V8 Head Gasket Thoughts...

[Aragorn]

I've pulled the passenger side head from my P38 (1994 GEMS 4.6) (drivers ones proving to be annoying!) but i'm curious about some of the findings.

The engine was pressurising the cooling system, slightly, and using coolant, but drove fine and you could do 100's of miles in it a day without issue. Lots of short trips seemed to guzzle coolant, but a long trip would only use a little, suggesting it was leaking more when cold perhaps?

Spark plugs on 1 and 3 would turn orange over time. Its been like this for several years and i've finally decided to fix it as it seems to (finally!) be getting worse with some signs of water on the other bank.

I'm particularly curious having removing the head though, of how exactly its ended up the way it has.

Examining the head and pistons, you can see that 1, 3 and 7 all appear to have signs of steam cleaning, with the clean areas of the piston crowns and clean areas of the head. 5 looks pretty normal.

Moving over to the gasket, cylinder 1 has obvious rust on the firing ring, so we can imagine thats certainly a path between the water jacket and cyl 1. Oddly enough for the cylinder with the most obvious water route, its the dirtiest of the three cylinders. Cyl3 has a small amount of rust on the fire ring too. I guess i'm pondering how water got into these cylinders in the first place to rust the fire ring though... Especially 3, it doesnt appear to be near any water... Cyl 7 fire ring looks fine, infact theres nothing obvious at all around cyl 7, so not sure why its showing signs of steam cleaning. It is ofcourse adjacent to the water jacket, so it certainly could be leaking across from there.

Is there anything else i can check while its apart? Cylinder liners being the obvious question mark.

Ive put a stream of photos on imgur: https://imgur.com/a/PyyyvxJ

Edited August 1 by Aragorn

[smallfry]

Looking at the first picture, at the edge of the liners adjacent to the head bolt holes, you can see marking that is the classic sign of liner leaks.

When the engine is stopped, the cooling system is still pressurised, forcing a small amount of water vapour into the cylinder, which will then condense as the engine cools, and sits there until the engine is started again, which is why rust can form.

Its fairly obvious that it is the strain of the head bolts that distort the block that causes this, Likely because the bigger bores have weakened the block casting in this area. Would doing up the head bolts less tight have helped ? Who knows. Lots of people have used studs and even more torque to tighten the heads down, but I cant help wondering if this only makes it worse.

Best solution would be to fit a 3.5   

[FridgeFreezer]

I had a sort-of-similar thing with the Ambulance - it could run for 100's of miles no problem but the coolant would eventually drop and it would overheat, I didn't have any evidence of where it was going (no rust etc.) but ended up doing the gaskets and fitting head studs which cured it, and consensus seemed to be it was a very small weep through one of the gaskets - thread here with photos if you want to compare notes:

 

[Aragorn]

13 hours ago, smallfry said:

Looking at the first picture, at the edge of the liners adjacent to the head bolt holes, you can see marking that is the classic sign of liner leaks.

When the engine is stopped, the cooling system is still pressurised, forcing a small amount of water vapour into the cylinder, which will then condense as the engine cools, and sits there until the engine is started again, which is why rust can form.

Its fairly obvious that it is the strain of the head bolts that distort the block that causes this, Likely because the bigger bores have weakened the block casting in this area. Would doing up the head bolts less tight have helped ? Who knows. Lots of people have used studs and even more torque to tighten the heads down, but I cant help wondering if this only makes it worse.

Best solution would be to fit a 3.5   

Do you mean these?

Would certainly explain why cyl 3 has water in it!

 

[smallfry]

Yes those, and the same on the cylinder to the left to a lesser extent.

Another thought I had, was that although the composite gaskets are supposed to seal the waterways better, the fact that they must "give" a little when the head is tightened down might allow the head itself to be distorted slightly, and also allow the block face around the bolt holes to be pulled up.

This never used to be a problem on the 3.5 engines that had steel shim gaskets. Although the accepted wisdom with the early 14 bolt heads was that the extra row of bolts "tipped" the head, and allowed combustion products into the crankcase, which allegedly degraded the oil and hastened camshaft wear . I am not convinced of this personally, as cam wear problems is STILL the Achilles heel of these engines, despite the deletion of the third row of bolts and the use of composite gaskets.

It is my opinion that the steel shim gaskets are better, as they would not allow this distortion to a similar degree.

If I were ever to build a large bore Rover V8 for myself (unlikely as I hate them now) I would use steel gaskets as fitted to the early 3.9s. I still have two pairs that I am holding on to "just in case" 

Edited August 2 by smallfry
spelling

[Aragorn]

one imagines if you want steel gaskets, you can buy modern MLS gaskets for the Rover V8 fairly readily? 

For me its a bit of a balance of cost. The range rover doesnt get a lot of use, falling very much into the third car for towing the trailer to the dump and running to the DIY store at the weekend. So while the petrol-head wants to go thru it all properly, new cam, fresh lifters, MLS gaskets and head studs etc and build a really nice engine, the frugal scot part is saying "leave it all alone and just fit fresh standard gaskets" because its really hard to justify the expense. If the block is leaking that ofcourse leads to further questions as to whether its worth spending £££ on fixing it properly.

I'll pull and inspect the lifters before i put it all back together just to ensure they're not wrecked though.

If it is a liner leak, i guess i'll try a dose of KSeal or similar.

 

[smallfry]

I have never tried to buy MLS gaskets for it, so I have no idea.

The cost of it all is one of the things why I will not have another one. Also it seems nigh on impossible to get good quality parts for them now is another.

For less money you can convert it to something else that is long term reliable, more economical, and more powerful if thats what you want

 

[Aragorn]

Yeah its a fair point. Though i'm not sure there are any obvious "easy"/"affordable" conversions...

The M57 conversions look nice and the parts are fairly available, but i'm trying to avoid Diesel these days. A truck 5.3 LS would also be pretty sweet and super affordable overseas but sourcing the bits here is very expensive.

Maybe an electric motor is the answer 🤣

[fmmv]

Lexus 1UZFE time?

[Bigj66]

I also had those symptoms in my Thor V8 and when removing the heads for a gasket change noticed the head bolts came out quite easily which I wasn’t expecting. No sign of damage on the gaskets and it’s been fine since so my assumption was that the heads had been incorrectly torqued down during a previous gasket change.

[smallfry]

10 hours ago, Bigj66 said:

I also had those symptoms in my Thor V8 and when removing the heads for a gasket change noticed the head bolts came out quite easily which I wasn’t expecting. No sign of damage on the gaskets and it’s been fine since so my assumption was that the heads had been incorrectly torqued down during a previous gasket change.

Originally the head bolts were supposed to have a low strength threadlock/sealer applied. I don't know if they still are, or new bolts come with preapplied stuff ?

[FridgeFreezer]

On 8/5/2023 at 8:10 PM, smallfry said:

Originally the head bolts were supposed to have a low strength threadlock/sealer applied. I don't know if they still are, or new bolts come with preapplied stuff ?

Never seen that, maybe I never read the manual closely enough - but then I always just bin the head bolts & fit ARP studs anyway.

[smallfry]

1 hour ago, FridgeFreezer said:

Never seen that, maybe I never read the manual closely enough - but then I always just bin the head bolts & fit ARP studs anyway.

Well its there. In the proper factory Rover P5B and P6 manuals, also RRC and 90/110. Applies to the front cover/water pump/inlet manifold bolts too.

Not properly consulting the workshop manual ? Tut tut. Shameful. 

[FridgeFreezer]

4.0 / 4.6 manual says "Lightly lubricate new cylinder head bolt threads with clean engine oil"

[Aragorn]

Fought with the other bank over the weekend. Lots of steam cleaning evident on cylinder 8, piston was completely free of any carbon deposits. Oddly this cylinder also fouls the plugs with oil, so not sure whats going on there.

Some of the cylinders look really bad:

And ofcourse, the camshaft and lifters are knackered. All the lifters are dished and some have fairly heavy groove worn in the middle.

I think given the uncertainty, i'm going to ignore the cam and bores and put it back together with the new gaskets and see how it goes. If the coolant issues are fixed, then i guess i need to give it a camshaft. As for the bores, i guess a compression test and go from there?

The heads are back on. I've ordered new bolts for the exhaust manifolds as those are ruined and are some imperial thread despite being Thor heads (which should be metric seemingly).

Once the bolts arrive i can start reassembling the top end and accessories.

[Aragorn]

Also the head bolts were all well torqued, most required a cheater bar to crack them off. None were obviously loose.

[Aragorn]

So i've had it back on the road for a few weeks... not done huge mileage. Initially it was still using a fair amount of coolant until i noticed it all over the side step... Fixed the poorly clamped hose on the coolant tank and that fixed it.

No longer seeing coolant on the carpet inside (replaced the heater core o-rings) and i'm no longer seeing coolant all over the underside steering bars/panhard rod etc (not even sure where that was coming from, waterpump maybe?), so there are certainly some improvements.

However i've noticed it seems to retain pressure in the cooling system when cold... Nowhere near as badly as before mind, but still...

For instance i topped it off on sunday, with engine etc fully cold. Did a short trip sunday to the local shopping centre then the wife took it to work on tuesday (~15miles total). This morning with the engine fully cold, opening the expansion tank made a loud "tissshhhhh" noise. Water level has dropped a few mm, though cant be 100% sure as the cars not parked on a level surface. I've ordered a pressure gauge as i'm intrigued to see just how much pressure we have.

Logic would suggest it should return to atmospheric pressure when its cooled down unless something is getting in there that shouldnt?

[fmmv]

Could it be a wee bit of a vacuum? So when you fill it there is air in there as well as the coolant( there'll be air dissolved in the water for instance) and then you warm it up by using it - the excess pressure gets burped through the pressure cap, but then you cool it. ( I think some early steam engines worked like that) . Maybe as things settle it'll be OK? The gauge will tell all I suppose.

[Aragorn]

Fairly sure its pressure rather than vacuum. The top hose is notably maintaining pressure. Not rock hard, but a firm springyness that goes away once opened.

The odd thing is its never overheated, the gaskets have been bad and its been pressurising the system for years at this point and the only time i've seen it above 90c was when the rad had a big leak several years back.

I've put off so long because despite the pressure and coolant consumption, its never actually caused any problems. Just a little annoying that i've now fixed it and its still broken, thought i did sort of expect there would be something.