Strange cooling problem...


robthedoc

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Hi guys I'm having an issue with the expansion bottle filling up and the car running slightly higher temps, about 96-99 degrees. It doesn't over heat but definitely runs hotter than I would like. When the bottle fills up it doesn't go back down when the engine cools down, like right down over night. I'm thinking/hoping that the rad cap might be faulty? seems to be when temps go up and pressure rises coolant expands out into the bottle but when temps reduce the coolant is not taken back into the radiator this causing the coolant level to be lower than it should be... runs hotter? If I pour the coolant out the bottle back into the rad it runs cool again until it gets driven aggressively. Has anyone had anything like this before? Its a mishimoto radiator. Maybe also worth saying the temp gauge on the dash seems to be a bit unstable seems to rise and fall quite a bit. Seems to drop under boost?

Please don't say head gasket
 




elchunk

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no air in the system? sounds like there is a pressure build up on the top hose and its forcing the fluid out into the expansion bottle.
 


robthedoc

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Looking like it man. Just pressure tested the cap and its opening at 19 psi. Return valve opens really easily as well.
Not looking good
 


b16 mini

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Am I right thinking you used arp main studs and had to line hone your block?

Did you re surface the block at the same time as I think it's possibly advised to do so?

Worth trying a block test kit on it
 


robthedoc

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Yeah man using arp main and head studs, the block was line bored for the mains and surface ground to ensure flatness also overbored to 81.5mm. With the head it was ground to ensure flatness, pressure and vac tested and new guides. Using a Cometic MLS head gasket. I have a block tester at the garage and tested the expansion bottle last night and it was fine. I will do the radiator instead tomorrow.
 


Vtec6000

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Cometic headgasket is probably your issue! I've seen a fair few of them fail on Honda's and other cars. Change to a OEM Honda HG.
 


robthedoc

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@Vtec6000 aonghus will a standard gasket do it or do I need to get a oem .5 oversize? really need it this week so it's ready in time
 





jesse888

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Shame to hear more issues bud, I've also heard about the cometic gaskets but my first build was fine(for how long it lasted)
Been using oem Honda since then.
 


robthedoc

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I know man it's a bit gutting but I'd rather work out the bugs now before it really starts working hard. I'm now in a good position to say I wont be using cometic stuff again.
 


jesse888

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Yeah just work the bugs out and you'll be fine. Like you say start working it hard and the bugs just get bigger or more troublesome.
Not like it's a hard job to crack the head off and replace the gasket, more of a pain than anything else.
strange it doesn't drain back into the radiator though?
Have you checked the line from the bottle to the cap(including inside the bottle) for any tears or holes? Thinking air leak stops the fluid draining back in?
 


robthedoc

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I checked it all mate I was really hoping to avoid changing the gasket but I can't deny that's where the problem is coming from. Was clutching at straws really. The boss of the engineering department was showing me a book called ' thermodynamic and transport properties of fluids' yeah man he keeps that on his desk haha. There is a chart in it showing the temp and pressure relationship, for the cap to open due to expansion of the coolant, the coolant temp would be 124.9 degrees C to overcome the 1.3 bar cap pressure. I'm seeing 99C max so the pressure isn't being caused by the coolant expanding. Lucky though as I got a genuine Honda head rebuild kit and the only bit I didn't use was the head gasket, got loads of coolant left too so it's just time needed and this is great because I have limited funds atm.
 


jesse888

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Haha just keeps that book there for casual reading in his downtime lol
Lucky to have such a knowledgeable chap you can talk to tbf.
Cheap fix then really if you've got all the parts needed. Weird you've had no luck with cometic, all of mine where fine and I'm sure we used the same gasket kit.
Although I didn't run mine for long so that may well be why.

You mapped this yet or still running it in?
 


robthedoc

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I think it's odd that all three parts failed out the street pro kit. Might of been an old set or something who knows. Anyway this is the last bit of cometic in there and it's coming out. Hopefully there nothing more sinister in there causing this but everything was machined and cleaned and checked and checked. Kind of between base map and full map atm. Aonghus is over in two weeks and I'm booked in on Tuesday 15th. The clock is ticking haha.
 


jesse888

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Haha good stuff.
Bet you can't wait!
 


robthedoc

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Mate it's been a long time coming... Ive went into rocky balboa mode. got a pic of a mates focus rs on the bathroom mirror hahaha
 


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