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Coolant issue! leaking out of thermostat housing bolts :(
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Author:  MiniMe87 [ Thu Jul 29, 2010 1:38 pm ]
Post subject:  Coolant issue! leaking out of thermostat housing bolts :(

Hi All,

after running my car for no more then acouple of mins i get coolant leaking out from underneath the head of one of the bolts in the thermostat housing?? asny ideas?? any ways of fixing this?

Cheers All!

Author:  Hanra [ Thu Jul 29, 2010 1:42 pm ]
Post subject: 

Replace your thermostat gasket, ensure the gasket housing is not corroded or warped around the mounting face.

Author:  MiniMe87 [ Thu Jul 29, 2010 2:02 pm ]
Post subject: 

how hard is it to drill and tap a new thread in there? as one of the bolts (not the leaking one though) once you start tightening it up slips back a thread, so can not be tightened totally.

Author:  Hanra [ Thu Jul 29, 2010 2:11 pm ]
Post subject: 

Can you try a longer bolt? Or is the one you have bottoming out already?

Author:  Mick [ Thu Jul 29, 2010 3:08 pm ]
Post subject: 

When you have stripped a thread and can't get a longer bolt to bit, then its best to have the thread helicoiled ( A proprietry name, there are other terms for it). This means the hole is oversize drilled a little, a tap run into it and a stainless steel thread inserted. The new thread is strong and permanent.

You can get a workshop to do it, or if you feel capable of doing it yourself then the kit costs about 45 dollars which includes the drill, tap, thread insert and tool. They're available from hardware suppliers like Blackwoods, or bearing suppliers like CBC bearings or SKF. Also can be had on eBay.

The thread size here is 5/16 UNC.

If it is the stud or bolt that is stripped, then these are easily replaced.

Author:  minimanic [ Thu Jul 29, 2010 3:28 pm ]
Post subject: 

I've found quite a few times that the coolant leaks up past the threads in the head, along the shank and out the top of the housing. If this happens I now slip a small 'O' ring on the stud between the housing and a flat washer.
Never had a leak after doing this! :D
Mind you, it won't fix a dodgy thread!

Author:  headgasket [ Thu Jul 29, 2010 3:47 pm ]
Post subject: 

If it helps anyone, when I replaced my radiator, some old gasket or whatever gunk was circulating in the coolant sat inside the thread. When I went to reinstall the housing, as I tightened one of the outer bolts, the casting started to crack from the hole! Leaks++ So make sure the threads are clean.

Author:  jimmyinamini [ Thu Jul 29, 2010 5:12 pm ]
Post subject: 

headgasket wrote:
If it helps anyone, when I replaced my radiator, some old gasket or whatever gunk was circulating in the coolant sat inside the thread. When I went to reinstall the housing, as I tightened one of the outer bolts, the casting started to crack from the hole! Leaks++ So make sure the threads are clean.
and do not try to use a larger diameter bolt whatever you do i say recoil and if your thermo housing is pitted and s hite i sugest using some grey silicone or something but dont go overboard with it you dont want it cloging things up .

Author:  Drexxle [ Thu Jul 29, 2010 5:18 pm ]
Post subject: 

if you have cooling problems, water turns to steam, and is thinner and can more easily escape. Make sure you are running at the right temps, no blockages, using coolant etc.

Author:  drmini in aust [ Thu Jul 29, 2010 5:18 pm ]
Post subject: 

You can still buy new thermo housings, there is no excuse for using a brittle & crumbling old relic.
There are 2 sorts of gaskets-
Paper (ie gasket material), or cork.

I found the cork is crap, it tends to squeeze outwards then you get leaks up the studs.

These days I use 5/16 UNC Unbrako socket head cap screws not studs, and I coat the threads in Permatex/Loctite #3 gasket cement. They come out easy and don't get jammed in the housing like studs do if corrosion sets in. Or break off.....

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