1995 90CSQ Sport...Water Temp Needle Progessively Higher Over Months

[Duncan Thomson]

George,

Chased a similar problem for a long time in my 1988 90Q. It would
overheat and blow all the coolant out of the reservoir.
Not all the time, just occasionally, although the temp trend did get
hotter and hotter over time.
No water in the oil either.

Checked thermostats / fans, etc etc.

Eventually diagnosed by removing reservoir cap and starting engine from
cold. Reservoir was pressurising / bubbling well before the engine had
warmed enough to build steam pressure. Decided at this point that I was
going to have to pull the head.
There was some pitting / corrosion around the top of the cylinder where
the head gasket is supposed to seal. Obviously the cylinder pressure was
leaking into the coolant system and pressurising it, but no water ever
got into the oil.
Also, it only became apparent when the engine was hot. I assume the head
was warping slightly or just from expansion.
Got the head skimmed to clear the corrosion, fitted a new head gasket,
and temp locks at 90deg C now.

So exhaust all other avenues first, but if your reservoir is
pressurising early, it may well be a head gasket job for you.

Hope this helps

Duncan

'86 CQ
'88 90Q

-- 
george.butler2 at verizon.net wrote:
> Hello All,
>
> I acquired a 95 90CSQ Sport a week ago.  I've ordered the AoA/Bentley 
> DVD...but in the meantime I trolling for BTDT's. The previous owner let 
> it go because of an overheating problem ("water temp needle kept 
> creeping up over time...then one day the engine began to 
> steam...'managed to drive it home...engine never seized...it just 
> constantly over-heats now...mechanic [his] thinks it might be cracked 
> head...but there is no coolant smoke coming out of the 
> exhaust...although...a head gasket had been replaced a few months before 
> the major over-heating episode...'water pump was replaced about 10K 
> miles ago". I have receipts to verify previous work.
>
> I've already located numerous diagnostic sequences to pursue in 
> isolating the current over-heating problem...but I'd like to see if 
> anyone on the list could provide an "oh yeah...BTDT...'turns out it was 
> the______" .  Thanks in advance for any input.
>
> Regards,
>
> George B.
>
> 84 4ksq
> 88 5ksq
>