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87 Nissan 4cyl. Pickup Overheating
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unquity
New User
Apr 5, 2010, 1:30 PM
Post #1 of 7
(1951 views)
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87 Nissan 4cyl. Pickup Overheating
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I hope someone can help diagnose this issue. The truck has 207,000 miles on it. The temp guage started to go up and then would drop back down to normal. This occurred on highway and city. I had the t-stat replaced and it did not help. I had the radiator replaced and that has not helped. The temp guage will go up and drop down randomly and then run at normal temp for maybe a day or so. When the truck runs hot and I've got the heater on, there is no heat from the heater vents. When the truck runs cool there is heat from the heater vents. The truck is running rough as well (although I was told that could be a vacuum leak). I'm also told that it may be the head gasket (replaced it last year). I'm flummoxed! Any ideas?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 5, 2010, 2:37 PM
Post #2 of 7
(1947 views)
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Re: 87 Nissan 4cyl. Pickup Overheating
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Couple may-bees for now why this happens:
* The fan clutch could be erratic and you are really overheating to a boil - note that boiling coolant or air will not exchange heat in the heater core for diddle - takes liquid to transfer the heat.
* The air could just be system is low on coolant and reason why to be found out. Head gaskets can put gaseous vapor into cooling system with same behaviour as low coolant and would barf it out if bad enough and that will cause overheating as well.
Suggest you fill with proper 50/50 mix of coolant at radiator. Run till upper hose is hot and let cool. Feel for pressure before opening cap again (just a squeeze you can tell) when cooled off and fill again if need be. Recovery tank is too slow to only fill from there but have that at proper level as well - a range should be indicated for cold or warm engine on the tank.
Now if problem re-occurs I'd go for pressure testing for leaks.
Other oddities include a water pump that doesn't pump well because of corroded impeller or leaks unseen thru vent at specific pressures that may not make themselves clear. Look for those with a mirror if need be.
Note: Vehicles with fan clutches are temp sensitive as to how hard fan will work. When a warm to hot engine is shut off the fan should stop quickly when engine is shut down or that could be the culprit. Overheating for any reason can cause problems with the head gasket all over again or worse the head itself,
T
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unquity
New User
Apr 5, 2010, 3:09 PM
Post #3 of 7
(1941 views)
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Re: 87 Nissan 4cyl. Pickup Overheating
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Thanks for your reply Tom. I replaced the water pump last year so maybe that could be ruled out. I have noticed some excessive steam from the tailpipe (coolant in there?) and I have had to add coolant frequently, although sometimes after overheating, I've checked and the coolant level is just a tad low. Could a small amount of coolant missing cause the erratic temp changes?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 5, 2010, 3:20 PM
Post #4 of 7
(1939 views)
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Re: 87 Nissan 4cyl. Pickup Overheating
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Arggh! Adding coolant frequently isn't a good sign along with the excessive 'steam' out tailpipe both suggest head gasket issues or as said the head itself.
When cool enough to add thru radiator cap it may seem just a tad low but thermostat is closed locking air on engine side till it opens, air goes out to recovery tank and supposed to draw back only coolant when it cools down but is probably not capable of that.
Spark plugs can be tell tale of coolant evidence. Usually one or more will look markedly cleaner than others as the coolant acts to clean them or if bad enough show the coolant!
I'd be testing away for head/head gasket issues. If you find that so do sent head out to be checked at a machine shop to verify or fix irregularities or condemn it as NG
Good luck,
T
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unquity
New User
Apr 5, 2010, 3:26 PM
Post #5 of 7
(1934 views)
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Re: 87 Nissan 4cyl. Pickup Overheating
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Somehow I just knew things were pointing at the head/gasket. If so, what are your thoughts on keeping it on the road. It has served me well (I'm the original owner). Should I let it die with dignity or try to keep it on life support?
Thanks again for your input. It is most appreciated.
Jeff
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 5, 2010, 3:43 PM
Post #6 of 7
(1931 views)
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Re: 87 Nissan 4cyl. Pickup Overheating
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Well............. Only you can decide to invest in it or cut losses. Still diagnose the heck out of just what it will need for the fix to help you decide. I've had my share of "love affair" vehicles that I way overspent on but it was too sad to see a good friend go - you know what I mean,
T
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unquity
New User
Apr 5, 2010, 3:48 PM
Post #7 of 7
(1925 views)
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Re: 87 Nissan 4cyl. Pickup Overheating
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Yeah, I know what you mean. I've sadly gotten attached to an inanimate object or two in my time!
Again, thanks for your input.
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