Blown Neo head gasket - Next steps?

[Scott Black]

Leak down test helps determine what issues the engine has as when you do it if the pressure leaks out the manifolds then it's valves. Sump it's going to be rings or pistons, another cylinder or radiator then it's.going to be head gasket. As if your getting oil Contamination in the cooling system yet not showing up on a Tk or litmus test it points.more to the oil heat exchanger than the head gasket, an extended cooling system pressure test can also help narrow it down.
Although a big overheat normally does hurt the head a fair bit.

[Kinkstaah]

The worry is that the overheat initially can cause the head to warp as well. It would be worth mentioning that that had occurred to anyone you take the car to to ensure they check it because as mentioned, you don't want to replace head gasket then find out the problem is still there.

[V28VX37]

The worry is that the overheat initially can cause the head to warp as well. It would be worth mentioning that that had occurred to anyone you take the car to to ensure they check it because as mentioned, you don't want to replace head gasket then find out the problem is still there.

Totally - at a minimum they'll need to measure head and then skim if necessary.

I can just see this spiralling out quickly to the point that it's cheaper to just chuck in another Neo, however anything second hand is a gamble...

[Kinkstaah]

It is, but past experience in my case has shown that something built is an even bigger gamble!

[admS15]

After seeing the car on Saturday and what was happening and having a similar experience, my opinion is it is the h/g. As I said on the day if it was mine, seeing as the engine runs fine, doesn't blow smoke, makes good power and has decent compression.  Id be pulling it down, getting the head inspected and skimmed, replacing the gasket and studs and putting back together. As others have said though, you would feel foolish if you did all that and the problem still persisted. I think maybe a leak down test is probably the next best move to try and determine 100% the problem before you start spending money. I doubt its your radiator or hoses but if you want to rule them out, I have a known good factory rad and brand new rad hoses in my shed at home you can borrow for testing.  Its a bit of a tricky situation, maybe it's time for a professional diagnosis.

 

Edit. I would definitely stay away from replacement 2nd hand engine, especially since your engine is a pretty decent unit.

[V28VX37]

Thanks guys I will talk to the workshop and start with the leakdown.

In terms of rad this has been recommended but it's not exactly cheap: http://www.prospeedracing.com.au/products/mishimoto-nissan-skyline-r34-performance-aluminum-radiator.html

[WMDC35]

I've been using one of those radiators for about 5 years, no issues

[GTSBoy]

Just a word of caution with regard to "skimming" a head.  The head is more than just a surface that mates to the top of the block.  If the head has bent enough that the mating surface is no longer straight, then you have to wonder how straight the cam bearing tunnel is too.  These are not the same as old OHV heads where you could skim the crap out of them and just bolt them back on.

[V28VX37]

Just a word of caution with regard to "skimming" a head.  The head is more than just a surface that mates to the top of the block.  If the head has bent enough that the mating surface is no longer straight, then you have to wonder how straight the cam bearing tunnel is too.  These are not the same as old OHV heads where you could skim the crap out of them and just bolt them back on.

Thanks - I assume that would show up when the head is measured? Also if the head has gone banana would the same be true for the block? Can that be measured with the block in the car?

Bit of a headache (see what I did there)

[KiwiRS4T]

Block has a lot more mass. Clean it up  and stick a straight edge on it.

[GTSBoy]

1 hour ago, V28VX37 said:

 I assume that would show up when the head is measured?

 

Yes.  If measured carefully by someone who knows what they are doing.  To actually fix a warped OHC head, you really should heat it up and straighten the head by bending it back the other way....or whatever degree of clamping it down on a suitable surface is required to achieve it.  That way the mating surface and the cam tunnels both come good at the same time.

Edited October 3, 2016 by GTSBoy

[Scott Black]

Yeah to check block is straight after its cleaned for the new head to go on use a straight edge and ensure its dead flat,
As for cam tunnels.if you just getting the normal minimum done they generally won't check(surface grind and pressure test) yet if getting it serviced they will.
The block being a huge heap of cast iron will normally be fine unless it was a stupidly major overheat the alloy Blocks like sr20 are much easyer to warp. That's assuming your going to use an oem.gasket. If you wanted to use a mls gasket like cometic then the block surface won't be good enough.
It's a bit of a pain and expense do it it all properly yet it's better to do it right the first time than to cheap out and have.to.pay to.do it right later anyway.

[BlackBox]

In the process of re-installing the head on my neo after a leak at the valves, Had the head reco'd, ported and skimmed by Darren Lewis and im using a MLS gasket based on his advise. To prep the block i scrapped the old gasket material off with a razor, cleaned it with scouring pad and used 600 grit sandpaper on a flat black to sand on a 45 degree angle one way then the other so there was a cross hatch on the block. This was the way Darren Lewis recommended but having never done a head gasket let alone MLS i still have everything crossed that it wont leak.

[MrStabby]

20 hours ago, Dose Pipe Sutututu said:

because budget conscious track build and they're fine... ARP 2000 for big power and boost.

Since the head is coming off, might as well do value stem seals and also basic performance valve springs... RB25DET is prone to valve float once it gets some heat into it.. sometimes noticeable on the dyno after many pulls usually only noticed on the track.

Just checking - is float a problem with the neo solid setup @~300kw, or is that more an issue for the non-neo hydraulic at that power level?

[Scott Black]

There's a set finish that mls gaskets call for, if darren thinks that works then it may very well. Hes built some nice rbs over the years. And currently has my awd sump for some modification work

[admS15]

In the process of re-installing the head on my neo after a leak at the valves, Had the head reco'd, ported and skimmed by Darren Lewis and im using a MLS gasket based on his advise. To prep the block i scrapped the old gasket material off with a razor, cleaned it with scouring pad and used 600 grit sandpaper on a flat black to sand on a 45 degree angle one way then the other so there was a cross hatch on the block. This was the way Darren Lewis recommended but having never done a head gasket let alone MLS i still have everything crossed that it wont leak.

I have used this method on an sr20 and also coated the gasket with copper spray for good measure. I was sceptical about copper spray but a reputable and we'll respected mechanic/engine builder advised to use it, his words where that if it was a fresh build and the block had been machined he wouldn't but in the case of block still in car it was advisable and would seal any possible imperfections.

[V28VX37]

Thanks guys. I'm waiting for a quote from my workshop's engine builder, have also enquired from a couple of other places to see what people recommend.

Option A: Do to minimum to get it running properly then sell / Option B: Do it thoroughly and keep & hope nothing else breaks soon (unlikely). Kinda over spending 20x more time building than driving the thing at the moment...

Edit: Scanning eBay, there's a 'Nissan Skyline RB25DET Neo Engine R34 - Long Motor fresh top end rebuild' listed for $1,750 ... tempting.

[admS15]

Fix yours on the cheap and drive it till it won't drive no more. Probably a long time away.

[Dose Pipe Sutututu]

2 hours ago, MrStabby said:

Just checking - is float a problem with the neo solid setup @~300kw, or is that more an issue for the non-neo hydraulic at that power level?

Shit forgot it's a R34, I keep thinking he has a R33 boat like most of us.

 

Please ignore what I said previously, just stick to the ARP studs lol.

[BlackBox]

I have used this method on an sr20 and also coated the gasket with copper spray for good measure. I was sceptical about copper spray but a reputable and we'll respected mechanic/engine builder advised to use it, his words where that if it was a fresh build and the block had been machined he wouldn't but in the case of block still in car it was advisable and would seal any possible imperfections.

Yep darren Lewis did say to spray it with hylomar as well