OK what causes these to fail? as i think the thermos has failed again with in a month of replacing it.

 

the replacement was a genuine OEM part

My money is still on there being another blockage and I reckon a good rad flush or two will sort it out. If you don't want to fork out on one try the washing powder idea, I just looked and it contains caustic soda like the rad flush, it wont do any harm and is alot less effort than pulling the engine.

 

Do you know when the water pump was last changed? The impeller might have corroded so there is no water being moved, what do you think?

My money is still on there being another blockage and I reckon a good rad flush or two will sort it out. If you don't want to fork out on one try the washing powder idea, I just looked and it contains caustic soda like the rad flush, it wont do any harm and is alot less effort than pulling the engine.

 

Do you know when the water pump was last changed? The impeller might have corroded so there is no water being moved, what do you think?

 

pump was changed last week, so far since the original thermostat failure ive changed.

 

thermostat twice, water pump for a new one. one blocked radiator for a clean one (albeit it did leak, but not sure how well that seal is, its not leaking but doesnt mean its not drawing air into the system)

Put the washing powder through it mate, at the end of the day, it isn't going to hurt it is it really? Plus, if you're thinking about torching or crushing the car, you've nothing to lose whatsoever. Get the washing powder through it and hope bud. Don't start ripping the engine apart before you can be certain, if there's nothing wrong with the head gasket, you'll still have a broken car and be kicking yourself.

As I am sure you have become a dab hand at changing the thermostat and for a test of flow rate remove the stat completely, should not take long and although not a fix may render the car usable in the short term.

 

Jeff

might as well chuck something in have you done the water bypass on the engine ?

maybe the pipe is failing was it a sil or rubber fuel pipe [fuel pipe is what I used]

also could the matrix be blocked ?

 

things to try if you have done the bypass would you be able to fix up a pipe to the matrix

out let turn engine over see if you get a good stream of water out this would also let you know if the water pump is doing what it should

right had a little thought, going over all the images of my crudded up rad, im going to do a heater matrix bypass and see if it still over heats, have a funny feeling that once id changed my radiator over due to blockage and i got the flow back, the little radiator has clogged up and is now causing me to lose flow so i cant bleed the system correctly.

 

If this fails to work then its most likely HG fault. but if my assumption is correct. this should sort it out until i can change the Heater matrix or at least give it a good flush through.

 

When i changed the rad, it ran fine for about 2 hours while testing it, even giving it boost and everything, the next day when i started the car, it just overheated while on idle, though never reaching more than 105c as i turned it off before then.

try the heater matrix then i think you really should do a leak down just to put the whole h/g thing to rest one way or the other esp before you go tearing the block apart mate.

ok took the pipes off the heater matrix, if going by the state of the rubber pipes is concerned the heater matrix is going to be clogged.

 

does anyone know what diameter pipe i need to do the by pass, i tried it with the pipes i took off, but they just collapse when bending so will not do.

I'd ask Anthony D that one mate, I think they're actually different diameters at each end too, where you'll want one that's the same diameter at each end to do the bypass.

I'd ask Anthony D that one mate, I think they're actually different diameters at each end too, where you'll want one that's the same diameter at each end to do the bypass.

 

no point for something thats going to be temporary. heater matrix isn't leaking but does need a clean, so may as well get a primera one and change it over before the really cold weather comes, don't want to be freezing me butt off in the zed, well thats if it is a blocked core on the heater matrix thats causing my over heating.

As I am sure you have become a dab hand at changing the thermostat and for a test of flow rate remove the stat completely, should not take long and although not a fix may render the car usable in the short term.

 

Jeff

 

only just noticed this post from you matey, to say i can strip the front of the engine in about 5mins and get the thermostat out is a understatement lol

 

But i have a suspicion that my heater matrix may be blocked.

My Matrix was proper blocked for about 2years and i was pissed off in winter because it was bloody freezing and i was driving around everywhere with aircon on :lol::lol:

 

Look at my 1st ever posts lol!!!

 

But i never had any overheating issues. I took my matrix out and attacked it with a hose pipe. THe hose pipe fitted just inside the matrix tube perfectly, switched it on full bore and it took about half an hour for everything to come out and now im nice and tostie

 

I cannot remember the diamiter, think its about 16mm iirc?

Yeah the matrix hoses are tapered. One end larger than the other, have you tried flushing the block?

only just noticed this post from you matey, to say i can strip the front of the engine in about 5mins and get the thermostat out is a understatement lol

 

But i have a suspicion that my heater matrix may be blocked.

 

The heater matrix been blocked will have no bearing on the overheating, the matrix is fed by a secondry water circuit, and in any case when the heater is switched to cold under normal circumstances it shuts the valve and this closes the circuit.

 

If your worried about the heater been blocked making it harder to get the air out just loosen one of the heater pipes and run the engine at idle and when water comes out its bled.

 

In fact the whole air bleed debate I have seen here and numerous times is not fact, remember we change cambelts regularly and whilst owners wait in the shop, bleeding the air out is never a problem, it is simply a case of filling as much as possible then running the engine ( heater on 40 if working) and adding coolant as required, after 10 mins or so switch it off and wait 5 mins, do this three times and its done, a run around the block and check the water level again, this is applicable to twin turbo`s as non turbo`s have a different rad design that aids bleeding to a point that you can practically fil lit up from cold.

 

 

Jeff TT

The heater matrix been blocked will have no bearing on the overheating, the matrix is fed by a secondry water circuit, and in any case when the heater is switched to cold under normal circumstances it shuts the valve and this closes the circuit.

 

If your worried about the heater been blocked making it harder to get the air out just loosen one of the heater pipes and run the engine at idle and when water comes out its bled.

 

In fact the whole air bleed debate I have seen here and numerous times is not fact, remember we change cambelts regularly and whilst owners wait in the shop, bleeding the air out is never a problem, it is simply a case of filling as much as possible then running the engine ( heater on 40 if working) and adding coolant as required, after 10 mins or so switch it off and wait 5 mins, do this three times and its done, a run around the block and check the water level again, this is applicable to twin turbo`s as non turbo`s have a different rad design that aids bleeding to a point that you can practically fil lit up from cold.

 

 

Jeff TT

 

thing is though, it will cool down and run at a stable temperature when its blowing hot air, but soon as it starts blowing hot air (even when the temp is set on 35 with the fan full and not autoing), the temp rises until i either get hot air or i shut it off.

 

Now when i changed the radiator, i got the flow back through the thermostat, I've checked the old one i took out yesterday and thats still functioning like it should, the after the initial run with the new radiator in, i not only had hot air blowing through the air vents, but the car didn't over heat, left it over night and tried it again the next day, and it just tried to over heat and i got no hot air through the heater matrix, the top feed pipe from the engine to the lower matrix was hot, but the bottom one that feeds the top of the heater matrix was cold, and i just couldn't get any hot air out of the system, it just stayed warm then went cold as the engine temperature started creeping.

 

Ive read up on overheating on the Aus300zx site as they seem to get more overheating problems due to the climate they live in compared to the UK.

 

Id have thought that if it was the HG, that it would over heat regardless of if i had hot air through the heater or not, which just isn't the case.

 

According to the Service manual the heater core is fed from the cylinders and back out into the thermostat housing. surely a major blockage in the heater matrix would restrict the flow and upset the system, other wise a heater matrix bypass would just be better to block both pipes instead of looping them?

Edited December 5, 201114 yr by vodkashots

The water flow scematic show shows the matrix circuit a bit simplistically but correct in its ability to be shut off by the heater valve and have NO effect on a correctly running engine.

 

Jeff TT

 

The water flow scematic show shows the matrix circuit a bit simplistically but correct in its ability to be shut off by the heater valve and have NO effect on a correctly running engine.

 

Jeff TT

 

 

did what you said about removing the heater hose on the back with engine running, no water dry as a bone yet i cant get any more in the rad, and still no heat, (disconnected the pipe closest to the drivers side.

 

Do i have a blockage else where then? as doesnt seem to be any flow.

 

im just miffed how it can go from being over heating to fine with heating to over heating again with no hot air?

Edited December 5, 201114 yr by vodkashots

ok plan of action, spoke to jimmer today, who says if its HG then the rings will most likely fail after and he wouldn't want to risk it for me, which is totally fair.

 

I could split the car and with the proceeds get a new zed with no engine work, but every time i look out the window i really don't want too.

 

Or i could get a new engine, change the cam belt on it, change the thermostat water pump, pulleys belts and what not, and stick that in with my manual conversion kit that im still yet to fit.

 

So Wednesday going to order a block tester, though i think i know what its going to say, and go from there.

 

selling it just isn't a viable option, its worth a lot more in parts than what i got offered for it. so looks like im going to be in it for the long haul on this one.

 

Just a crapper that i don't have a car over the winter period for the kids.

 

i just cant bring my self to give up on the old girl with out a good fight.

Good on you mate! I reckon pull the motor, break down the two spare motors you've got in the garage and rebuild one decent motor from all three, that's gunna cost less than buying a replacement motor that you never know, might have it's own problems.

Good plan dude, you do mean a compression test kit when you say block tester? I still think you should just flush the bloody system out lol, go on, get the washing powder out :yes:

Good plan dude, you do mean a compression test kit when you say block tester? I still think you should just flush the bloody system out lol, go on, get the washing powder out :yes:

 

nope not compression test, block tester is blue liquid that turns green or yellow if hydrocarbons are present in the radiator

 

Compression test most likely wouldn't pick up a hairline crack in the cylinder to water galley wall thats letting combustion gases into the water system.

 

You can also find out what cylinder is leaking with it, called a leak down test, where by you take the plugs off all the cylinders on one bank, test it again and see if your getting the color change, if your not getting the color change, then the leak is on the other bank, you can then go through each cylinder on the other bank testing one by one using the radiator to find out where its leaking from.

 

Compression test will just give me the compression across each cylinder, but with a 20 year old engine, it may be low on some anyway.

 

Hollow point, if i get another engine, im hoping its going to come from zed world so at least i know its a good one.

 

But i know what, what ever engine i get, first thing thats getting changed is the bloody thermostat. annoying when a £20 part can knacker your engine when it fails.

block tester

http://www.ebay.co.uk/itm/BLOCK-TESTER-KIT-GASKETS-CYLINDER-HEADS-BT500-/160684455155?pt=UK_Diagnostic_Tools_Equipment&hash=item25698a34f3

Ah nice, I was looking for one of these not long ago but cheapest I found was about £70.

 

Do you have a plan on what you going to do about the blocked water passage, or awaiting Jeff's response?

Ah nice, I was looking for one of these not long ago but cheapest I found was about £70.

 

Do you have a plan on what you going to do about the blocked water passage, or awaiting Jeff's response?

 

you mean the heater matrix, well as that will need doing, plus im going to do the manual conversion, ill take the dash out as its only 10 bolts and do it all at the same time, may even rewire my bloody wing mirrors that don't work while im there.

you mean the heater matrix, well as that will need doing, plus im going to do the manual conversion, ill take the dash out as its only 10 bolts and do it all at the same time, may even rewire my bloody wing mirrors that don't work while im there.

 

I thought there was no water going into the matrix from the engine indicating a blockage inside it, or did I get myself confused?:wacko:

 

If you do (but hopefully don't) go down the engine rebuilding route let me know and i'll come and give you a hand if im up to date with work and can be of assistance