less power and torque, they're also lighter than a Vitara and run shorter gearing, so I wonder if that takes enough thermal load off the head the Suzuki didn't see the need to worry about it?

[sideways]

Timely thread, as I'm faced with a Sierra G16b conversion I've been looking into this quite heavily over the last couple of weeks.

Gwagensteve wrote:

Vitara it's front to back and then back to the front again

I think this is a big part of it though, does the coolant actually get to the back? The headgasket has biggger holes at the back and smaller holes at the front to promote flow to the back of the block. Is it enough?

Water comes in the drivers side of the block, the head gasket has small holes for coolant on the drivers side so coolant is promoted to flow to the passengers side of the block, then up through the deck into the passengers side of the head and across to the drivers side and out the manifold.

The heads crack right down the middle end to end which suggests a difference from side to side. Perhaps as the vitara exhausts its water on the drivers side we're getting to much flow through the drivers side of the deck and the hotter exhaust/passengers side of the head is getting insufficient cooling.

I found different part numbers for G16b head gaskets but I couldn't find pictures of the genuine gaskets to see the difference. I wonder if there's different configurations of coolant holes.

There are 4 port heater taps that divert coolant flow instead of shutting it off. Still I think this is messy, you're going to be diverting uncooled water back into the water pump and I feel the Sierra cooling system is a bit marginal to cope with that for my use. You could plumb it back to the bottom of the thermostat housing but then how can you ensure flow? EWP? Plus, combining different temperatures of water so close to the head doesn't really sound like the best thing to be doing. I don't think there's a clean solution here.

Maybe the solution for the Vitara motor is to take the coolant from the back of the motor like we would in a Baleno conversion and block off the thermostat on the manifold. I've been considering doing this for mine, though it would be almost impossible to know if this was successful or not.

I think we can say that it's primarily the Vitara that suffers from this. It happens to Jimnys but it's rare and they can see a much higher load at slower speed (eg sand on a hot day) than a Baleno ever will. We've heard of a couple of cracked heads on Bals now but it still is rare. Swifts and 1.6 GVs are too rare to comment on.

Interestingly the latest vehicle with the G16b, the APV van doesn't appear to have any coolant flow out the back of the head. I've never heard of a cracked head on one but then it's not likely we'd hear about that anyway.

[Blkfxx]

Baleno water flow for reference

[Gwagensteve]

I wonder what the "breather pipe" is, and what market/configuration it's applied to?

Anyway, here's the same diagram from the G16B Vitara. It confirms my theory about constant flow out the back of the head.

[Gwagensteve]

I was just talking to my wife about this and staring at that image from the Vitara FSM.

Yikes - what happens if there's no flow out the back of the head (heater tap shut) and the thermostat opens? - there's only convection flow at the back of the head. :kettle emoji:

[sideways]

Gwagensteve wrote:

Yikes - what happens if there's no flow out the back of the head (heater tap shut) and the thermostat opens? - there's only convection flow at the back of the head. :kettle emoji:

Nope.

Quote:

The headgasket has biggger holes at the back and smaller holes at the front to promote flow to the back of the block.

I think I'm going to plumb mine conventionally but I'll tap the outlet at the back of the head for a temp sender. If it's hot there I'll install a bypass heater tap.

[Gwagensteve]

I understand your point, but that's not a circuit, it's still relying on convection rather than pressure differential.

The problem is the head. so the coolant is being pushed into the block at the front. It's escaping at the front of the block too. with constant flow at the back of the head, there's a circuit with constant suction at the back of the head, even when the thermostat is shut - so there's continuous flow.

Shutting that off is dead-heading the back of the head. I agree at high rpm (>3k or something) there's probably enough flow that the holes in the front of the head gasket present enough restriction that there's flow at the back of the head regardless of the heater configuration, but I'm not at all sure thats the case at low revs and it definitely won't be the case with the thermostat shut.

The problem seems to be, as you pointed out, different thermal expansion across the head, and I think preventing flow to the back to head, as designed by Suzuki, would be a very logical culprit.

[bumstein]

Swift GTI cooling system



Ok so forgive my ignorance in this regard, when you slide the temperature knob to ‘cold’ on a Sierra, the heater tap shuts preventing the warm coolant from circulating in the heater core. Do other vehicles not shut that heater core down in the same manner?

[missmyljdaze]

I have had several vehicles where the coolant was always flowing through the heater core - acting much like a secondary radiator.

Switching from hot to cold only altered the direction of air flow - either into the cabin or in the general direction of outside.

V6 Capri was a good example, if the heater core was blocked or bypassed, you were verging on overheating as the radiator was barely able to dissipate the heat by itself.

Same as Aron - if you were stuck in traffic, you could swivel the dashboard's outboard "eyeball" sockets so they were directing hot air flow out the windows and prevent boiling.

At least one [maybe more] of my fiats either had no tap, the hot air being directed either into the cabin, or outside via the vents in front of the windscreen.
One of my 125s fiats had an air duct dumping hot air downwards and underneath the floor.
Cant be certain if these were factory original, a dealership modification to help cope with the W.A. wheatbelt being generally a bit hotter than Italy, or done by my mechanic who knew lots of tricks to help fiats survive longer than intended by the manufacturer.

[bumstein]

missmyljdaze wrote:

I have had several vehicles where the coolant was always flowing through the heater core - acting much like a secondary radiator.

This being the case (and presumably it is) perhaps a three way tap might be more appropriate? If one were to shut the flow to the heater core it would then flow through a bypass or alternative cooling core. Just a thought.

I was trying to find a similar diagram in the Sierra FSM but didn’t find one in my sleepy state last night.

[bumstein]

What’s people’s thoughts? I was thinking something like this;

https://www.onlineautoparts.com.au/prod ... /ZPN-01366

[Gwagensteve]

That looks like a good solution and neater than the suzuki tap too.

[bumstein]

Be interesting to see if it solves the head cracking issues. Might give it a try

[Gwagensteve]

It absolutely can't hurt

[alien]

Interested to see what the holden one looks like installed!

[bumstein]

Haven’t thought too hard about that yet. When I start putting one back together (a couple months hopefully) I’ll report back

[bob_oz]

from an alternate angle,

HK holdens use a shut-off-tap on the inline heater, HT's and HG's dont, they let water flow through all the time, HQ's-WB's have a three-way tap to reduce cabin temp..
HT's and HG's run far cooler and are more stable.
I deleted the heater on my HT when I fitted triple delorto's and hey presto i'm overheating and having weird temp increases/decreases like all my HK's

I think you are onto something -

Try either plumbing it on 100% of the time and see if that helps - otherwise those 3 way taps are ok