Isuzu 52 header tank cap

[bigeyerex]

Hi people, I want to replace my cap but there isn't any markings on it, I found one on ebay which says it fits all marine Isuzu engines and shows its 14lb ,has anyone sourced an alternative, its a 42hp engine

Edited December 24, 2015 by bigeyerex

[Neil Smith]

That should be fine, but just keep an eye on the temp for a day or so.

 

Neil

[Flyboy]

Hi people, I want to replace my cap but there isn't any markings on it, I found one on ebay which says it fits all marine Isuzu engines and shows its 14lb ,has anyone sourced an alternative, its a 42hp engine

14 psi is correct. (95 KPa)

[bigeyerex]

Cheers guys , but has anyone sourced a replacement from another vehicle

[Tony Brooks]

Cheers guys , but has anyone sourced a replacement from another vehicle

 

The pressure rating should en stamped on it so you just need to quote the pressure rating and then check the length of the springy bit. That should be OK for most motor factors but not for the idiots in halfrauds.

[bigeyerex]

That's what I was thinking, just easier if someone has already cross matched with a certain car ?

[ditchcrawler]

 

The pressure rating should en stamped on it so you just need to quote the pressure rating and then check the length of the springy bit. That should be OK for most motor factors but not for the idiots in halfrauds.

I rifled through the bins in halfrauds and found one for my engine

[raymondh]

Hi, Lots of BL cars use 13/15 psi caps 14psi is rare and I am sure the tech is not there to be a problem so I would go for a BL at 13 or 15 as the cost is circa £3 You could work out the temp diff between 13,14, and 15 psi but why bother the tolerance is provably more

 

Ray

Edited December 30, 2015 by raymondh

[ditchcrawler]

This set me searching and made me wonder who decides what the pressure should be. I have a Beta BD3 engine and I can't remember what the cap was I took off, I think it may have been about 14psi but the engine manufacturer Ford says its only 4 psi

[Tony Brooks]

It should be the designers who designed the engine and cooling system. Despite what may say the only reason to pressurise the cooling system is to prevent the coolant boiling on the internal hot spots, mainly in the head, like around the exhaust valve seats. BY pressurising the water can run hotter so the temperature difference between across whatever type of heat exchanger you use is greater so more heat can transfer.

 

If we ignore the somewhat silly rubber end caps on some marine manifolds I doubt having an excessively high pressure will do any harm as long as the hoses stay in place and nothing leaks. I strongly suspect that given a suitable heat exchanger/skin tank size most inland boats could run with lower pressures than the same engine in automotive or industrial use because the engine loads are lower but I would not count the likes of NC as an inland boat.

[NBDensie]

When the rubber seal on my Isuzu 35 radiator cap split I took the cap round to a specialist car parts guy who thought he had one similar. After a bit of searching he came back with one which has worked fine for the past few years- apparently it was specified for a 1970's Vauxhall Royale!

[bigeyerex]

I've bought one today its an Austin 13,lb one just over £3 ill give it a try, as someone has said the pressure isn't that high, the one that was on it was a 15 lb I rubbed a pencil over a piece of paper on it and the figures emerge from the rust, its gotta be better than the one I had as it had part of the rubber split ?

[ditchcrawler]

You are not going to see the difference