The V8 Owners Forum -

OK folks, need some help here, first to confirm my suspicions, then to decide what to do next.

Got a 3.5 that has only done about 800 miles since rebuild. Unfortunately due to faulty stat it overheated twice on the motorway and I'm worried that some damage is done eg. crack in block. There is an annoying ticking on one side after it has warmed up, I'm fairly sure it is using coolant.

Before pulling things apart how do I confirm a cracked block?

My thoughts - drain oil, check for white stuff?, beyond that not sure what else to do. Any suggestions?

If it is indeed a crack what bits need to change other than the block? Would an engine builder rebore a new/relinered block to suit my pistons/rings? I'm guessing just re-linering my block with top hats could still allow coolant into the sump?

Engine has a typhoon cam, ported heads.

Any thoughts much appreciated...

How hot did it get exactly?

Checking for mayo, seeing if the coolant system is over-pressurising (rock hard top hose) and checking compression would be my first steps before getting serious and stripping stuff I think.

How's the oil pressure? My main concerns with an overheat would be things like bearings and rings starting to pick up.

Dropping the oil is an OK thing to do but might not tell you much and if its white you will see it on the dip stick and in the top of the heads anyway. If it comes out white you know you have a problem but if its ok doesn't mean you don't have a problem. It could be leaking into the bore via a crack or a blown head gasket and you would never see it in the oil. Given the overheating on a new engine I would be inclined to blame a headgasket if you do have a problem. Other things you can check are pull the plugs and if you have a leak into the bore the plug that is affected might come out like it has been steam cleaned.

3.5 blocks arent known for cracking, thats generally the 4.0 and 4.6 blocks that do that. Not saying it can't but it isn't common so maybe some comfort there.

Tick is more likely to be a follower, clutching at straws I suppose it could be blamed on a blown head gasket as well but that's a stretch.

Although it's more unusual for a 3.5 to suffer from a cracked block, the fact that it is loosing coolant points to a crack somewhere or a head gasket leak at the ends of the heads. The ticking could be a loose liner clicking up and down or it could just be a cam follower playing up when the oil gets thinner.

You could get the coolant tested for presence of combustion contamination.

Before doing anything drastic, have the cooling system tested *properly* for leaks. Losing coolant could be from a variety of reasons, especially on a new build.

IMHO. it's far more likely to have head or head gasket problems through overheating than a cracked block.

I originally had a 3.5 engine in my Cobra, it used to use a big of water and I used go get quite a bit of crankcase pressure, strangely this only happened once warm.
I never did find the cause, just swapped the engine, but I did think most likely a loose liner though.

Never had it - but if a liner was lose and moving, wouldn't it very rapidly get worse?

Ticking could also be an exhaust manifold gasket leaking

Spongo wrote:Ticking could also be an exhaust manifold gasket leaking

Yes - and not the sort of noise you'd expect with that. To be clear - the head to manifold. And some versions didn't originally have gaskets there at all.

katanaman wrote:Dropping the oil is an OK thing to do but might not tell you much and if its white you will see it on the dip stick and in the top of the heads anyway. If it comes out white you know you have a problem but if its ok doesn't mean you don't have a problem. It could be leaking into the bore via a crack or a blown head gasket and you would never see it in the oil. Given the overheating on a new engine I would be inclined to blame a headgasket if you do have a problem. Other things you can check are pull the plugs and if you have a leak into the bore the plug that is affected might come out like it has been steam cleaned.

3.5 blocks arent known for cracking, thats generally the 4.0 and 4.6 blocks that do that. Not saying it can't but it isn't common so maybe some comfort there.

Tick is more likely to be a follower, clutching at straws I suppose it could be blamed on a blown head gasket as well but that's a stretch.

Sorry for slow reply..ill parents and England Rugby matches meant I did not get near the garage to start doing anything useful! Katanaman's suggestions give me some comfort. I've taken out all the plugs and they are all a nice sandy brown colour with a bit of black carbon around the base of the plug body. Definitely no steam cleaned plugs here. I also notice a slight oil leak which looks to be coming from the base of the nearside head. I've got a small vent on the nearside rocker cover and this is bubbling out liquid (coolant?) when warmed up. I'm thinking (praying) head gasket leak and dodgy tappet only. I'm going to strip off the head on the one side and have a look. Is a blown head gasket obvious? Never done one before...

If this is an EFI engine (or was originally) the vent at the back of the nearside rocker cover is the air inlet to the crankcase. The crankcase is ventilated via the breather system and should be under a slight vacuum when the engine is running. If the breather system is blocked, the crankcase can go positive in pressure and leak oil from the easiest route. Which could be anywhere.

A badly worn engine with piston blow by - or worn valve guides or seals etc - can also pressurize the crankcase.

Hi Dave, its an SD1 engine with old rover P6 type rockers. It's only got one hole on the top and I've got the open breather fitted to that. the other side goes into the base of the air cleaner on the carb. I figured this would draw air in one side due to vacuum from the carb. In reality it seems to like spewing stuff out.....