Ah, the joys of a P38.
It's nearly two months since my last coolant-related disaster, so I knew it wouldn't be long. And sure enough... driving along I heard the classic "Pshhhhsssss..." noise as a hose burst, and suddenly steam everywhere.
Yep, this problem:

The hose going to the expansion tank had burst.

Thankfully there was a dealer right up the road... a Holden dealer :-( but after playing around with pipes we found that a radiator hose for a 1975 Holden Cruise was exactly the right diameter, with with right bends and everything! Just a little too long, but I cut it short and popped on a couple of Jubilee clips. And after another hour playing trying to get the airlocks out of my system, I'm back on the road. Look, it fits:

But is this hose bursting a common problem with P38s? Search doesn't throw up much. I'm also starting to wonder if I've got a pressure problem in my coolant system after replacing over the past 6 months the water pump, the radiator, and then having the entire head off after the head gasget blew out one side. How much pressure should I have in the coolant system: when I cap off the expansion tank, the cap would rocket into the bonet, even half an hour after stopping the car, so there is obviously a lot of pressure there?
Oh, and should I replace the Holden parts? It seems to be a lot more solid than the original from Solihull (it was date stamped 1999 so I guess the one that exploded was orginal).

Was going to say check your rad but see you have a new one already. I burst 2 hoses before realising the Rad was blocked. The expansion tank cap can be removed safely after a few minutes after engine has stopped as long as you are slow to release the pressure. My test is to give the top hose a squeeze, if there is give all is well, If its rock hard there is something wrong

No big surprise the hose burst, I have seen plenty of 10-year-old hoses burst. If you haven't already done so replace the pressure cap. The cap should relieve pressure at it's rated value. The Holden hose should be fine, I don't have any problems with genuine Holden stuff as a rule.

A new hose kit containing all the necessary hoses is $110 + p&p for early P38's - a little more for newer ones I think. It's cheap insurance if you've got original hoses on there still ....

Here's the link: HOSE KIT

Thanks! Some of the hoses are original, some replaced... I'll now have a happy weekend replacing every single one, to be safe. And install a low water alarm too P38spares.com used to sell one, but no longer, so I'll chase around for an alternative...

My pressure problems seem to come down to the tiny drain hose on the expansion tank cap being blocked. At least, it was solid with gunk, and now I've got a new one, no pressure problems... Hopefully...

It seem crazy there is no easy aftermarket low coolant alarm. Just incase anyone does not know A common BMW header tank is very similar to the P38 complete with low coolant sender unit. Only hitch is there is one outlet short. The small one at the bottom below the cap area. Now if there was a strong secure way of making that outlet with an adaptor I recon its the way to go.


ORIGINAL BMW E30 325i HEADER TANK on eBay (end time 01-Aug-10 21:26:44 BST)

This:Curve Water Level Sensor Liquid Switch Stainless Steel - eBay Irrigation, Tools, Gear, Equipment, Gardening, Home. (end time 05-Aug-10 18:18:12 AEST)
and a light bulb on the dash?

Has anyone considered using Silicone hoses? they are considerably stronger and longer lasting.

A burst hose can be a symptom of some other problem but the Silicon hose will hold on much longer.

Using this type of float is not practical as the expansion tank has internal baffles. This float must be inserted through the filler hole and out which is not possible without major surgery to the tank.

Agreed - and they're prettier But alas I couldn't find any source for P38 silicone hoses when I was looking and couldn't be bothered stuffing around trying to find 'best fit' ones. Know any source for P38 specific ones ?